laura_annarbor said:

Six months of eating roughly 1,100 calories a day and my ferritin has halved, which I did not connect to the intake until somebody pointed it out.

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 64 to 31. Supplementing.
• Vitamin D: Was already low (23 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!

Dr.KarenChen 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.

laura_annarbor said:

Six months of eating roughly 1,100 calories a day and my ferritin has halved, which I did not connect to the intake until somebody pointed it out.

This is my experience too, for whatever a second data point is worth.

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

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.