Vacated and remanded by published opinion. Judge SHEDD wrote the opinion in which Judge DIANA GRIBBON MOTZ joined. Judge WILLIAMS wrote a concurring opinion.
OPINION
SHEDD, Circuit Judge:In this ERISA appeal, we consider whether Metropolitan Life Insurance Company (MetLife) abused its discretion in denying the claim for long-term disability (LTD) benefits filed by Robert S. Evans. The district court granted summary judgment in favor of MetLife, finding that MetLife did not abuse its discretion. For the following reasons, we vacate the judgment of the district court and remand for further proceedings.
I.
Evans, a nuclear fuels engineer employed at BWX Technologies, Inc. (B & W), began experiencing abdominal pain and fatigue in February 1999. Evans first received treatment from his family physician, Dr. Kim Wright, but his abdominal pain persisted. Dr. Wright referred Evans to a gastroenterologist. Both Dr. Wright and the gastroenterologist diagnosed Evans as suffering from chronic abdominal pain and irritable bowel syndrome (IBS).
Despite his condition, Evans continued to work from February 1999 through December 1, 1999. Commencing December 2, 1999, Evans was given a week off from work. Dr. Wright thereafter continued Evans off work for more than six months. Evans’s childhood stuttering returned, so Dr. Wright referred him to a psychologist, Dr. Daniel Owens, for assessment in January 2000. Dr. Owens continued treating Evans through at least September 2000. While Evans was away from work, Dr. Wright also referred him to another gas-troenterologist at the University of Virginia for a second opinion. That doctor *309changed Evans’s medications, which provided some short-term relief.
Because Evans was feeling somewhat better, Dr. Wright thought it would be appropriate to return Evans to work at B & W on June 19, 2000. Dr. Wright hoped that once Evans returned to the routine of his job that his condition might continue to improve. Over the next six weeks, Evans worked sporadically; he worked some part-time days and some full-time days, but he also took off several sick days. His last day at work was July 27, 2000. Evans took several more leave days thereafter until August 9, 2000, when it appears B & W placed him on approved medical leave of absence.
B & W offers its employees LTD benefits through a group disability insurance policy (the Plan) issued by MetLife. Met-Life is also the administrator of the Plan. B & W filed the initial LTD application form with MetLife on behalf of Evans on August 9, 2000. On the form, B & W indicated that Evans’s “Date Last Worked” was December 1, 1999, but that his “Date Returned to Work” was June 19, 2000.
MetLife then contacted Evans, requesting that he submit several other forms and documentation. In response, Evans stated on his Disability Claim Employee Statement that his “Date Last Worked” was August 1, 2000, and that the “Date Disability Began” was December 2, 1999. He also explained that he was at that time suffering from almost constant abdominal pain, had frequent urges to use the restroom (often with less than 90 seconds’ warning), spent from two to six hours every day in the restroom, and was generally mentally exhausted.
Evans also submitted Attending Physician Statements from some of his treating doctors. The first gastroenterologist indicated that he had treated Evans for IBS but had last seen him on June 15, 2000 — a few days before Evans returned to work.1 Dr. Wright stated that Evans was suffering from IBS. She also indicated that she had discussed with Evans before August 2000 the possibility that he might be disabled from performing his job but that she definitely advised Evans to cease his job as .of August 8, 2000. Dr. Owens indicated that he advised Evans to cease his job as of July 27, 2000.
MetLife denied Evans’s claim for disability, concluding that there was no evidence supporting his claimed inability to perform his job. MetLife also concluded there was no medical documentation establishing that Evans was suffering from IBS.
Evans hired a lawyer to appeal Met-Life’s denial. The lawyer wrote a lengthy letter outlining the purported errors made by MetLife in its review. The lawyer also submitted letters from Dr. Wright and Dr. Owens further explaining their opinions that Evans became disabled on about his last day at work — July 27, 2000. The lawyer also submitted a copy of the Social Security Administration’s award of disability benefits to Evans effective December 2, 1999. The lawyer insisted that the evidence showed that Evans was disabled as of December 2, 1999.
MetLife reviewed this new documentation, but affirmed its original denial of Evans’s LTD claim. MetLife stated that *310Evans’s last day of work was December 1, 1999 — not July 27, 2000 as the record clearly reflects — and that there was no evidence to support a disabling impairment as of December 1, 1999. In support of this finding, MetLife relied in part on the opinions of Drs. Wright and Owens that Evans did not become disabled until on or about August 1, 2000.
Evans then filed this ERISA lawsuit against MetLife, seeking to recover benefits under the Plan. MetLife moved for summary judgment, arguing that it properly exercised its discretion in deciding that Evans had failed to establish that he was totally disabled “when he quit work on December 1, 1999.” J.A. 42. In his written response, Evans argued, in effect, that MetLife failed to give adequate weight to the evidence Evans submitted. Evans did not expressly argue in his brief that Met-Life should have determined whether he was disabled as of August 2000 rather than as of December 2, 1999.
The district court held a hearing on MetLife’s motion for summary judgment. During the hearing, MetLife contended that it was Evans’s burden, pursuant to the Plan requirements, to show that he was totally disabled from the time he quit work — December 2, 1999 — and thereafter through a six-month “Elimination Period.” Although MetLife has never stated a specific date, this “Elimination Period” would have expired, based on MetLife’s interpretation of the Plan, on June 2, 2000, before Evans returned to work on June 19, 2000.
Evans countered, for the first time before the district court, that the disability determination should have been made as of August 2000, after Evans returned to work. In reply, MetLife conceded that there was some medical evidence in the record that Evans was disabled as of August 2000, but MetLife insisted that the proper date to determine disability was as of December 2, 1999 and during the subsequent six-month “Elimination Period.”
The district court granted summary judgment in favor of MetLife, ruling that MetLife’s decision to deny benefits resulted from a reasoned, disciplined, deliberative process. The district court did not, however, indicate whether the proper date to determine disability was as of December 2, 1999 or August 2000.2
Evans now appeals, arguing that Met-Life’s use of December 1999 as the date to determine disability contravenes the terms of the Plan. He contends that MetLife abused its discretion by ignoring evidence that he was totally disabled as of August 2000.3
II.
When an ERISA plaintiff appeals a grant of summary judgment, we conduct a de novo review, applying the same standards that the district court employed. Ellis v. Metropolitan Life Ins. Co., 126 F.3d 228, 232 (4th Cir.1997). In cases in which the ERISA benefit plan gives the administrator of the plan discretion to determine eligibility for benefits, we review a denial of benefits by the administrator for abuse of discretion. Id. at 232. Under this deferential standard, we will not disturb the administrator’s decision if it is *311reasonable, even if we would have come to a different conclusion independently. Booth v. Wal-Mart Stores, Inc., 201 F.3d 335, 341 (4th Cir.2000). Such a decision is reasonable if it is the result of a deliberate and principled reasoning process and is supported by substantial evidence. Brogan v. Holland, 105 F.3d 158, 161 (4th Cir.1997).
In this case, it is undisputed that the Plan gives MetLife discretionary authority to determine entitlement to Plan benefits. Thus, we review MetLife’s denial of Evans’s claim for benefits for an abuse of discretion. However, because MetLife is both administrator of the Plan and its insurer, a conflict of interest exists, and that conflict must be weighed as a factor in determining whether an abuse of discretion occurred. See Ellis, 126 F.3d at 233.4
III.
MetLife insists that Evans could not recover benefits unless he proved that “he was totally disabled when he quit work in December 1999 and continuously through the six-month Elimination Period.” MetLife Brief, p. 22. MetLife claims that Evans failed to produce any evidence that he was disabled during this particular period — December 2, 1999 through June 2, 2000. MetLife relies in part on the opinions of Dr. Wright and Dr. Owens — that Evans should have ceased work no earlier than July 27, 2000 — to suggest that Evans was not disabled from December 2, 1999 through June 2, 2000.
We do not agree that Evans was necessarily required to prove that he was disabled from December 2, 1999 through June 2, 2000. First, Evans did not “quit work” on December 2, 1999. Although Evans did not work from December 2, 1999 through June 19, 2000, the undisputed evidence in the record is that Evans remained an employee of B & W until at least August 2000. He actively worked more than ten days between June 19 and July 27, 2000 and was subsequently allowed to take several leave days through August 8, 2000.
Second, MetLife has failed to cite any provision in the Plan that would necessarily start the disability determination date as of the date Evans “quit work.”5 To the contrary, the Plan provides:
When we [MetLife] receive proof that you are Totally Disabled, we will pay a Monthly Benefit in accordance with the SCHEDULE OF BENEFITS.
J.A. 74. Under this provision, the clock for determining disability under the Plan starts whenever MetLife receives sufficient proof that an eligible participant becomes totally disabled. Based on this provision, MetLife is free to deny benefits once it decides — based on a deliberate, principled review of the evidence it receives — that the participant has failed to produce sufficient proof that he is totally disabled. However, what MetLife may not do under this provision is to base its determination of disability as of a particular date if the evidence submitted establishes another date that the disability may have begun.6 MetLife is obligated under the *312Plan to consider all the evidence it receives and must pay monthly benefits if it receives proof that the eligible participant7 is totally disabled.8
It is clear in this case that MetLife improperly refused to consider whether the evidence it received established that Evans was disabled as of August 2000. MetLife candidly admitted to the district court that there was some evidence that Evans was disabled as of August 2000, but it argued that this evidence was immaterial because the proper determination date was December 2, 1999, the date Evans originally claimed he became disabled. In fact, there is absolutely no evidence in the record that MetLife considered any date other than December 2 as an acceptable date to consider whether Evans’s disability began. MetLife, in effect, ignored the evidence that Evans may have been disabled as of August 2000. Because MetLife refused to consider the evidence and the claim as of August 2000, we conclude that MetLife abused its discretion. See James v. Jacobson, 6 F.3d 233, 239 (4th Cir.1993)(stating that “failure or refusal, either express or implicit, actually to exercise discretion” constitutes an abuse of discretion).
IV.
Because MetLife abused its discretion by failing to consider whether Evans was disabled as of August 2000, we vacate the judgment of the district court and direct the district court to remand this case for further administrative review by MetLife consistent with this opinion.
VACATED AND REMANDED
. The gastroenterologist did not respond to all the questions on the form. In particular, he did not state whether he advised Evans to cease work. MetLife attempts to draw the inference from this omission that the gas-troenterologist did not believe that Evans was disabled. We disagree. The fact that the gastroenterologist did not answer the question one way or the other means that no inference can be drawn from the nonres-ponse.
. The district court can hardly be criticized for not focusing on whether December 1999 or August 2000 was the proper disability determination date. Evans failed to argue that August 2000 was the proper date until oral argument on the motion for summary judgment and did so only modestly. Nevertheless, the argument was made to the district court, and it is preserved for our review on appeal.
. Evans advances other arguments, but we need not reach them since we are remanding the case for further administrative review.
.At oral argument on appeal, Evans argued for the first time that the district court should have employed the less deferential de novo standard of review rather than abuse of discretion. We deem this argument abandoned on appeal. See Edwards v. City of Goldsboro, 178 F.3d 231, 241 n. 6 (4th Cir.1999).
. "Quit work" is not a term used in, or defined by, the Plan.
. We are aware that Evans stated in his initial form seeking benefits that his disability began on December 2, 1999, and that his lawyer, relying in part on the award of benefits by Social Security, also represented during the *312administrative appeal that Evans's disability commenced December 2, 1999. Nevertheless, MetLife was not allowed, under the Plan, to necessarily limit its disability determination to the date claimed by Evans and his lawyer. The Plan requires MetLife to review all evidence it receives to determine disability. MetLife admittedly had evidence before it throughout its administrative review that Evans's alleged disability may have begun after his last day of work, July 27, 2000.
. Throughout this entire case, MetLife has never argued that Evans is not an eligible participant under the Plan. Now, for the first time, the concurrence suggests, based on policy language not raised by MetLife, that Met-Life should have first determined whether Evans was an eligible participant under the Plan as of August 2000. We do not confront this issue because it is not before us. Our review is to determine whether MetLife abused its discretion in the actions it took — and its stated justifications — in denying benefits to Evans.
. MetLife asserts that the "Elimination Period” began on December 2, 1999, the date Evans originally claimed he became disabled. MetLife's interpretation of when the "Elimination Period” began is also incorrect.
According to the Plan, the "Elimination Period” is the "number of consecutive days [at least six months] of Total Disability before Long Term Disability. Benefits become payable,” and it commences "on the first day of Total Disability." J.A. 73. Thus, the "Elimination Period” begins when MetLife determines that it has received sufficient proof that a participant is totally disabled. MetLife would then become obligated to pay monthly benefits, starting when the "Elimination Period” expires — at least six months later. Obviously, if MetLife determines that a participant is not totally disabled, the "Elimination Period” never commences.
In this case, MetLife decided that Evans was not totally disabled, so the "Elimination Period” never started. If, however, MetLife were to decide on remand that Evans became totally disabled as of August 2000, the "Elimination Period” would have started in August 2000, and MetLife's obligation to pay monthly benefits would not have commenced before February 2001 — at least six months later.