Defendants Anthem Life Insurance Company (“Anthem”), Wellpoint, Inc. (‘Wellpoint”) and Wellpoint Flexible Benefit Plan appeal the district court’s order reversing Defendants’ denial of long-term disability benefits for Plaintiff Ruth Mitzel (“Mitzel”). Mitzel brought this enforcement action pursuant to the Employee Retirement Income Security Act of 1974 (“ERISA”), 29 U.S.C. § 1001 et seq., after the health plan administrator denied her claim for long-term disability benefits. On appeal, Defendants argue that the district court erred in finding that the administrator’s decision had been arbitrary and capricious. For the following reasons, we AFFIRM the order of the magistrate judge.
BACKGROUND
I.
A.
On March 15, 2004, Mitzel began working for Anthem, a subsidiary of Wellpoint, and joined Wellpoint’s Flexible Benefit Plan (the “Plan”). Anthem was the Plan’s administrator, with discretionary authority to interpret the Plan and final authority in reviewing claims and appeals.
The terms and conditions of Mitzel’s long-term disability benefits under the Plan are contained in three separate documents. The first document, titled “Anthem Flexible Benefits Plan and Summary Plan Description” (the “Summary Plan Description”) provides a general, condensed guide to Wellpoint employees’ health benefits and coverage. The first page of the Summary Plan Description states: “This document, together with the incorporated documents listed in Exhibit C, constitute the written plan document required by Section 402 of ERISA and the Summary Plan Descriptions required by Section 102 of ERISA.” (Administrative Record (“AR”) at 358.) Exhibit C of the Summary Plan Description is a list of the Plan’s eight component benefit programs, including the Long Term Disability Benefit Program (the “LTD Benefit Program”). A one-sentence preface to this list of programs states: “Component Benefit Pro*76grams are available on the HR intranet site unless otherwise noted.” (AR at 387.) The LTD Benefit Program is a separate thirty-five page document which describes the conditions for long-term disability benefits as follows:
We will cover your disability if it is caused by, contributed to by or results from a pre-existing condition and your disability begins after you have been insured for 12 consecutive months after the effective date of coverage. If you do not meet this time period requirement, your disability is excluded from coverage under this plan.
Pre-existing condition is a sickness or injury:
for which you received treatment;
OR
where symptoms were present to the degree that an ordinarily prudent person would seek treatment; within the three months prior to your effective date of coverage.
Treatment includes:
consulting with a doctor
receiving care or services from a doctor or from other medical professionals a
doctor recommends you see
taking prescribed medicines
being prescribed medicines
you should have been taking prescribed
medicines but chose not to
receiving diagnostic measures.
(AR at 404-05) (formatting in original, with bullets omitted). The LTD Benefit Program defines “effective date of coverage” as ninety days after the employee has begun active employment, or June 13, 2004 in Mitzel’s case. (AR at 392.)
A third relevant document, entitled “Long-Term Disability: 2005 Benefit Booklet” (the “LTD Benefit Booklet”) and consisting of eleven pages, was also available for Plan participants. The LTD Benefit Booklet includes a preface that states “Together with the Anthem Flexible Benefits Plan and Summary Plan Description, this document constitutes the written plan document required by Section 402 of ERISA and the Summary Plan Description required by Section 102 of ERISA.” (AR at 348.) The LTD Benefit Booklet includes a section on pre-existing conditions which states:
During your first 12 months of coverage, you will not be eligible to receive disability benefits if your disability is caused by, contributed to by or results from a pre-existing condition. A pre-existing condition is a sickness or injury for which you received medical care or services (including doctor visits, prescriptions and diagnostic tests) during the three months prior to your effective date of coverage.
(AR at 350.) The last page of the LTD Benefit Booklet includes the following disclaimer: “In case of any conflict between this booklet and the Plan document, the provisions of the actual Plan document will prevail. It is your responsibility to read, understand and comply with the policies described in this Summary Plan Description (SPD).” (AR at 357.)
B.
In January 2004, during an annual physical with her primary care physician, Mit-zel reported that she was experiencing hip pain. Her physician referred her to Dr. Rafael E. Arsuaga (“Dr. Arsuaga”), who met with Mitzel on March 2, 2004. Following this visit, Dr. Arsuaga wrote to Mitzel’s primary care physician that Mitzel “presents with acute onset of symptoms dating October of 2003 when initially she experienced right shoulder pain followed by right lateral shoulder pain and neck pain, low back pain, left hip pain and gen*77eralized malaise lasting several hours despite the use of NSAIDs in the past.” (AR at 137.) Dr. Arsuaga also stated that “positive antinuclear antibody speckled pattern, young female with arthralgias might suggest the possibility of SLE [Systemic Lupus Erythematosis] but I would expect to see much more criteria before we could assure the diagnosis. Other possibilities to consider in the differential diagnoses are rheumatoid arthritis, acute thy-roiditis.” (AR at 138.) Mitzel met with Dr. Arsuaga again on March 25, 2004 and April 2, 2004, displaying a rash on her arms and thighs for the first time. After the March 25, 2004 visit, Dr. Arsuaga took a note that he was now “considering] more strongly the possibility of SLE,” and recommended to Mitzel after the April 2, 2004 visit that if her symptoms persisted, she should see an ear-nose-and-throat surgeon for a biopsy. (AR at 139.) Dr. Ar-suaga continued to suspect SLE and recommended a biopsy after meeting with Mitzel again on May 6, 2004.
Upon receiving Dr. Arsuaga’s reports assessing Mitzel and seeing no improvement, Mitzel’s primary care physician then referred her to the Cleveland Clinic. On June 18, 2004 — five days after her effective date of coverage under the Plan — the Cleveland Clinic diagnosed Mitzel for the first time with Wegener’s granulomatosis (“WG”), a life-threatening condition affecting multiple organs.
On June 3, 2005, Mitzel was hospitalized as her WG deteriorated, and accordingly took short-term disability leave from work. On November 1, 2005, with her short-term disability benefits exhausted, Mitzel submitted a claim for long-term disability benefits. By letter dated May 18, 2006, Anthem denied Mitzel’s claim. In the letter, Anthem cited the definition of “pre-exist-ing condition” in the LTD Benefit Booklet, and noted Mitzel’s three visits with Dr. Arsuaga during the three-month look-back period of March 13 to June 13, 2004. Although Dr. Arsuaga had never considered the possibility that Mitzel had WG, Anthem nevertheless advised Mitzel that “[a]s you were having symptoms of your condition and consulted with Dr. Arsuaga during the pre-existing time frame, your condition qualifies as pre-existing and is excluded from coverage under the plan.” (AR at 114.)
On June 8, 2006, Mitzel appealed the Plan’s denial of long-term disability. In reviewing Mitzel’s appeal, Anthem retained an “independent physician specialist,” Ronald J. Bloomfield, to evaluate Mit-zel’s medical history and claim. (AR at 83.) Dr. Bloomfield concluded:
Ms. Mitzel became ill in October 2003 with [WG]. She had multiple medical visits prior to, during, and after her preexisting time period. She was being examined by Dr. Arsuaga in March and May 2004 for symptoms which were eventually diagnosed as [WG]. She became symptomatic from [WG] in October 2003 and was not diagnosed nor treated until June 2004. The failure to make the diagnosis until a few days after her pre-existing time period ended is noted. However, she was being examined by Dr. Arsuaga for symptoms which were caused by [WG].... The fact that the diagnosis was not confirmed until after she was hospitalized in June 2004 does not change the fact she was in the midst of an evaluation prior to her becoming so ill that she required a lengthy hospitalization.
(AR at 93.) Based on Dr. Bloomfield’s assessment, the Plan upheld the denial of Mitzel’s long-term disability benefits.
Mitzel made a final appeal to Anthem, submitting letters from Dr. Arsuaga and the shoulder specialist who first evaluated her shoulder pain in October 2003. Dr. *78Arsuaga stated in his letter that when he evaluated Mitzel in March and May 2004, Mitzel did not meet the criteria for WG. The shoulder specialist stated, “Her problem at that time was for an acute shoulder impingement tendonitis, which improved by her last visit with me on 12/4/03. Her problem of shoulder impingement tendonitis is not a pre-existing condition to her current diagnosis of [WG].” (AR at 50.) Anthem hired another independent physician to assess Mitzel’s claim based on her medical records. The independent physician confirmed Dr. Bloomfield’s opinion, and by letter dated February 1, 2007, the Plan Administrator denied Mitzel’s final appeal for the same reasons it previously stated.
C.
On July 3, 2007, Mitzel filed this ERISA enforcement action against Anthem and Wellpoint in district court, later amending her complaint to add Wellpoint Flexible Benefit Plan as a third Defendant. On October 23, 2007, the parties consented to the jurisdiction of a magistrate judge with respect to all issues, including dispositive rulings. On February 15, 2008, Defendants moved the court to uphold the denial of benefits, and Mitzel cross-moved for summary judgment in her favor.
On July 14, 2008, the magistrate judge granted Mitzel’s motion for summary judgment and overruled the administrator’s denial of Mitzel’s long-term disability benefits, because he found Defendants’ interpretation of “pre-existing condition” in the Plan to be arbitrary and capricious. Noting that the Plan’s definitions of “preexisting condition” in the LTD Benefit Program and the LTD Benefit Booklet were different, the magistrate judge stated that “[t]he court rests the decision on the definition in the [LTD Benefit Booklet], which had been quoted in the initial denial letter. Plan summaries generally trump the language of the plans themselves.” (Record on Appeal at 340.) The court then found that the definition of “pre-ex-isting condition” in the LTD Benefit Booklet was ambiguous with respect to whether it applied to a condition for which symptoms were recognized during the look-back period, but for which there had not been an accurate diagnosis or even a suspicion of the actual condition. The court then applied the rule of contra proferentem— that ambiguities must be construed against the drafter of the ambiguous language — to find that the denial of benefits based on this language was arbitrary and capricious. Defendants timely appealed.
II.
This Court reviews de novo a district court’s decision to grant summary judgment upholding or reversing a denial of health benefits pursuant to ERISA. Killian v. Healthsource Provident Adm’rs Inc., 152 F.3d 514, 520 (6th Cir.1998).
When an ERISA plan grants the plan administrator discretionary authority to determine benefit eligibility, the district court must review the plan administrator’s decision under the arbitrary-or-capricious standard. Firestone Tire & Rubber Co. v. Bruch, 489 U.S. 101, 115, 109 S.Ct. 948, 103 L.Ed.2d 80 (1989); McDonald v. Western-Southern Life Ins. Co., 347 F.3d 161, 168 (6th Cir.2003). In this case, the Plan states that Anthem has “the full power to make factual determinations and to interpret and apply the terms of the Plan as they relate to the benefits provided through this self-funded Plan.” (AR at 379.) The parties do not dispute that the Plan grants discretionary authority to the Plan’s administrator, and that the arbitrary-or-capricious standard should therefore apply.
*79“This [arbitrary and capricious] standard is the least demanding form of judicial review of administrative action. .. .When it is possible to offer a reasoned explanation, based on the evidence, for a particular outcome, that outcome is not arbitrary or capricious.” Killian, 152 F.3d at 520. Under this standard, this Court “will uphold the administrator’s decision ‘if it is the result of a deliberate, principled reasoning process and if it is supported by substantial evidence.’ ” Glenn v. Metropolitan Life Ins. Co., 461 F.3d 660, 666 (6th Cir.2006) (quoting Baker v. United Mine Workers of Am. Health & Ret. Funds, 929 F.2d 1140, 1144 (6th Cir.1991)), aff'd, — U.S. —, 128 S.Ct. 2343, 171 L.Ed.2d 299 (2008). Yet while arbitrary and capricious review is deferential, it “is no mere formality[,]” and must consider “the quality and quantity of the medical evidence and the opinions on both sides of the issues.” Glenn, 461 F.3d at 666 (quotations and citation omitted). “While a benefits plan may vest discretion in the plan administrator, the federal courts do not sit in review of the administrator’s decisions only for the purpose of rubber stamping those decisions.” Moon v. Unum Provident Corp., 405 F.3d 373, 379 (6th Cir.2005).
Moreover, this Court may consider, as “a factor ... when determining whether the administrator’s decision to deny benefits was arbitrary and capricious,” the conflict of interest that exists when the insurer both decides whether the employee is eligible for benefits and pays those benefits. Evans v. UnumProvident Corp., 434 F.3d 866, 876 (6th Cir.2006). In considering this factor, “[t]he reviewing court looks to see if there is evidence that the conflict in any way influenced the plan administrator’s decision.” Id. (citations omitted). Through its Anthem subsidiary, Wellpoint both funds and administers the Plan, and therefore acts under this conflict of interest. However, Mitzel does not argue before this Court that the conflict influenced the denial of her disability benefits, and has provided no evidence of bias. Accordingly, we place little emphasis on this factor, though we note that where an insurer funds and administers a plan, “there is an actual, readily apparent conflict ... not a mere potential for one.” Killian, 152 F.3d at 521.
“[A]bsent a procedural challenge to the plan administrator’s decision, this Court’s review is limited to the administrative record of the benefit determination.” Evans, 434 F.3d at 876.
III.
The magistrate judge, in determining whether Anthem’s interpretation of “preexisting condition” was arbitrary and capricious, considered only the definition in the LTD Benefit Booklet, because “[p]lan summaries generally trump the language of the plans themselves.” (ROA at 340.) On appeal, Defendants argue that the magistrate judge impermissibly ignored the Plan’s other documents in focusing exclusively on the LTD Benefit Booklet.
ERISA requires a plan provider to distribute a summary plan description to all participants and beneficiaries. 29 U.S.C. § 1021(a)(1). The summary plan description must “be written in a manner calculated to be understood by the average plan participant, and shall be sufficiently accurate and comprehensive to reasonably apprise such participants and beneficiaries of their rights and obligations under the plan.” § 1022(a). Defendants have not disputed that the relevant “summary” document for the purposes of § 1021(a)(1) is *80the LTD Benefit Booklet.1
“This Circuit has decided that statements in a summary plan are binding and if such statements conflict with those in the plan itself, the summary shall govern.” Edwards v. State Farm Mut. Auto. Ins. Co., 851 F.2d 134, 136 (6th Cir.1988); Haus v. Bechtel Jacobs Co., 491 F.3d 557, 564 (6th Cir.2007). This rule is premised on the rationale that “[i]t is grossly unfair to hold an employee accountable for acts which disqualify him from benefits if he had no knowledge of these acts or if these conditions were stated in a misleading or incomprehensible manner in the plan booklets.” Edwards, 851 F.2d at 136 (quotations and citation omitted). Thus, “[i]t is of no effect to publish and distribute a plan summary booklet designed to simplify and explain a voluminous and complex document and then proclaim that any inconsistencies will be governed by the plan.” Id. (quotations and citation omitted).
However, “[a]n omission from the summary plan description does not, by negative implication, alter the terms of the plan itself. The reason is obvious: by definition, a summary will not include every detail of the thing it summarizes.” Sprague v. Gen. Motors Corp., 133 F.3d 388, 401 (6th Cir.1998) (en banc) (citations omitted). Further, “under the law of this circuit, language in a plan summary that is merely ambiguous should not be permitted to trump unambiguous language in the plan itself[.]” Foltice v. Guardsman Prods., Inc., 98 F.3d 933, 938 (6th Cir. 1996); see also Lake v. Metropolitan Life Ins. Co., 73 F.3d 1372, 1379 (6th Cir.1996) (resolving ambiguity in summary plan description by referring to clarifying language in plan documents). Thus, while a conflict exists where the summary plan description misleads or fails to state additional requirements contained in the plan document, see Edwards, 851 F.2d at 136, there is no conflict where the plan document merely clarifies the summary’s general language, see Foltice, 98 F.3d at 938.
The LTD Benefit Booklet provides notice that to the extent that any conflict exists between its terms and the primary Plan documents, the primary Plan documents control. However, as this Court stated in Edwards, ERISA does not allow plan providers to short-cut their obligations to provide clear, comprehensive summary plan descriptions by including a conclusory warning in the summary that the more detailed plan document controls in case of conflict. Thus, regardless of the Plan’s disclaimers, to the extent that the provisions in the LTD Benefit Program contradict the LTD Benefit Booklet and mislead a Plan member, this Court must favor the terms in the LTD Benefit Booklet.
The LTD Benefit Booklet states that “[a] pre-existing condition is a sickness or injury for which you received medical care or services (including doctor visits, prescriptions and diagnostic tests) during the three months prior to your effective date of coverage.” (AR at 350.) The LTD *81Benefit Program defines “pre-existing condition” as “a sickness or injury for which you received treatment OR where symptoms were present to the degree that an ordinarily prudent person would seek treatment” during the three-month look-back period. (AR at 404.) The second part of the LTD Benefit Program’s definition, which focuses on whether symptoms of the disability were present during the look-back period, departs from the definition in the LTD Benefit Booklet. The LTD Benefit Booklet requires an employee to have received “medical care or services” for the disability, whereas the LTD Benefit Program could enable an employee to have a pre-existing condition even if the employee did not seek or receive any medical attention, but merely exhibited symptoms of a disease for which treatment begins after the effective date of coverage. We believe this distinction in the definitions is misleading, because nothing in the LTD Benefit Booklet would indicate that a doctor’s identification of symptoms of a subsequently diagnosed illness during the look-back period, by itself, could satisfy the definition of a pre-existing condition. Accordingly, we will not countenance the part of the LTD Benefit Program’s definition that refers to symptoms.2 However, because the remainder of the definition in the LTD Benefit Program appears to be a consistent elaboration of the definition in the LTD Benefit Booklet, this Court may consult it to the extent it clarifies any ambiguities in the LTD Benefit Booklet. See Foltice, 98 F.3d at 938.
IV.
Focusing on the definition of “pre-exist-ing condition” in the LTD Benefit Booklet,
the magistrate judge found ambiguity with respect to whether Mitzel’s treatment for the symptoms of WG during the three-month look-back period qualified her WG as a “pre-existing condition.” The magistrate judge then ruled for Mitzel by resolving the ambiguity against the Plan’s drafter pursuant to the doctrine of contra proferentem.
As an initial matter, we are troubled by the magistrate judge’s reliance on the rule of contra proferentem in this case. To be sure, this Court has invoked the rule in previous ERISA disputes, holding that “to the extent that the Plan’s language is susceptible of more than one interpretation, we will ... construe any ambiguities against ... the drafting parties.” Univ. Hosps. of Cleveland v. Emerson Elec. Co., 202 F.3d 839, 846-47 (6th Cir.2000); see also Perez v. Aetna Life Ins. Co., 150 F.3d 550, 557 n. 7 (6th Cir.1998) (en banc); Marquette Gen. Hosp. v. Goodman Forest Indus., 315 F.3d 629, 632 n. 1 (6th Cir. 2002).
However, in cases such as this one, in which the administrator’s denial of benefits is reviewed under the arbitrary and capricious standard because of the discretion conferred by the Plan, we believe that invoking the rule of contra proferentem undermines the arbitrary and capricious standard of review. Under the arbitrary and capricious standard, courts must favor a plan administrator’s interpretation over an equally reasonable contrary interpretation. See, e.g., Morgan v. SKF USA, Inc., 385 F.3d 989, 992 (6th Cir.2004) (“We must accept a plan administrator’s rational interpretation of a plan even in the face of *82an equally rational interpretation offered by the participants.”) (emphasis added). Moreover, although this Court appears to have applied the contra proferentem doctrine when reviewing under the arbitrary and capricious standard, see University Hospitals, 202 F.3d at 850, several circuits have held that the rule of contra proferen-tem does not apply where a plan bestows interpretative authority on its administrator. See Winters v. Costco Wholesale Corp., 49 F.3d 550, 554 (9th Cir.1995) (“We hold that the rule of contra proferentem is not applicable to self-funded ERISA plans that bestow explicit discretionary authority upon an administrator to determine eligibility for benefits or to construe the terms of the plan.”); Pagan v. NYNEX Pension Plan, 52 F.3d 438, 443 (2d Cir.1995) (“[Application of the rule of contra profer-entem is limited to those occasions in which this Court reviews an ERISA plan de novo.”); Lee v. Blue Cross/Blue Shield of Ala., 10 F.3d 1547, 1551 (11th Cir.1994) (noting, after citing cases from seven other circuits that invoked contra proferentem rule in ERISA context, that “all of the cited cases except [one] involve a de novo review of the challenged insurance plan”). Limiting the application of the contra prof-erentem rule to cases in which an administrator’s decision is reviewed de novo strikes us as the only sensible approach to resolving ambiguities in plan documents.
Regardless, the language of the LTD Benefit Booklet is unambiguous in supporting Mitzel’s argument that she did not have a pre-existing condition. “In interpreting a plan, the administrator must adhere to the plain meaning of its language as it would be construed by an ordinary person.” Morgan, 385 F.3d at 992. “In applying the ‘plain meaning’ analysis, we must give effect to the unambiguous terms of an ERISA plan.” Williams v. Int’l Paper Co., 227 F.3d 706, 711 (6th Cir.2000) (quotations and citations omitted).
The LTD Benefit Booklet states that a pre-existing condition is “a sickness or injury for which [Mitzel] received medical care or services.” (AR at 350.) (emphasis added). Although both documents go on to list some of the actions that would qualify as “treatment” or “medical care or services,” both constructions require the medical attention to be for the pre-existing condition. The Third Circuit, interpreting a similar “pre-existing condition” definition in a health care plan in the context of a contractual dispute, provided an analysis of the word “for” that this Court finds persuasive:
The word “for” connotes intent. Webster’s Dictionary states that “for” is “used as a function word to indicate purpose.” Webster’s Ninth New Collegiate Dictionary 481 (1986). Black’s Law Dictionary similarly states that the word “connotes the end with reference to which anything is, acts, serves, or is done. In consideration of which, in view of which, or with reference to which, anything is done or takes place.” Black’s Law Dictionary 579-80 (5th ed. 1979).... In short, it is hard to see how a doctor can provide treatment “for” a condition without knowing what that condition is or that it even exists.
Lawson ex rel. Lawson v. Fortis Ins. Co., 301 F.3d 159, 165 (3d Cir.2002); see also McLeod v. Hartford Life and Accident Ins. Co., 372 F.3d 618, 626 (3d Cir.2004) (“Finding the Lawson analysis persuasive, we construe the term ‘for’ to contain the Lawson element of intentionality [in the ERISA context].”)3 This Court has also *83previously opined in dicta that “the word ‘for’ can be read as connoting intent or purpose regarding the condition, such that treatment cannot be given ‘for’ a specific condition unless the nature of the condition is known.” LoCoco v. Medical Sav. Ins. Co., 530 F.3d 442, 447 (6th Cir.2008). We further noted in LoCoco that “in [ERISA] cases that dealt with clauses referring to conditions ‘for which’ treatment was provided ... courts have concluded that the ultimate condition need only have been suspected with a reasonable degree of likelihood in order to be considered ‘pre-exist-ing.’ ” Id. at 447-48 (emphasis added).4
The dissent quibbles with our use of the Third Circuit precedent, arguing without support from any case that, “the types of medical care or treatment specified by the Plan [do not] require that the doctor or the patient correctly diagnose or even suspect during the pre-existing period the actual sickness that is ultimately diagnosed.” Dissent at 85. The dissent continues to boldly assert how clear the Plan language is but supports its argument only with a dictionary definition of “sickness” and the aforementioned misleading dictionary definition of “for.” It relies on no additional language of the Plan and no case law. This lack of support is not surprising because the statement that a preexisting condition is “a sickness or injury for which you received treatment” in no way unambiguously encompasses treatments for symptoms of an undiagnosed illness. Given the dissent’s lack of cited authority, it appears no court in this country has read a similar clause the way that Judge McKeague finds is so clear. The much more logical reading is that the Plan requires some knowledge of what the sickness is in order to provide treatment for the sickness.
In denying Mitzel’s long-term disability claim, the only reference Anthem made to Mitzel receiving treatment was that Mitzel “consulted with Dr. Arsuaga” while displaying some of the symptoms of WG. (AR at 114.) However, Dr. Arsuaga stated that when he evaluated Mitzel during the look-back period, Mitzel did not meet the criteria for WG. Furthermore, nothing in the administrative record indicates that Dr. Arsuaga had even an inkling that Mitzel might have WG, let alone “suspected [WG] with a reasonable degree of likelihood,” see LoCoco, 530 F.3d at 447-48. Because none of Mitzel’s physicians even considered the possibility that she had WG before her effective date of coverage, none of *84them treated her for WG, notwithstanding the fact that she displayed some of the symptoms of that disease. It was unreasonable for Anthem to deny Mitzel’s claim simply because she presented symptoms associated with a later-diagnosed disease and consulted with a doctor during the look-back period in connection with those symptoms, where the doctor did not suspect, diagnose or treat the specific disability for which she eventually applied for benefits.5
Our reading of “pre-existing condition” in the LTD Benefit Booklet is supported by the part of the definition in LTD Benefit Program that we are free to consult. To reiterate, we find the entire explanation of “pre-existing condition” in the LTD Benefit Program consistent with the definition in the LTD Benefit Booklet, except for the phrase “a sickness or injury where symptoms were present to the degree that an ordinarily prudent person would seek treatment.” The non-conflicting part of the LTD Benefit Program’s definition states that a pre-existing condition is “a sickness or injuiy for which [Mitzel] received treatment.” (AR at 404) (emphasis added). The LTD Benefit Program lists a number of examples of “treatment,” but notably, does not includes medical attention for symptoms of a disease that is later diagnosed.
Because neither the definition of “preexisting condition” in the LTD Benefit Booklet nor the elaboration of the definition of “treatment” in the LTD Benefit Program includes a doctor’s consideration of symptoms which he was unable to connect to a subsequently diagnosed disease, Anthem’s denial of benefits based on this language was arbitrary and capricious. Accordingly, the district court was correct to reverse Anthem’s decision, even if resort to the rule of contra proferentem may not have been appropriate.
CONCLUSION
For the reasons set forth above, we AFFIRM the judgment of the district court.
. We note that the Plan documents themselves are far from clear as to which one is the summary document. The LTD Benefit Booklet contains a disclaimer that it is the summary document with respect to long-term disability benefits. However, the Summary Plan Description also states that it and the component programs listed in Exhibit C constitute both the Plan and the summary document. Compounding the confusion is the fact that both the Summary Plan Description and the LTD Benefit Booklet refer to themselves as the “Summary Plan Description" in some places. We fail to understand how these overlapping documents, each purporting to constitute a "summary” of the Plan, could possibly fulfill the mandate in § 1021(a)(1) to provide a clear, concise summary for Plan participants.
. Without commenting on this analysis or on the inconsistencies between the LTD Benefit Booklet and the LTD Benefit Program, the dissent refers to the "ordinarily prudent person” language. Not only is this reference misplaced for the reasons stated, but our analysis would remain unchanged since Mit-zel did seek treatment for her symptoms in any case.
. The dissent attempts to cite a dictionary as well for a definition of "for.” Its definition, meaning "because of,” is definition 8(a) in Webster’s Third New International Dictionary, Unabridged (2002). Counting subsections, Webster's lists twenty different definí-*83tions before the one relied on by the dissent. Furthermore, the example in the dictionary for the definition "because of” is "shouted for joy,” which is not at all how the term is used in the Plan. The same dictionary’s definition 3(c)(2) is "on the point of: having the intention of.” The dictionary's example is "was just for going to bed.” The language in the Plan more closely parallels the usage in this definition. The dissent's use of “because of” as the appropriate definition of "for” is not at all the "plain meaning of [the Plan’s] language as it would be construed by an ordinary person.” Morgan v. SKF USfA, Inc., 385 F.3d 989, 992 (6th Cir.2004).
. The dissent attempts to extend LoCoco far beyond what it actually holds. Judge McKeague cites LoCoco following his assertion that "a patient can have diagnostic tests for a sickness even though neither the patient nor the doctor suspected or correctly diagnosed the sickness at the time.” Dissent at 86. LoCoco dealt with a patient who was suspected of having lung cancer but who had not been officially diagnosed prior to coverage. It cites numerous cases where courts have emphasized that testing for a suspected but undiagnosed illness satisfy similar "for which” language. 530 F.3d at 447-48. Nothing in the case states that treatment for symptoms of an unknown illness are sufficient to satisfy "for which” language. If Mitzel's doctors had strongly suspected WG but had not received the results of diagnostic testing before coverage began, this would be a different case.
. Judge McKeague’s emphasis on the definition of "sickness” is somewhat confusing. Whether "sickness” standing alone requires a diagnosis is irrelevant where the Plan unambiguously requires that the treatment be for the sickness. In this case, the sickness is WG, and Mitzel received no treatment for WG during the look-back period when the treating physician had no idea that she suffered from that "sickness.”