The idea that your body simply "flushes out" whatever vitamins it doesn't need is only true for some of them. For others, taking more than you need doesn't just waste money — it can build up in your body to genuinely harmful levels.
Why not all vitamins behave the same way
Water-soluble vitamins (like vitamin C and the B vitamins) that your body doesn't use are largely excreted in urine — taking a large excess mostly means, bluntly, expensive urine. Fat-soluble vitamins (A, D, E, and K) are different: they're stored in fatty tissue and the liver, and chronic megadosing can lead to toxicity, liver strain, and in some cases interfere with the absorption of other nutrients.
What the NHS actually recommends
The NHS's guidance on vitamins and minerals is a deliberately conservative, evidence-based reference point — it details what each nutrient does, the recommended daily amount from a balanced diet, and the safe upper limit above which risk increases.
The starting principle is simple: most people eating a varied diet don't need to take vitamin supplements at all. The NHS specifically recommends supplementation in a small number of clear cases:
- Vitamin D: 10 micrograms daily for the general UK population during autumn and winter months, when sunlight exposure is insufficient for the body to produce enough on its own.
- Folic acid: 400 micrograms daily for anyone trying to conceive, and through the first 12 weeks of pregnancy, to reduce the risk of neural tube defects.
- Vitamin B12: recommended for people following a strict vegan diet long-term, since it's found almost exclusively in animal products.
How to actually check a supplement you're considering
- Check the back label for the %NRV (Nutrient Reference Value) or %DV figure for each ingredient.
- If a single ingredient shows something like "2000% NRV," look up that specific nutrient's safe upper limit in NHS guidance before assuming a bigger percentage is automatically better.
- If you're already eating a varied diet and don't fall into one of the three specific groups above, it's worth asking whether you actually need the supplement at all, rather than assuming more nutrients can only help.
🔎 Check the label without the maths: run your product through our free Supplement Ingredients Auditor →, and track whether it's actually making a difference with our free Supplement Tracking Diary →.
See also: to dig into the clinical evidence for a specific ingredient, check what the research actually says on Examine.com.