Vitamin, mineral and supplement guides
Plain guides to 44 vitamins, minerals and popular supplements: what each does, how much adults need, the upper limit in the US and the UK, and answers to 43 common dose questions. Every figure comes from the NIH Office of Dietary Supplements, NCCIH, the FDA and NHS guidance.
General information, not medical advice. Check with a doctor or pharmacist before taking a supplement, especially if you are pregnant or breastfeeding, take any medicine, or are under 18.
Is this dose too much?
- Is 5000 IU of vitamin D too much?
- Is 10,000 IU of vitamin D safe?
- Is 2000 IU of vitamin D a day safe?
- Is 1000 IU of vitamin D a day safe?
- Is 500 mg of magnesium too much?
- Is 400 mg of magnesium too much?
- Is 500 mg of magnesium glycinate too much?
- Is 10 mg of melatonin too much?
- Is 400 mg of caffeine a day too much?
- Is 200 mg of caffeine a day too much?
- Is 1000 mg of vitamin C too much?
- Is 2000 mg of vitamin C too much?
- Is 50 mg of zinc too much?
- Is 25 mg of zinc a day safe?
- Is 5000 mcg of biotin safe?
- Is 10,000 mcg of biotin too much?
- Is 1000 mcg of B12 too much?
- Is 5000 mcg of B12 too much?
- Is 65 mg of iron too much?
- Is 18 mg of iron a day safe?
- How much fish oil is too much? Is 3000 mg a day OK?
- Is 1000 mg of fish oil a day safe?
- Is 5 g of creatine a day safe?
- Is 10 g of creatine a day too much?
- Is 1200 mg of calcium too much?
- Is 100 mg of vitamin B6 too much?
- Is 50 mg of vitamin B6 safe?
- Is 10,000 IU of vitamin A too much?
- Is 1000 IU of vitamin E too much?
- Is 400 IU of vitamin E safe?
- Is 1000 mcg of folic acid too much?
- Is 500 mg of niacin too much?
- Is 200 mcg of selenium too much?
- Is 1000 mcg of iodine too much?
- Is a 99 mg potassium supplement safe?
- Is 600 mg of ashwagandha too much?
- Is 1000 mg of turmeric a day too much?
- Is 200 mg of L-theanine too much?
- Is 1500 mg of berberine a day too much?
- Is 10 g of collagen a day too much?
- Is 200 mg of CoQ10 too much?
- Is 200 mcg of vitamin K2 too much?
- Is 2 mg of copper a day safe?
Vitamins
- Vitamin A
- Thiamin (vitamin B1)
- Riboflavin (vitamin B2)
- Niacin (vitamin B3)
- Pantothenic acid (vitamin B5)
- Vitamin B6
- Biotin (vitamin B7)
- Folate (vitamin B9)
- Vitamin B12
- Vitamin C
- Vitamin D
- Vitamin E
- Vitamin K
- Choline
Minerals
Omega-3 and popular supplements
- Omega-3 and fish oil (EPA and DHA)
- Creatine
- Melatonin
- Caffeine
- Ashwagandha
- Turmeric (curcumin)
- Probiotics
- Collagen
- CoQ10 (coenzyme Q10)
- Protein powder
- Glucosamine and chondroitin
- Elderberry
- St John's wort
- L-theanine
- Berberine
- Psyllium fibre
- Green tea extract
Ask Supplement Check yourself
Add up everything you take, or paste a product name, and see the daily totals against the adult limits. Open Supplement Check, free, no sign-up.
In Claude or any app that takes MCP connectors, add https://goodturn-mcp.pages.dev/supplementcheck/mcp and ask: “I take a multivitamin, vitamin D 5000 IU and zinc 50 mg. Is that too much?”