Safety tool
Upper safe limit checker
Pick a nutrient and enter the daily amount you take from supplements to see it against the NHS or EFSA tolerable upper intake guidance, the daily amount above which the safety margin narrows. If you take several products, add up the same nutrient across all of them first, because the total is what matters. Information only, not medical advice; speak to your GP or pharmacist.
Reference table
| Nutrient | Upper guidance | Basis and source |
|---|---|---|
| Vitamin D | 100 mcg/day | NHS: do not take more than 100 mcg (4,000 IU) a day unless advised by a clinician. NHS, Vitamin D. |
| Vitamin C | 1000 mg/day | NHS: taking 1,000 mg or less a day of vitamin C supplements is unlikely to cause harm. NHS, Vitamin C. |
| Vitamin B6 (pyridoxine) | 10 mg/day | NHS: taking 10 mg or less a day of vitamin B6 supplements is unlikely to cause harm; long-term high doses can cause nerve problems. NHS, B vitamins and folic acid. |
| Folic acid | 1000 mcg/day | NHS: taking 1,000 mcg or less a day of folic acid supplements is unlikely to cause harm. NHS, B vitamins and folic acid. |
| Magnesium (supplements) | 400 mg/day | NHS: taking 400 mg or less a day of magnesium in supplements is unlikely to cause harm (this is the supplemental figure, not total diet). NHS, Others: vitamins and minerals. |
| Iron (supplements) | 17 mg/day | NHS: taking 17 mg or less a day of iron supplements is unlikely to cause harm; higher doses only under medical advice. NHS, Iron. |
| Zinc | 25 mg/day | NHS: taking 25 mg or less a day of zinc supplements is unlikely to cause harm. NHS, Others: vitamins and minerals (zinc). |
| Selenium | 350 mcg/day | NHS: taking 350 mcg or less a day of selenium supplements is unlikely to cause harm. NHS, Others: vitamins and minerals (selenium). |
| Calcium | 1500 mg/day | NHS: taking 1,500 mg or less a day of calcium supplements is unlikely to cause harm. NHS, Calcium. |
| Iodine | 500 mcg/day | NHS: taking 500 mcg or less a day of iodine supplements is unlikely to cause harm. NHS, Iodine. |
| Vitamin A (retinol) | 1500 mcg/day | NHS: having an average of 1,500 mcg a day or less of vitamin A from diet and supplements combined is unlikely to cause harm; women who are or may become pregnant should avoid vitamin A supplements. NHS, Vitamin A. |
| Vitamin E | 540 mg/day | NHS: taking 540 mg (800 IU) or less a day of vitamin E supplements is unlikely to cause harm. NHS, Vitamin E. |
How we built this
Each figure is the NHS consumer "do not take more than" amount where one exists, with the EFSA tolerable upper intake level used otherwise; the basis column names which. Figures are for supplements unless noted (vitamin A is diet and supplements combined). These are population guidance levels for healthy adults, not personal targets, and prescribed treatment doses are a separate clinical matter. Reference figures as of 2026-06-13.
Information only, not medical advice. This tool is educational and is not a substitute for a registered clinician. It does not diagnose anything and does not recommend that you take any supplement. Always read product labels and speak to your GP or pharmacist before starting, stopping or combining supplements. If you are pregnant, trying to conceive, breastfeeding or taking regular medication, some upper limits are stricter and some nutrients should be avoided; always check with your midwife, GP or pharmacist.
Read more
See the recommended daily intake lookup for the amount you actually need, the verified figures on our statistics page, and the cost per effective dose calculators. More tools are on the tools hub.
Frequently asked questions
What is a tolerable upper intake level?
It is the highest daily amount of a nutrient that is unlikely to cause harm to most people over time. For UK consumers the NHS publishes plain "do not take more than" figures for many vitamins and minerals, and where it does not, the EFSA tolerable upper intake level is used. Going over an upper limit does not mean instant harm, but it is the line at which the safety margin narrows.
Does the checker include the nutrients I get from food?
Mostly the figures shown are for supplements, because that is where people most often overdo it. For some nutrients, such as vitamin A, the limit is for diet and supplements combined, and we say so in the basis note. If you take several products, add up the same nutrient across all of them before checking; stacking multivitamins, single supplements and fortified foods is a common way to exceed a limit unknowingly.
I am over the limit. What should I do?
Do not panic, but do not ignore it either. Stop and check every product you take for that nutrient, since the total across products is what matters, and speak to your GP or pharmacist before continuing. Some nutrients, such as vitamin A in pregnancy and high-dose vitamin B6 long term, carry specific risks. This tool flags the figure; your pharmacist or GP can advise on your situation.
Why do some supplements sell doses above these limits?
High-dose products are widely sold, and a higher number is an easy marketing claim, but bigger is not automatically better and can be worse. The NHS and EFSA upper figures exist precisely because some nutrients cause harm in excess. A dose above the guidance is not necessarily unsafe for everyone, but it is a reason to check with a pharmacist rather than assume the label knows your needs.
Editor, Her Vitals
Oliver leads Her Vitals's editorial coverage of women's life-stage health and supplements. He curates and reviews existing branded products across trying to conceive, pregnancy, postnatal, perimenopause, menopause and the senior years, weighing what the evidence supports against guidance from bodies such as EFSA, the NHS and NICE, and is clear that the content is information rather than medical advice.
Last reviewed: 13 June 2026