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Vitamin C
A water-soluble vitamin with fifteen authorised EU health claims, from your immune system to collagen and iron absorption. It sits in nine of our formulas at anything from 80 to 1,000 mg. EFSA has never set an upper limit for it, so the ceilings we work to come from the US, France, Germany and our own file.
WHAT WE ARE ALLOWED TO SAY
Fifteen claims. All of them authorised.
These are the fifteen claims on the EU register for vitamin C, in our own faithful translation of the Spanish wording our file holds, and we do not paraphrase them into something that sounds stronger. Fourteen carry the same condition: the product has to be at least a source of vitamin C under Regulation (EC) 1924/2006. The exercise one is narrower: it only holds for a product that provides 200 mg a day, with the benefit coming from 200 mg a day on top of your recommended intake. Our formulas serve 80 to 1,000 mg, which is 100% to 1,250% of the NRV, and the two at 80 mg do not reach the exercise claim.These are the fifteen EU-register claims for vitamin C, in our own faithful translation of the Spanish wording on file, and we do not paraphrase them. Fourteen need the product to be at least a source of vitamin C; the exercise one needs 200 mg a day. Our formulas serve 100% to 1,250% of the NRV.
None of the fifteen is a claim about colds, inflammation or muscle recovery, even though vitamin C sits in formulas named after all three. In the cold formulas it carries the immune claims, and the exercise one is about your immune system, not your muscles. The inflammation and muscle formulas are registered under an omega-3 claim, not a vitamin C one. The cold research we cite, a Cochrane review, is a reason to include it, not a permission to promise anything.
WHICH FORM
Two files, two answers. The form is not fixed yet.
The fifteen claims attach to vitamin C, not to a particular salt, so the form is not a claim argument and we do not use it as one. None of our nine formulas records which form it uses yet, and our own files do not agree on which one to prefer.
The vitamin itself. Our form file lists it as the preferred form, together with magnesium ascorbate, which the same file notes does not acidify.
Sodium or calcium L-ascorbate, buffered. Our ingredient file prefers it for better stomach tolerance than pure ascorbic acid, and mentions a liposomal form for high doses.
Our form file marks it as not stable in liquid, and sensitive to light, oxygen and heat. It keeps best between pH 3 and 5, dissolves in water and tastes bitter. How that is handled in a liquid dose is not documented yet, and we would rather write that down than leave it out.
Better stomach tolerance is what our notes record, not an authorised claim, so you will not read it on a label. And there is an open point we would rather write down: our own files mark vitamin C as not stable in liquid, VION doses are liquid, and the form in each formula is still to be decided.Better stomach tolerance is not an authorised claim. And our own files mark vitamin C as not stable in liquid, while VION doses are liquid.
WHERE IT APPEARS
Nine of the twenty-nine carry vitamin C.
Two CORE formulas, four BOOST and three blood-test formulas, two of which are still in development. The doses run from 80 mg to 1,000 mg, and the two 1,000 mg boosts are split between morning and night. That spread is why vitamin C has to be counted across your plan, not formula by formula. The last column says why vitamin C is in each one, from our notes, and names the claim the formula itself is registered under where that is a different one.
THE CEILING
No EFSA limit. Our own cap is 1,000 mg a day, 500 mg past two formulas.
EFSA has not set an upper limit for vitamin C: our file records not enough data, and a long history of safe use up to 1,000 mg a day. The references we hold run from 250 mg a day in a supplement (Germany's BfR) through 1,000 mg with diet included (France's ANSES) to 2,000 mg for adults (US). Our own file sets two caps on the total: 1,000 mg a day when vitamin C sits in two formulas, which the two 1,000 mg boosts reach on their own, and 500 mg a day when it sits in more than two, which any of our four formulas at 500 mg or more reaches on its own.EFSA has not set an upper limit for vitamin C. The references we hold run from 250 mg in a supplement (Germany) to 2,000 mg (US), and our own cap is 1,000 mg a day across two formulas and 500 mg across more than two.
Our file sets two figures for the summed daily total: 1,000 mg when vitamin C is in two active formulas, a working figure chosen in the absence of an EFSA limit to keep a margin for your stomach, and 500 mg when it is in more than two. Neither is written into an engine rule yet, so we would rather say that than imply the check is automatic. Four of our formulas are above the 250 mg Germany's BfR suggests for a supplement.
Our file asks for vitamin C to be split across the day, two or three times, to keep blood levels steady: above 1,000 mg in a single dose, more than half of it is not absorbed. That is why the two 1,000 mg formulas are served morning and night. With food it is easier on your stomach; above 1,000 to 2,000 mg in one dose, the usual side effects are diarrhoea, cramps and nausea.
With kidney disease, take care: high doses over time are linked to calcium oxalate kidney stones in people prone to them (hyperoxaluria), and our file asks you to stay under 500 mg a day if you have chronic kidney disease. It is a relative contraindication with hereditary haemochromatosis, iron overload or thalassaemia, because it adds to the iron your body builds up. With G6PD deficiency, high intravenous doses can cause haemolysis; oral doses carry less risk, but ask your doctor. If you are in cancer treatment, ask your oncologist before starting: the data on whether it protects or interferes are mixed. If you take anticoagulants such as warfarin, acenocoumarol, apixaban or dabigatran, ask your doctor first. Our file rates vitamin C safe at standard doses with anticoagulants, but every formula that carries it is ruled out for people on vitamin K antagonists such as warfarin, and three (Anti-inflammatory & recovery, Systemic inflammation and Muscle damage) for any anticoagulant. Under 18, the limits on file are lower: 400 mg a day at 1–3 years, 650 mg at 4–8, 1,200 mg at 9–13 and 1,800 mg at 14–18, and Acute energy is not for under-18s at all. In pregnancy and breastfeeding our file rates vitamin C itself safe up to 2,000 mg a day. The formulas that carry it have their own exclusions, and we list them all here: three (Immunity, Acute immunity and Cold symptom support) are ruled out in autoimmune disease and immunosuppression, and Acute immunity also in severe atopy; five (Immunity, Iron, Anti-inflammatory & recovery, Systemic inflammation and Muscle damage) in liver disease; Iron in haemochromatosis; and two (Acute energy and Cold symptom support) in pregnancy, with Acute energy also ruled out while breastfeeding. Apart from haemochromatosis, which is on vitamin C's own list too, those come from other ingredients in the formulas. For vitamin C itself, our file lists no contraindication for liver or heart disease, and it contains none of the fourteen allergens that must be declared in the EU.
WHAT IT REACTS WITH
Documented pairs, not hunches.
Vitamin C is one of the 140 ingredients in our library, so it has 139 possible partners. We have documented 12 of them, out of the 443 pairs on file. Ten work together: besides iron, collagen and hyaluronic acid, there is vitamin E, which it regenerates, zinc, which our cold formula pairs it with, and beta-carotene, L-carnitine, L-cysteine, manganese and maritime pine bark, which can share a dose with it. Two need spacing. Our ingredient file also notes a mild antagonism with copper at high chronic doses, where it can lower ceruloplasmin; that pair is not in our documented interaction table yet, so it is not counted in the 12.
Vitamin C turns iron into a form your gut takes up more easily: in our notes, 50 mg of it doubles the absorption of non-haem iron and 250 mg quadruples it. Our library pairs them in the same dose, at 50–250 mg of vitamin C for each dose of iron, and Iron (ADAPT-03) carries 80 mg. Your body also needs it to build collagen, so our rule is at least 80 mg of vitamin C whenever collagen or hyaluronic acid is in your plan.
Above 500 mg in one dose, vitamin C may break B12 down. The evidence comes from the lab and is mixed and weak in people, but our rule keeps them 2 hours apart. At everyday doses, up to 200 mg of vitamin C with up to 500 µg of B12, they can share a dose. Acute energy carries both in the same dose, with vitamin C at 500 mg: above the 200 mg our rule clears for sharing, and just at the edge of the 500 mg that would trigger the two-hour gap. Our file does not resolve that middle ground, so we write it down rather than assume it is fine. Above 1 g, vitamin C also turns selenite into a form that is absorbed less well, so selenite is kept 2 hours from vitamin C doses above 500 mg. With selenomethionine there is no restriction.
None of these is in our medication matrix yet; they come from our ingredient file. With cancer treatment, ask your oncologist first: some chemotherapy agents may be affected by its antioxidant action. With deferoxamine, vitamin C can increase the heart toxicity of iron, rated major. With aluminium antacids it raises aluminium absorption, a risk with kidney disease. Very high doses, above 1 g, may lower your INR on warfarin, though the data are limited. Our file also lists statins taken with niacin, where antioxidants reduce the rise in HDL, and oestrogens, including the pill, whose levels it can raise. If you take any of them, ask your doctor before starting.
443 of the 9,730 possible pairs in our library are documented, which is 4.55%. The rest are not "safe", they are simply unchecked, and we would rather write that down than let the number look like a badge.443 of the 9,730 possible pairs in our library are documented, which is 4.55%. The rest are not safe, they are simply unchecked, and we would rather write that down than let the number look like a badge.
SOURCES
Everything on this page, with its reference.
Reviewed by VION nutrition team · last reviewed 16 September 2026
140 INGREDIENTS · 64 IN USE TODAY
Every one of them has a page like this.
What it is, what we are allowed to say about it, which formulas carry it, what it reacts with and where each of those statements comes from. No proprietary blends, no hidden amounts.