Quick answer
- The NHS says adults need 40 mg a day, which food easily covers, and that less than 1,000 mg a day from supplements is unlikely to cause harm. It also says there is little evidence that vitamin C prevents colds.
- The reference intake on labels is 80 mg a day; one orange or kiwi provides a good share of it. Absorption drops below 50% above about 1 g a day.
- Daily vitamin C does not prevent colds in most people. It shortens them slightly: about 8% in adults.
- Plain ascorbic acid works as well as pricier forms for most people; buffered forms are gentler on the stomach.
- Germany's BfR advises at most 250 mg per daily dose in a supplement. EFSA has set no upper level, but gram doses can upset the stomach.
Key numbers
- UK daily need (NHS)
- 40 mg/day
- UK figure for supplements (NHS)
- Less than 1,000 mg/day
- More can cause stomach pain and diarrhoea.
- Reference intake on labels (NRV)
- 80 mg/day
- Safe upper level (EFSA)
- Not set
- Insufficient data; gram doses can cause stomach upset.
- Germany (BfR guidance)
- 250 mg per daily dose
- Spain
- No national maximum
- Minimum for an authorised claim
- 12 mg per daily dose
- 200 mg extra for the claim on immunity during intense exercise.
What these terms mean: NRV upper levels (NHS, EFSA) maximum levels by country daily dose
How to choose
- Ask whether you need it at all: fruit and vegetables every day usually cover vitamin C.
- For a supplement, 100–500 mg a day is plenty. Larger doses are mostly excreted.
- Choose ascorbic acid for value, or a buffered form (sodium or calcium ascorbate, Ester-C) if acid bothers your stomach.
- Don't pay extra for liposomal or "with rosehip" versions expecting better results; the evidence for an advantage is thin.
- Compare the cost per 100 mg, and check that combinations with zinc don't push zinc too high.
Vitamin C forms compared
| Form | What it is | Good to know |
|---|---|---|
| Ascorbic acid | Plain vitamin C | Cheapest and well absorbed; can be acidic |
| Buffered (sodium or calcium ascorbate) | Vitamin C as a mineral salt | Gentler on the stomach; adds some sodium or calcium |
| Ester-C | Calcium ascorbate with vitamin C metabolites | Branded buffered form; little evidence of extra benefit |
| Liposomal | Vitamin C wrapped in fat particles | Expensive; thin independent evidence |
| With bioflavonoids or rosehip | Ascorbic acid plus plant extracts | The extracts add little vitamin C themselves |
What the evidence says
Your body absorbs most of a moderate dose, but the share falls as the dose rises: according to the US National Institutes of Health, absorption drops to under 50% at intakes above about 1 g a day, and the excess leaves in urine. That is why very high-dose tablets offer little extra.
For colds, the Cochrane review of more than 10,000 people found that regular vitamin C did not reduce how many colds people caught, except under extreme physical stress such as marathons. It shortened colds slightly when taken daily. See zinc and vitamin C for colds.
What the label may legally claim
Authorised claims (GB and EU registers)
- Contributes to the normal function of the immune system
- Contributes to normal collagen formation for the normal function of blood vessels, bones, cartilage, gums, skin and teeth
- Contributes to the reduction of tiredness and fatigue, increases iron absorption and helps protect cells from oxidative stress (all from 12 mg per daily dose)
Not authorised in GB or the EU
- Preventing or curing colds
- Detox
- Anti-ageing
How health claims work (UK & EU): health claims
Products we have checked
Label data checked by NutriMetrics for products sold in Spain and Germany. UK product checks are next. Sorted alphabetically, not ranked.
| Product | Per daily dose | Sold in | Label |
|---|---|---|---|
| Solgar Ester-C Plus 1000 mg1 tablet a day | 1,000 mg | Spain · Germany (not yet confirmed) | Source |
Who should be careful
- Kidney stones: if you are prone to them, check with a doctor before taking gram doses.
- Iron overload (haemochromatosis): vitamin C increases iron absorption; ask your GP.
- Stomach upset and diarrhoea are common with doses of several grams.
FAQ
How much vitamin C should I take a day?
The NHS says adults need 40 mg a day and the reference intake on labels is 80 mg; a varied diet usually covers both. If you take a supplement, 100–500 mg a day is plenty. The NHS says less than 1,000 mg a day is unlikely to cause harm; Germany's BfR advises no more than 250 mg per daily dose.
Does vitamin C prevent colds?
Not in the general population. A Cochrane review found that taking it daily shortened colds by about 8% in adults; starting it once a cold has begun had no consistent effect.
Is liposomal vitamin C better?
There is little independent evidence that it gives a meaningful advantage for healthy people, and it costs considerably more per milligram.
Sources
- NHS — Vitamin C
- NHS — Common cold
- DHSC — Great Britain nutrition and health claims (NHC) register
- Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev, 2013
- NIH Office of Dietary Supplements — Vitamin C fact sheet for health professionals
- EFSA — Summary of tolerable upper intake levels (2024)
- Verbraucherzentrale — Maximum levels for vitamins and minerals in Europe, incl. BfR 2024 (German, 2025)
- European Commission — EU Register of nutrition and health claims
Information only, not medical advice. No product on this page is a paid placement.