Vitamin D optimization on GLP-1 — 12 month update

PharmHunterJen said:

I started taking a multivitamin as insurance and then found out that two of the things I was actually short of were the two it barely contains.

Iron studies on micronutrients — important especially for women:

My ferritin cratered at month 6 from reduced dietary intake. Iron bisglycinate 36mg with vitamin C brought it back up. Don't wait for anemia symptoms — test proactively.

TrialNerd_Beth said:

Iron studies on micronutrients — important especially for women: Marker Baseline Month 6 After Supplementation Ferritin 56 24 51 Iron 86 56 84 TIBC…

Vitamin D levels and micronutrients: an often-overlooked connection. Obese individuals store vitamin D in adipose tissue, making it less bioavailable. As you lose fat, vitamin D can actually increase WITHOUT supplementation.

My trajectory: Baseline 18 ng/mL → Month 6 (with supplement) 42 ng/mL → Month 12 48 ng/mL. Target is 40-60 ng/mL. Adequate vitamin D supports immune function, bone health, and mood — all relevant during weight loss.

PharmHunterJen said:

I started taking a multivitamin as insurance and then found out that two of the things I was actually short of were the two it barely contains.

Same experience, arrived at from the opposite direction. I had assumed I was the exception until I read this.

Adding the clinical framing, because it changes how the question reads.

Blood count monitoring for micronutrients: my doctor noticed my MCV (mean corpuscular volume) trending up at month 6: 91 → 97 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.