Three Years Post-Bypass: When Prophylactic Vitamins Weren't Enough to Prevent This
A woman three years past Roux-en-Y gastric bypass presents with fatigue, neuropathy, and severe iron deficiency — deficiencies standard prophylactic supplementation should have prevented, raising an urgent repletion question and an honest adherence conversation.
Latoya M., a 44-year-old paralegal, is three years out from Roux-en-Y gastric bypass and has lost and kept off 110 pounds — a result she describes as having genuinely changed her life, which is part of why the tingling that's crept into both her feet over the past two months felt at first like something unrelated, easy to attribute to new shoes or standing too long at her desk. It wasn't until it started climbing past her ankles that she mentioned it to anyone, and by today's visit it's joined by a fatigue heavy enough that she's started leaving work early twice a week, something entirely out of character for her. Asked directly, rather than volunteering it, she added that she's been vomiting on and off for several weeks and had put it down to a stomach bug she couldn't shake — an aside in her telling, and the single detail that most changes how quickly the rest of this needs to move.
Her labs, drawn after that mention, tell a more urgent story than either symptom alone suggested: a ferritin of 8ng/mL, severely low, and a vitamin B12 at the low end of normal but trending down over her past two annual checks. Both deficiencies trace back to the same surgical anatomy — Roux-en-Y bypass reroutes food past the duodenum and proximal jejunum, the segment responsible for most dietary iron absorption and a meaningful share of the intrinsic-factor-cobalamin complex uptake that supports B12 status — but the severity of what's shown up on her labs is well beyond what standard post-surgical prophylactic multivitamin and supplement dosing is supposed to allow, which is itself a finding worth taking seriously alongside the numbers themselves.
In clinic, a deficiency severe enough to demand an honest conversation
Her fatigue and the peripheral neuropathy she's describing aren't just 'post-surgery tiredness' — I want thiamine checked and repleted before anything else today, even before the full micronutrient panel results are back. Roux-en-Y gastric bypass bypasses the duodenum and proximal jejunum, where thiamine absorption is concentrated, and prolonged vomiting on top of that malabsorption is exactly the combination that precedes Wernicke's encephalopathy — a preventable catastrophe if caught early and a permanent one if it isn't.
Agreed on the urgency, and I'd broaden the picture for a moment: her surgery bypassed the same duodenal segment responsible for the bulk of dietary iron absorption, which her ferritin of 8ng/mL confirms independently of anything today's exam is telling us. The ASMBS nutritional guidelines' standard post-RYGB prophylactic regimen should have covered this, and the fact that it didn't tells me her actual intake of the prescribed regimen, not just her surgical anatomy, needs a real, honest conversation.
I don't say that to blame her — adherence to a multi-pill daily regimen for years after surgery is genuinely hard, and it's a known, common gap in bariatric aftercare, not a personal failing specific to her.
That's the right framing, and it changes what I'd prescribe: oral iron repletion is unlikely to keep pace with a ferritin this low given her reduced absorptive surface, so I'd start IV iron rather than escalate an oral dose she may already be struggling to take consistently. Same logic for B12 — a monthly intramuscular injection removes the adherence variable entirely, rather than asking her to remember a daily oral dose on top of everything else in her regimen.
Agreed: give IV thiamine today ahead of any other intervention, start a scheduled IV iron infusion series rather than escalate an oral dose, and switch her B12 to monthly intramuscular injection to remove the daily-adherence variable entirely.
No real disagreement remained; both physicians approached the adherence conversation with Latoya directly and without judgment, and she acknowledged, once asked plainly, that she'd been taking her prescribed multivitamin only a few times a week rather than daily — information that changed the repletion plan from oral escalation to routes that don't depend on her remembering a pill.