By Dr Sarah Adams, doctor and longevity health writer. Prices checked 10 November 2026.
I added N-acetyl cysteine to my own routine two winters ago after reading the Genoa influenza study, in which older adults on 1,200mg a day were far less likely to develop symptomatic flu, and I have kept it there for the glutathione support that matters more to me as I move through my fifties. What I had not done, until this autumn, was compare the products properly. So from August to early November I worked through nine NAC supplements available to UK buyers, one at a time, keeping notes on capsule size, smell, how my stomach tolerated each on an empty stomach, how many capsules it took to reach the doses used in the clinical trials, and what the label did and did not tell me. This is not a laboratory test and I make no claim that I could feel one brand working better than another; NAC's effects are measured in blood and in trial endpoints, not in how you feel on a Tuesday. It is a reviewer's account of nine bottles, their labels and their prices, and the one I have gone back to is Welzo Ultra Purity NAC 1500.
What I was looking for
Four things. First, dose per capsule: the trials with the best results used 1,200mg a day for lungs and immunity and 1,200 to 2,400mg in the psychiatric work, so a 500mg or 600mg capsule means two or three a day and I wanted to know how that felt in practice. Second, what else is in the capsule: NAC is a single amino acid and the honest products have two or three ingredients, not eight. Third, evidence of testing: a statement of third-party testing at minimum, published certificates ideally. Fourth, cost at a real dose, which I calculated as the daily price of 1,200mg rather than the per-bottle figure that makes small capsules look cheap. The same four questions shape all of our ranking pieces, from the best NMN supplements to the best magnesium, because they are the questions a label can actually answer.
Why NAC in the first place
N-acetyl cysteine is the acetylated form of the amino acid cysteine, which is the rate-limiting ingredient your cells need to make glutathione, the main antioxidant inside every cell and the molecule your liver's detoxification enzymes depend on. Swallowing glutathione itself does little because it is broken down in the gut, so NAC is the standard way to raise it. NAC has been a licensed medicine since the 1960s (it remains the hospital antidote to paracetamol overdose and a prescribed mucolytic for chronic bronchitis), which means it has far more human trial data behind it than most supplements. Three findings persuaded me personally:
- In the PANTHEON trial (Lancet Respiratory Medicine, 2014), 1,006 people with COPD who took 600mg twice daily for a year had 22% fewer exacerbations than placebo.
- In the Genoa study (European Respiratory Journal, 1997), 262 mostly older adults took 600mg twice daily over winter; the same proportion caught influenza, but only 25% of infected NAC users developed symptoms against 79% on placebo.
- In the Baylor College of Medicine GlyNAC trial (Journals of Gerontology, 2023), older adults given glycine plus NAC for 16 weeks corrected their glutathione deficiency and improved oxidative stress, mitochondrial function, insulin resistance, gait speed and grip strength, with several markers moving back toward young-adult levels.
Every one of those studies used 1,200mg a day or more. Keep that number in mind as you read the labels below, because most NAC bottles are sold as if 600mg a day were the dose.
The nine, ranked
1. Welzo Ultra Purity NAC 1500 – the one I kept buying
1,500mg per two-capsule serving (750mg per capsule), 60 vegetarian capsules, £19.99 (RRP £39.99). Third-party tested for identity, potency and contaminants (brand statement). Two capsules daily on an empty stomach with water. 94 reviews on the product page.
This was the only product of the nine where the label dose and the trial dose agreed without my having to do arithmetic. Two capsules give 1,500mg, which sits comfortably above the PANTHEON and Genoa doses and inside the range the psychiatric trials used, and 750mg capsules are no larger in the hand than the 600mg ones from other brands. I took it on an empty stomach each morning for four weeks with no digestive complaint, and the sulphur smell when you open the bottle, which every NAC product has, was no worse than the practitioner brands. Welzo states that batches are third-party tested, lists no proprietary blend, and ships from a UK warehouse with UK returns, which matters when you are reordering monthly. At £19.99 it works out at 53p a day for 1,500mg; several products below are cheaper per milligram, but none gets to a clinical dose in two capsules.
My criticisms are about the paperwork. The capsule is described only as "vegetarian" without naming the material, the excipients are not listed online, and no certificates of analysis are posted. The supplement-facts panel also says "60 servings" for a 60-capsule bottle with a two-capsule serving, which should read 30. I would like all of that fixed, and I have said so to the brand, but none of it changed what was in the capsule or how it suited my routine. Readers should also know that AllHealthStore and Welzo are part of the same group of companies; I have tried to make the reasoning transparent enough that you can disagree with it.
2. BioCare N-Acetyl Cysteine – the practitioner heavyweight
500mg per capsule, 90 capsules, 1,500mg per daily intake of three capsules, £38.39–£39.95. Ingredients: N-acetyl cysteine, HPMC capsule, silicon dioxide, magnesium stearate. Vegan; free from the 14 major EU allergens. UK brand.
BioCare is the Birmingham practitioner brand UK nutritional therapists have dispensed since the 1980s, and this is the only other product here whose label directs you to 1,500mg a day: one capsule three times daily before food. I liked the discipline of that, and the formula is clean, but three capsules spread through the day is a commitment I kept forgetting by the third week, and at nearly £40 for a month it is the most expensive way to reach the dose in this review (£1.30 a day). If your practitioner prescribes BioCare you will be well served; as a self-funded daily supplement it is hard to justify over the Welzo product, which gives the same 1,500mg in two capsules for half the price.
3. Viridian High Potency NAC – the ethical choice
600mg per capsule, 60 capsules, £29.90. Ingredients: N-acetyl L-cysteine in a base of alfalfa, spirulina and bilberry, plant cellulose capsule. Vegan; produced via fermentation; no GMO or palm oil. UK brand.
Viridian, from Daventry, is the brand I reach for when I care about how a supplement is made as much as what is in it: no artificial fillers, a botanical base instead of stearates, Leaping Bunny cruelty-free certification and a long record of charitable giving. The NAC is produced by fermentation rather than chemical synthesis, which is unusual and worth knowing. In practice it was a pleasant capsule with the least noticeable smell of the nine, and the label allows one or two a day. The problem is price: two capsules for 1,200mg costs £1.00 a day, and the 60-count lasts only a month at that dose. It earns third place for its integrity, not its value.
4. Cytoplan NAC – the quiet overachiever
500mg per capsule, 60 or 120 capsules, £12.66 at Healf (RRP £21.99). Ingredients: N-acetyl-L-cysteine, brown rice flour, plant cellulose capsule. Vegan. UK brand.
Cytoplan is a Worcestershire practitioner company owned by a charitable foundation, and its NAC has the shortest ingredient list in this review bar one: the amino acid, rice flour and a cellulose shell. At the Healf price it is also remarkably cheap, 51p a day for 1,000mg from two capsules (the 500mg size makes 1,200mg awkward; you take two or three). I found it well tolerated and would happily recommend it to anyone who wants a simple, UK practitioner-grade NAC at a high-street price. It sits fourth only because the 500mg capsule is the wrong size for the trial doses and the brand, like most, does not publish batch certificates.
5. Sunday Natural NAC 600mg – the purist's capsule
600mg per capsule, 120 capsules, £14.90. Ingredients: N-acetyl-L-cysteine, HPMC capsule. Raw material stated as over 98.5% pure; systematic independent laboratory testing stated; vegan; produced and encapsulated in the EU.
Sunday Natural is a Berlin company with a UK storefront and a reputation among supplement obsessives for two-ingredient formulas, and this is exactly that: NAC and a cellulose shell, nothing else. The brand states a purity specification and independent laboratory testing, which more UK brands should copy. At £14.90 for 120 capsules a 1,200mg day costs 25p, the best value of any tested product in this review. Why not higher? Shipping from Germany took five working days when I ordered, returns are to the EU, and there is no published certificate for the batch I received. For a stock-up order it is excellent.
6. Vitabright NAC 600mg – the Amazon favourite that deserves its rating
600mg per capsule, 180 capsules, £19.99. Ingredients: N-acetyl-L-cysteine, rice flour, HPMC capsule. Made in the UK in BRC-accredited, GMP-compliant facilities; third-party tested for purity and heavy metals (brand statement). Vegan.
Vitabright is a Hampshire company that sells mostly through Amazon, where this NAC carries thousands of reviews, and it was better than I expected: a clean three-ingredient capsule, a UK manufacturing statement and a third-party purity testing claim that most budget brands do not make. The 180-count makes a 1,200mg day cost 22p. The label tells you to take it after a meal rather than on an empty stomach, which runs against the absorption advice but will suit anyone who finds NAC upsets their stomach. A very good budget pick; it ranks below Sunday Natural only because the testing statement is less specific.
7. Nutravita NAC 600mg – the supermarket option
600mg per capsule, 150 capsules, £14.39 (Tesco marketplace) to £19.99 (direct). Ingredients: N-acetyl L-cysteine, HPMC capsule, microcrystalline cellulose, dicalcium phosphate. Made in the UK. Vegan.
Nutravita is now stocked by Tesco, Superdrug and Debenhams online as well as Amazon, which makes it the easiest NAC in this review to add to a weekly shop. Five months' supply at one a day, or ten weeks at the 1,200mg trial dose, for under £15 is 19p a day. It has two bulking agents where Vitabright has one and Sunday Natural has none, and the brand makes no third-party testing statement, which is why it sits below both despite the lower price. Perfectly serviceable.
8. Bulk N-Acetyl L-Cysteine Powder – for people who hate capsules
700mg per scoop, 100g pouch (about 140 servings), £9.99 (regular £12.99); also 500g and 1kg. Ingredients: 100% N-acetyl L-cysteine. UK brand, Colchester.
I included one powder because capsule-averse readers ask about it, and Bulk's is the obvious UK choice. The maths is absurd: 1,400mg from two scoops costs about 14p a day, cheaper than anything else here by a wide margin. The catch is the taste. NAC powder is intensely sour and sulphurous and I could only manage it stirred into orange juice, which is at least the acidic medium that improves absorption. If you can tolerate it, nothing matches the cost; if you are unsure, buy the 100g before committing to a kilo.
9. Allergy Research Group NAC 500mg – the tablet for the hypersensitive
500mg per tablet, 120 tablets, £40.81–£43.54 (Landys Chemist via Cosmetify). US practitioner brand, hypoallergenic formulation.
Allergy Research Group was founded in 1979 by the late Stephen Levine specifically for chemically sensitive patients, and its NAC is a tablet rather than a capsule, which some people with cellulose or rice sensitivities prefer. It is the product I would send a patient to if every capsule in this list had disagreed with them. For everyone else it is the most expensive NAC per milligram I tested (over 80p a day at 1,200mg), the tablets are large, and UK availability is through a handful of importing pharmacies. A specialist product, ranked last for value rather than quality.
Side by side
| Rank | Product | NAC per unit | Pack | Other ingredients | UK price | Daily cost at 1,200mg |
|---|---|---|---|---|---|---|
| 1 | Welzo Ultra Purity NAC 1500 | 750mg capsule (1,500mg per 2) | 60 | Vegetarian capsule (not specified) | £19.99 | 53p (at 1,500mg) |
| 2 | BioCare N-Acetyl Cysteine | 500mg capsule | 90 | HPMC, silicon dioxide, magnesium stearate | £38.39–£39.95 | £1.04–£1.30 (at 1,500mg) |
| 3 | Viridian High Potency NAC | 600mg capsule | 60 | Alfalfa, spirulina, bilberry base; cellulose capsule | £29.90 | £1.00 |
| 4 | Cytoplan NAC | 500mg capsule | 60 / 120 | Brown rice flour, cellulose capsule | £12.66–£21.99 | 51p–88p (at 1,000mg) |
| 5 | Sunday Natural NAC | 600mg capsule | 120 | HPMC capsule only | £14.90 | 25p |
| 6 | Vitabright NAC | 600mg capsule | 180 | Rice flour, HPMC capsule | £19.99 | 22p |
| 7 | Nutravita NAC | 600mg capsule | 150 | HPMC, microcrystalline cellulose, dicalcium phosphate | £14.39–£19.99 | 19p–27p |
| 8 | Bulk NAC Powder | 700mg scoop | 100g | None | £9.99 | 14p (at 1,400mg) |
| 9 | Allergy Research Group NAC | 500mg tablet | 120 | Not published online | £40.81–£43.54 | 82p–87p |
Daily cost is the pack price divided by total NAC content and multiplied by the dose shown. Prices are the lowest in-stock UK price I found on 10 November 2026 and will move.
What twelve weeks taught me
The dose, not the brand, is the decision. Every product here contains the same molecule. What varied was how many capsules it took to reach 1,200mg and whether the label even acknowledged that number. Only Welzo and BioCare did.
Empty stomach works for most people. I took every product before breakfast with water and had no trouble; NAC absorbs better in an acidic environment and the Welzo label says so. Two friends who tried it found it made them queasy, and for them the Vitabright advice to take it after food is sensible even at the cost of some absorption.
The smell is normal. Every bottle smelt faintly of struck matches on opening; Viridian least, the powder most. It is the sulphur in the molecule, not a sign of degradation.
Pair it with glycine if you are taking it for ageing. The Baylor work used glycine and NAC together because both are limiting for glutathione synthesis. A spoon of plain glycine powder alongside any product here recreates the ratio cheaply. NAC also sits naturally with the mitochondrial supplements we cover in our guides to PQQ and urolithin A, and with the NAD+ precursors, since glutathione is what keeps other antioxidants in their working state. For the wider picture see our ranked anti-ageing supplements.
Separate it from minerals. NAC chelates zinc, copper and iron, so I took it two hours away from my vitamin D3 and K2 and mineral supplements.
Safety
NAC is well tolerated: in PANTHEON a year at 1,200mg produced no more adverse events than placebo. The common complaints are nausea and loose stools, which food usually solves. It can enhance the effect of nitrate medicines such as glyceryl trinitrate, so check with a pharmacist if you take them; it may increase coughing initially in people with bronchitis because it is doing its job of thinning mucus; and anyone with cystinuria, a peptic ulcer, a bleeding disorder or who is pregnant, breastfeeding or receiving cancer treatment should ask their doctor before starting. Readers who have seen headlines about NAC being "banned" should know that this refers to a US regulatory dispute resolved in 2022 when the FDA confirmed it would not object to NAC supplements; in the UK it has always been lawfully sold as a food supplement.
My verdict
If I were buying one bottle tomorrow it would be Welzo Ultra Purity NAC 1500, because it is the only UK-shipped product that delivers a clinically supported dose in two capsules with a testing statement, for a price that undercuts the practitioner brands by half. If I were stocking a cupboard for the year on a budget, Sunday Natural or Vitabright. If I wanted the most carefully made product regardless of cost, Viridian. And if capsules were out of the question, Bulk's powder in a glass of orange juice, held at arm's length.
Medical disclaimer: this article reflects one reviewer's experience and the published literature; it is general information, not individual medical advice, and NAC supplements are not treatments for COPD, influenza, psychiatric illness or paracetamol poisoning. Speak to your GP or pharmacist before taking NAC if you take prescribed medicines, are pregnant or breastfeeding, or have a medical condition. AllHealthStore and Welzo.com are part of the same corporate group; all product information is taken from manufacturers' published labels and UK retailer listings on 10 November 2026.