Micronutrient deficiency risk on GLP-1 — B12, D, iron, zinc, folate

B12Beth said:

A sustained drop to 1,100 or 1,200 calories reliably under-delivers a predictable set: B12, vitamin D, iron, folate, zinc and magnesium.

Blood count monitoring for micronutrients: my doctor noticed my MCV (mean corpuscular volume) trending up at month 6: 89 → 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.

A narrower follow-up, since the general answer is now clear:

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

Dr.GutHealth said:

Blood count monitoring for micronutrients: my doctor noticed my MCV (mean corpuscular volume) trending up at month 6: 89 → 98 fL.

Coming at Dr.GutHealth’s question from a different direction. It is worth asking what the claim would look like if it were false. If nothing would look different, it is not a claim about the world and no amount of discussion will settle it.

If somebody has the primary source to hand I would rather cite it than paraphrase it.

Reporting back.

Update — I was wrong in the opening post, specifically about the direction. Correcting it here rather than editing it away.

PharmHunterJen said:

It is worth asking what the claim would look like if it were false.

True, with the qualification that this is a self-selected group. The people for whom it did not work post less, and that shapes everything we think we know.

Ask again with the specifics and you will get a better answer than this one.