Vitamin B12 monitoring — deficiency prevalence on GLP-1 therapy

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.

Vitamin and mineral labs to check while on micronutrients — my doctor orders these quarterly:

• B12: Can drop due to reduced GI absorption. Mine went from 650 to 380 — now supplementing.
• Iron/Ferritin: Reduced food intake = reduced iron. Ferritin dropped from 70 to 27. Supplementing.
• Vitamin D: Was already low (21 ng/mL), now taking 5000 IU daily.
• Folate: Stable, no issues.
• Zinc: Slightly low, added a multivitamin with zinc.

Nutritional deficiencies are a real risk when you're eating significantly less. Don't skip your labs!

Following on from LipidDoc_ATL — and this may be the naive question:

How people separated a drug effect from the ordinary consequences of a large deficit and disrupted sleep, because I cannot?

jason_paloalto said:

Vitamin and mineral labs to check while on micronutrients — my doctor orders these quarterly: B12: Can drop due to reduced GI absorption.

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.

Closing the loop on my own question.

Update: I got the sleep and the intake sorted before deciding it was the drug, and most of the flatness went with them. Not all of it, and I am watching the rest.

Dr.PainCLE said:

Iron studies on micronutrients — important especially for women: Marker Baseline Month 6 After Supplementation Ferritin 60 18 45 Iron 90 50 88 TIBC…

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