Iron deficiency on GLP-1 — May 2025

anders_CPH said:

Vitamin D levels and micronutrients: an often-overlooked connection.

Blood count monitoring for micronutrients: my doctor noticed my MCV (mean corpuscular volume) trending up at month 6: 91 → 98 fL. This flagged potential B12 or folate deficiency.

Sure enough, B12 had dropped from 620 to 340 pg/mL. Started B12 injections monthly and MCV normalized within 2 months. GLP-1 agonists can impair B12 absorption — this is a real clinical concern that deserves routine monitoring.

The figures, for anyone assembling their own picture. The boring version of this is the one that works, and the boring version is: measure a baseline, change one variable, wait, measure again under the same conditions. Nobody wants that answer and it is still the answer.

BenResearch_OR said:

Blood count monitoring for micronutrients: my doctor noticed my MCV (mean corpuscular volume) trending up at month 6: 91 → 98 fL.

Adding the part of the answer the thread has not reached. Worth answering the question that was asked rather than the one behind it. The narrow version usually has an answer; the broad version usually does not, and answering the broad one is how a thread stops being useful.

One thing that is still open after Dr.SurgeonPGH’s answer:

Did your prescriber agree with that reading, and if not what was their objection?

Closing the loop on my own question.

Update, and it is the boring outcome: nothing was wrong. The measurement I was reading had moved less than its own week-to-week variation, which somebody said upthread and I did not believe.