7 Vitamins Most Likely to Drop on GLP-1

When GLP-1 medications reduce your caloric intake by 30-50%, you are not just eating fewer calories, you are consuming fewer vitamins and minerals. Reduced stomach acid production and altered GI function can further impair nutrient absorption. These seven vitamins and minerals are the most likely to become deficient during GLP-1 treatment, and proactive supplementation can prevent problems before they start.

1. Vitamin B12

Risk level: High. GLP-1 reduces stomach acid needed for B12 absorption, and lower food intake decreases dietary sources. Deficiency causes fatigue, neurological symptoms (numbness, tingling), and cognitive changes that can become irreversible.

Recommendation: 1,000 mcg methylcobalamin daily, sublingual preferred.

2. Vitamin D

Risk level: High. Already deficient in many obese individuals. Reduced fat-soluble vitamin absorption and decreased dietary intake compound the problem. Essential for bone health, muscle function, and immune regulation.

Recommendation: 2,000-4,000 IU vitamin D3 daily. Take with a meal containing fat.

3. Iron

Risk level: Moderate to high (especially in menstruating women). Reduced meat consumption and altered stomach acid affect iron intake and absorption. Causes fatigue, weakness, and exercise intolerance.

Recommendation: Monitor ferritin levels. Supplement if ferritin drops below 30 ng/mL. Take iron with vitamin C for absorption.

4. Calcium

Risk level: Moderate. Reduced dairy intake decreases dietary calcium. Weight loss itself increases bone turnover. Combined with vitamin D deficiency, this creates bone health risk.

Recommendation: 500-1,000 mg calcium daily, split into two doses. Calcium citrate is preferred (better absorbed with reduced stomach acid).

5. Magnesium

Risk level: Moderate. Already one of the most common deficiencies in the general population. Reduced food intake decreases magnesium sources. Deficiency causes muscle cramps, sleep disturbance, and constipation (which GLP-1 already promotes).

Recommendation: 200-400 mg magnesium citrate or glycinate daily. Citrate form has the added benefit of promoting bowel regularity.

6. Zinc

Risk level: Moderate. Found primarily in meat, shellfish, and legumes. Reduced food intake decreases zinc consumption. Zinc deficiency impairs immune function, wound healing, taste sensation, and hair health.

Recommendation: 15-30 mg zinc daily. Often included in quality multivitamins. Take with food to prevent nausea.

7. Folate (Vitamin B9)

Risk level: Moderate. Found in leafy greens, legumes, and fortified grains. Eating less overall means less folate. Essential for cell division, DNA synthesis, and particularly important for women of childbearing age.

Recommendation: 400-800 mcg methylfolate daily. Included in most quality multivitamins.

The Practical Supplement Stack for GLP-1

Rather than taking seven separate supplements, most GLP-1 patients can cover their bases with:

1. High-quality multivitamin: Covers folate, zinc, and baseline amounts of other vitamins
2. Vitamin D3: 2,000-4,000 IU daily (multivitamins usually do not contain enough)
3. Vitamin B12: 1,000 mcg sublingual methylcobalamin
4. Magnesium citrate: 200-400 mg daily (helps with constipation too)
5. Calcium citrate: 500 mg daily if dairy intake is low
6. Iron: Only if lab work shows deficiency (do not supplement iron without testing)

Monitoring Schedule

• Baseline: Comprehensive metabolic panel, B12, vitamin D, ferritin, CBC
• 6 months: Recheck B12, vitamin D, ferritin
• 12 months: Comprehensive reassessment
• As symptoms arise: Fatigue, numbness, hair loss, muscle cramps, or other deficiency symptoms

Getting Started

Nutritional monitoring is part of quality GLP-1 care. Visit Trimi's treatment options page. Compounded semaglutide is $99/month and tirzepatide is $125/month.

Frequently Asked Questions

Do I need supplements on GLP-1?

Most GLP-1 patients benefit from basic supplementation because reduced caloric intake makes it difficult to meet all vitamin and mineral needs through diet alone. At minimum, consider a multivitamin, vitamin D, and B12.

Can I just take a multivitamin?

A quality multivitamin covers many bases but typically does not contain enough vitamin D, B12, or magnesium to meet GLP-1 patients' needs. Supplement these individually in addition to a multivitamin.

When should I take supplements on GLP-1?

Take fat-soluble vitamins (D, calcium) with meals containing some fat. Take B12 sublingual any time. Take iron separately from calcium and coffee. Magnesium can be taken before bed to support sleep and bowel regularity.