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N-Acetylcysteine
A cysteine donor that the EU mostly treats as a medicine, where it has been sold as a mucolytic for decades. It has no authorised health claim, because none was ever submitted for it, and it sits in one formula, Cold symptom support, at 200 mg: a third of the usual medicine dose. Its file also carries warnings for asthma and for anyone taking nitrates.
WHAT WE ARE ALLOWED TO SAY
Nothing. No claim was ever submitted.
There is no authorised health claim for N-acetylcysteine in Regulation (EU) 432/2012, and our file records that no claim was submitted for it under Regulation (EC) 1924/2006. In the EU it is considered mostly a medicine. The only EFSA opinion on file, from 2004, looked at its safety in foods for special medical purposes, not at a claim, so there is nothing on the register for us to quote and we are not going to write something that sounds like one.There is no authorised health claim for N-acetylcysteine in the EU, and none was submitted. The only EFSA opinion on file, from 2004, is about its safety, not a claim.
NAC has no authorised claim for mucus, for colds, for your liver or for antioxidant protection, however often you read otherwise. What our file describes, from its use as a medicine and from the medical literature, is a mechanism: it supplies the cysteine the body runs short of when it makes glutathione, and as a mucolytic medicine it breaks the bonds that make mucus thick. In Cold symptom support, the authorised claims come from the vitamin C, zinc and vitamin D3 next to it, not from the NAC. A mechanism is a reason to include it, not a permission to promise anything.
WHAT IT IS
The same molecule as the medicine. A fraction of the dose.
N-acetylcysteine is a form of the amino acid cysteine, and our file, drawing on the medical literature, describes three things it does. It supplies cysteine, the building block the body runs short of when it makes glutathione, the main antioxidant inside your cells. As a medicine, it is used to make bronchial mucus less thick: its free thiol group breaks the disulphide bridges in mucins. The literature also describes that same group acting on free radicals directly. And in hospital, the glutathione route is why it is given as the antidote to a paracetamol overdose, at doses calculated per kilo of body weight and far above the 200 mg here. None of this is a claim about what 200 mg in a food supplement does for you.
Synthetic N-acetyl-L-cysteine, 98% pure or more, meeting the European or US pharmacopoeia, with its batch, purity and synthetic origin documented. Our file specifies synthesis, not an animal source. It is the only form with documented clinical use.
Our NAC form sheet marks it as not stable in liquid and sensitive to oxygen. It dissolves in water, works best between pH 3 and 5, and tastes bitter. A second sheet of ours disagrees.
In the EU it has been authorised for decades as a mucolytic medicine, over the counter or on prescription depending on the country, usually at 600 mg a day. As a food supplement it sits in a grey zone: admitted in some member states, such as France and Germany, restricted or treated as a medicine in others. In the US, the FDA said in August 2022 that it would no longer object to NAC sold as a supplement while it works on a final rule.
Our own files do not fully agree. Our NAC form sheet marks it as not stable in liquid, and our formulas are liquids, so that is an open question for the formulation, not a settled one. A second form sheet in our library, filed under L-cysteine, marks NAC as stable in liquid at pH 4 to 7, so our files contradict each other on this point. The ingredient file gives a half-life of 5.6 hours and says about 30% leaves through the kidneys and the rest through the liver; the pharmacokinetic sheet lists only the kidneys and has no confirmed half-life. It puts the share of an oral dose that reaches your blood at 4 to 10%. Its regulatory status, in the EU and the US, is still marked as pending confirmation in our file. The file was rebuilt in May 2026 and is still pending review by a clinician.Our two form sheets disagree on whether NAC is stable in liquid, and our files disagree on how it is cleared. Its regulatory status is still pending confirmation, and the file is pending review by a clinician.
WHERE IT APPEARS
One of the twenty-nine carries it.
NAC is only in Cold symptom support, a BOOST formula for when you have a cold. It sits at 200 mg a day, split across the morning and the night window, down from the usual 600 mg a day, because our notes put 200 mg as the most NAC a food supplement can carry in Spain. Our file gives 600 mg a day for 4 to 12 weeks as the minimum effective dose, so 200 mg for a week at most is below it on both counts. On its own, our file says NAC is best taken between meals, and fine with food if it upsets your stomach; the formula is served preferably with food. The course runs for seven days at most: if your symptoms last longer, see a doctor. Stop taking it straight away if you notice signs of liver problems: the pelargonium in the same formula has reported cases. The formula is not for pregnancy, autoimmune conditions, immunosuppression or anyone on vitamin K antagonist anticoagulants.
THE CEILING
No official limit. Our file caps it at 1,800 mg a day.
EFSA has not published a tolerable upper intake level for NAC, so there is no official ceiling to draw here. The ceiling is our own: our file sets 1,800 mg a day as the most you should get, added up across formulas, which is the top of the 600 to 1,800 mg a day range it reports for NAC as a supplement. At 200 mg, the one formula that carries it is well under that, and no engine rule has been written for it yet. No limit is not the same as no risk.EFSA has not published an upper intake level for NAC, so the cap is ours: 1,800 mg a day, across everything you take. No limit is not the same as no risk.
Our file flags glutathione, free cysteine and SAMe as working through the same sulphur pathway as NAC, so their totals are reviewed together. With L-methionine in the same plan, methionine and cysteine together stay at or under 2 g a day.
By mouth: nausea, vomiting in up to 33%, diarrhoea, reflux and a characteristic sulphurous taste. Given into a vein, which is not how we serve it, allergic-type (anaphylactoid) reactions linked to the speed of the infusion appear in up to 18% of patients, mostly mild or moderate and rarely severe. It can also skew two lab results: a falsely raised INR and a false positive for ketones in urine.
Never if you are hypersensitive to NAC. Asthma or sensitive airways: there is a risk of the airways tightening instead of relaxing, mostly when it is inhaled. An active stomach ulcer, because by mouth it can irritate the stomach. Pregnancy: no documented risk to the baby at therapeutic doses, but only under supervision, and the formula that carries it rules pregnancy out. Breastfeeding: limited data, and after overdose treatment some guidelines advise expressing and discarding milk for 30 hours. Heart failure or a heart muscle sensitive to fluid volume: the caution is about the volume of the intravenous form. The label would say to take care if you have asthma, and to speak to your healthcare professional if you take nitroglycerin or other nitrates, or activated charcoal.
WHAT IT REACTS WITH
Six documented pairs. Three medicines from its own file.
NAC is one of the 140 ingredients in our library, so it has 139 possible partners. Six of them are documented in our interaction table, out of the 443 pairs on file: two about timing, one about totals and three that work alongside it. Its own file adds three medicines that are not in our drug table yet.
Charcoal and NAC bind each other in the gut, so less of both is absorbed. NAC's own file says to keep them at least 2 hours apart; our interaction table says at least 4, and the two have not been reconciled yet. Psyllium husk slightly reduces absorption: at least 1 hour apart.
NAC supplies the raw material for glutathione and sulforaphane from broccoli prompts the enzymes that make it, so our file recommends them together. Selenium is a cofactor of the enzyme that uses glutathione, and taurine conjugates bile acids, a complementary route: both are compatible. L-methionine is the one with a limit. The body makes cysteine from it, so the two partly do the same job, and together they stay at or under 2 g a day.
From its own file: nitroglycerin and other nitrates, where NAC may add to their effect on blood vessels, with low blood pressure and headache; carbamazepine, whose levels in your blood may drop; and anticoagulants such as warfarin or acenocoumarol, where the INR may rise, a risk our file rates as theoretical and mild.
None of NAC's medicine interactions is in our drug table yet: the warnings about nitrates, carbamazepine and anticoagulants come from its own file, not from checked pairs. The overlap it flags with glutathione, free cysteine and SAMe is not documented as a pair either. Across the library, 443 of the 9,730 possible pairs 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.None of NAC's medicine interactions is in our drug table yet. Across the library, 443 of the 9,730 possible pairs are documented, which is 4.55%. The rest are not safe, they are simply unchecked.
SOURCES
Everything on this page, with its reference.
Reviewed by VION nutrition team · last reviewed 16 September 2026Read the introduction to NAC (N-acetylcysteine) →
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