Supplement safety
Most supplements are safe at the stated dose for healthy adults.
Short answer Most supplements are safe at the stated dose for healthy adults. Problems come from high doses, stacking products with the same nutrients, and interactions with medicines.
Nutrients to keep an eye on
| Nutrient | Take care above |
|---|---|
| Vitamin A | 1.5mg a day; avoid supplements in pregnancy |
| Vitamin D | 100 micrograms a day |
| Vitamin B6 | 10mg a day long term |
| Iron | 17mg a day unless prescribed |
| Magnesium | 400mg a day from supplements |
| Vitamin C | 1,000mg a day |
Common interactions
Vitamin K and warfarin; St John's wort and many medicines including the pill; calcium, iron and magnesium with some antibiotics and thyroid tablets; fish oil at high doses with blood thinners. A pharmacist can check yours in a minute.
Who should always ask first
Anyone pregnant or breastfeeding, children, people with kidney or liver disease, and anyone before surgery.
Related pages
- How to choose a supplementAsk six things: do I need it, is the dose sensible, is the form one I will take, does it have evidence, is it safe for me, and what does it cost per day?.
- Pregnancy vitamins and supplementsUK advice is to take 400 micrograms of folic acid daily from before conception until 12 weeks, and 10 micrograms of vitamin D daily throughout pregnancy.
- Vitamins and mineralsMost people can get the vitamins and minerals they need from a varied diet.
Keep exploring
- Whey protein
- Melatonin
- Multivitamins
- Wellosophy Natural Balance Shake
- Collagen and menopause
- Probiotics for women
Questions people ask
Can supplements be harmful?
Yes, at high doses or in combination with some medicines.
Can I take this with medication?
Ask a pharmacist or GP first; some supplements interact with medicines.
Do supplements replace a balanced diet?
No. They are meant to add to a varied diet, not stand in for one.
Sources
- NHS: Vitamins and minerals (opens in a new tab)
- NHS: Vitamin D (opens in a new tab)
- NHS: Iron (opens in a new tab)
Checked 9 October 2026.