There's no vitamin you're required to take with Ozempic. The 2025 joint advisory on nutrition for GLP-1 therapy says vitamin D, calcium and vitamin B12 can be considered for people at risk, and a basic multivitamin-mineral can fill gaps when you're eating very little.
The bigger gap for most people is protein: about 80-120 g a day. Get blood work, then let the results decide the doses. Talk to your prescriber before you add anything.
Key takeaways
- Protein first: the advisory suggests 1.2-1.6 g per kg of body weight a day during active weight loss, or a simple 80-120 g.
- A multivitamin is a fair safety net if you eat under about 1,200 calories (women) or 1,800 (men).
- Vitamin D: the RDA is 600 IU a day to age 70 and 800 IU after. The upper limit is 4,000 IU.
- Test before you take iron. Too much is harmful, and many people don't need it.
- Skip weight-loss and stimulant supplements. They add risk and nothing the medication isn't already doing.
Why Ozempic can leave nutrient gaps
Semaglutide (Ozempic, Wegovy) cuts appetite and slows stomach emptying. The joint advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association and The Obesity Society reports that GLP-1 drugs lower energy intake by 16-39%.
Eating that much less makes it harder to cover every nutrient. The advisory flags the risk as highest below about 1,200 calories a day for women and 1,800 for men, and lists these nutrients of concern: iron, calcium, magnesium, zinc, and vitamins A, D, E, K, B1, B12 and C.
Side effects add to it. Nausea can push protein-rich foods off the plate, and vomiting or diarrhea can lead to dehydration. The FDA label notes kidney injury has been reported in people who got dehydrated from these side effects, so fluids matter as much as any pill.
Vitamins and supplements to consider on Ozempic
Adult daily amounts below are the Recommended Dietary Allowances (RDAs), not treatment doses. If a blood test shows a deficiency, your doctor may prescribe more.
| Supplement | Why it comes up on Ozempic | Adult daily amount (RDA) | Notes |
|---|---|---|---|
| Protein (food, shakes) | Lean mass loss during fast weight loss | 80-120 g, or 1.2-1.6 g/kg | Food first; shakes when appetite is low |
| Multivitamin-mineral | Low total food intake | About 100% of daily values | A safety net, not a fix for a deficiency |
| Vitamin D | Named in the 2025 advisory | 600 IU (15 mcg) to age 70; 800 IU (20 mcg) after | Upper limit 4,000 IU (100 mcg) |
| Calcium | Named in the 2025 advisory; bone health | 1,000-1,200 mg for most adults | Count dairy and fortified foods first |
| Vitamin B12 | Named in the 2025 advisory | 2.4 mcg | Test if you take metformin or eat little animal food |
| Iron | Nutrient of concern | 18 mg women 19-50; 8 mg men and women 51+ | Only if a test shows you need it |
| Magnesium | Nutrient of concern | 310-320 mg women; 400-420 mg men | Food first; magnesium laxatives count too |
Protein
Protein isn't a vitamin, but it's the gap that matters most. In the STEP 1 trial of semaglutide 2.4 mg (the Wegovy dose), about 38% of the weight people lost was lean mass (5.3 kg of 13.6 kg), and the advisory's authors estimate about half of that was muscle.
The advisory suggests 1.2-1.6 g of protein per kg of body weight a day while you're actively losing weight, or a simpler fixed target of 80-120 g. It also says shakes, bars and fortified foods are a fair way to close the gap. See how much protein you need on Ozempic for the full breakdown, or get a number from the protein calculator.
Multivitamin-mineral
A standard multivitamin at roughly 100% of daily values is the simplest way to cover the long list of nutrients of concern. It won't correct a real deficiency, and it isn't needed if you still eat a varied diet at a moderate intake. Avoid "mega-dose" formulas unless a doctor prescribes them.
Vitamin D and calcium
The advisory names both. The Institute of Medicine set the vitamin D RDA at 600 IU (15 mcg) a day for ages 1-70 and 800 IU (20 mcg) for 71 and older, and found that higher blood levels weren't consistently better. The upper limit for adults is 4,000 IU.
Get calcium from dairy, fortified plant milk, tofu set with calcium and canned fish with bones first, then supplement the difference if you fall short.
Vitamin B12
Adults need 2.4 mcg a day. If you still eat fish, meat, eggs or dairy, or take a multivitamin, you're likely covered. Ask for a test if you also take metformin, which is linked to lower B12, or if you eat few animal foods. Tingling, numbness and unusual fatigue are worth mentioning to your doctor.
Iron
The RDA is 18 mg a day for women 19-50 and 8 mg for men and for women over 50. Iron supplements can cause constipation, which is already a common Ozempic side effect, and excess iron is harmful. Take iron only if a ferritin or iron test says you need it, and ask your pharmacist how to time it around calcium and your other supplements.
Magnesium
Adult RDAs are 310-320 mg for women and 400-420 mg for men. Nuts, seeds, beans and whole grains are the best food sources. If you use a magnesium-based laxative for constipation, count it, since supplements and laxatives are where excess magnesium usually comes from.
Fiber
Constipation is one of the most common side effects. The advisory recommends fluids and gradually more fiber from food. Our guide to Ozempic constipation and fiber covers which foods help. Ask your prescriber before adding a fiber supplement.
Creatine and omega-3
Neither has been tested much in GLP-1 users specifically. Creatine monohydrate at 3-5 g a day is the standard dose in the International Society of Sports Nutrition position stand, and it pairs with strength training, not instead of it. Fish twice a week is a simpler way to get omega-3s than a capsule.
Supplements to skip or ask about first
- Weight-loss supplements and fat burners. They add risk and duplicate what the medication already does.
- Stimulant pre-workouts and high-caffeine products. They can make nausea and a racing heart worse.
- High-dose single nutrients without a test, especially iron and preformed vitamin A.
- Anything you haven't told your prescriber about. Semaglutide slows stomach emptying, and the label warns it may affect how oral medicines are absorbed. The patient information asks you to list all vitamins and herbal supplements.
Blood tests to ask your doctor about
A baseline panel lets you supplement what you're actually low in instead of guessing. Common tests to ask about:
- Vitamin D (25-hydroxyvitamin D)
- Vitamin B12
- Complete blood count and ferritin (iron stores)
- Basic or comprehensive metabolic panel (kidney function, potassium, sodium)
- Magnesium
- HbA1c and fasting glucose
Repeat tests are worth discussing after several months of fast weight loss or if you're eating far less than before. For what each deficiency looks like, see GLP-1 nutrient deficiencies.
Does Ozempic cause hair loss?
Hair shedding can follow any fast weight loss, with or without medication. No supplement has been shown to prevent it in GLP-1 users. Low protein, iron or zinc can make shedding worse, which is one more reason to test instead of taking high doses of "hair" supplements. Hitting your protein target is the most useful step you control.
Track what you actually eat
Supplements only fill gaps you can see. Because appetite drops so much, many people on Ozempic don't realize how little protein they're getting until they log a few days.
Nutrify lets you log meals from a photo or a quick search and shows your protein against your target each day. It has a 7-day free trial, then a paid subscription. For meal ideas built around protein, see what to eat on Ozempic and our list of high-protein foods for GLP-1 users.
Sources
- Mozaffarian D, et al. Nutritional priorities to support GLP-1 therapy for obesity: a joint advisory from the ACLM, ASN, OMA and TOS. Obesity, 2025.
- Ross AC, et al. The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine. J Clin Endocrinol Metab, 2011.
- MedlinePlus (US National Library of Medicine): vitamin D, calcium, vitamin B12, B12 deficiency and metformin, iron, iron supplements, magnesium.
- Kreider RB, et al. ISSN position stand: safety and efficacy of creatine supplementation. J Int Soc Sports Nutr, 2017.
- US FDA, Wegovy (semaglutide) prescribing information and patient information, FDALabel.
