NAC dosage and evidence
Written by Aaron CuhaReviewed Sep 2026
The short answer
NAC is what the body uses to make glutathione. It is FDA-approved to thin mucus and as the standard antidote for a Tylenol (paracetamol) overdose. It is also studied for mental health and lung problems.
Evidence grade for NAC: Limited. The rule: people have taken it in a published study, but fewer than 100 of them. The sum on this page: 2 completed trials, 15 people given it. A grade counts how much has been done to people, not whether it works.
- People given it
- 15
- Human studies
- 2
- Found nothing
- 0
Dose
Approved medicine. No human dose established for unlabelled uses
Labeled amounts sit on the prescribing information. This page records what trials measured, not a personal dose.
FDA-approved (to thin mucus, and as an antidote for acetaminophen overdose); also sold as a supplement
No first-hand reports gathered yet. That is a gap in what we have collected, not a finding that nothing has been reported.
In plain English
In plain English, from Aaron
This is how I would explain it to a friend. The evidence, with the numbers, is further down the page.
NAC is a pill the body turns into glutathione, its main antioxidant. Hospitals use it for one big job. It saves the liver after a Tylenol overdose. It is also approved to thin mucus. You can buy it as a supplement too.
What people take it for
- Raising glutathione, the body's own antioxidant.
- Thinning mucus in the chest.
- Mood, cravings and other mental health problems.
- Liver protection, because of its use in overdoses.
What studies in people showed
The strong proof is for Tylenol poisoning. Records from 2,540 people treated after an overdose were pooled. When NAC started within 10 hours, serious liver damage happened in 6.1 percent. Started within 8 hours, it protected people no matter how much drug was in their blood. The first report of NAC given into a vein was in 15 poisoned patients. The liver stayed normal or close to normal in 11 of the 12 treated within 10 hours. Nobody was left untreated on purpose, because that would not be safe. For mental health and brain problems, a review found early good signs. Results changed from one condition to the next, and bigger studies are still needed.
What people report
Reports, not study results
The good
- Started within 8 to 10 hours of a Tylenol overdose, it protects the liver. That is why it is standard hospital care.
The bad
- Given into a vein, it can cause a reaction that looks like a bad allergy. Flushing, rash, wheezing or a drop in blood pressure are the signs. That is the main warning on its label.
- For mood and brain problems, the results are early and do not agree.
Where these come from: The results and the warning come from the studies and the FDA label on this page. We have not collected user reports on this one yet.
My bottom line
For a Tylenol overdose, NAC is real medicine and it saves livers. For everything else it is a supplement with early, mixed results. If you want it for mood or cravings, get your blood work done and talk to your doctor first.
An opinion, not a finding. I am a coach, not a doctor.
What it has been measured to do
Nothing indexed yet
The 4 citations on this page do not report a result for any of the 36 goals indexed here. Most of what sits here is something else: a listing of a planned study, a study of how the body handles the drug, a safety report or a government record. None of those tests whether it works.
When this earns a spot
The owner's trigger is raised liver enzymes. The approved uses in people are paracetamol (Tylenol) overdose and thinning mucus. Those uses do not automatically carry over to a longevity capsule. If you have asthma, or take a long list of bottles, talk to a doctor.
Aaron's list, tier 2
Bloodwork that belongs beside the bottle
Bring every bottle, including tea extracts, to the blood draw.
Test again after about 90 days. If that blood number did not move, stop.
- AST also comes from muscle.
- A new detox stack plus NAC is two changes at once.
Reading the number
ALT or AST that stays high means see a doctor this week, not go shopping. If enzymes were the reason and they did not move, stop the NAC.
What these tests mean: Liver enzymes.
What people typically order
Ask for ALT, AST and GGT. The Archive does not order liver tests.
Show full evidence
What is NAC?
NAC is what the body uses to make glutathione. It is FDA-approved to thin mucus and as the standard antidote for a Tylenol (paracetamol) overdose. It is also studied for mental health and lung problems.
NAC, short for N-acetylcysteine, gets into the body well when swallowed. The body turns it into cysteine, which it uses to make glutathione. The FDA approves it to thin mucus. Given into a vein, it is the standard antidote for an overdose of acetaminophen, also called paracetamol or Tylenol. That use has strong evidence. In records from 2,540 overdose patients, serious liver damage fell to 6.1% when NAC was started within 10 hours. It has also been studied for mental health, addiction and breathing problems, with less steady results.
How does NAC work?
It gives the body cysteine, which it uses to refill glutathione. It also mops up harmful oxygen molecules directly. In the brain it changes signaling by glutamate, a chemical messenger.
The evidence, in charts
Fig. 1a · how many people
2,555people, across 2 studies in people cited here
| Study | People | Share |
|---|---|---|
| New England Journal of Medicine 1988 | 2,540 | 99% |
| The Lancet 1977 | 15 | 1% |
One study holds 99% of these people, so the total rests more on one study than its size suggests. Counts are the number of people each study on this page says it signed up. That includes studies that only watched people and gave nobody the compound. 1 more study in people gives no headcount and is not counted here. Studies still signing people up are left out, and only studies cited on this page are counted.
Fig. 1b · evidence mix
3 of 4 sources here are studies in people. The rest is not.
- Study in people · done in people375%
- Review of studies · sums up other studies125%
Counted from the list of sources on this page. It counts only what we cite, so there may be more studies out there. A review counts once, however many studies it sums up.
Fig. 2 · evidence over time
The studies cover 4 different years, 1977 to 2025, counted from the list of sources on this page.
Fig. 3 · legal status at a glance
US
Approved
UK
Approved
AU
Approved
CA
Approved
Approved in all four countries shown. This is what the law says, not a verdict on the science. See Legal status below for the full text and any notes.
Fig. 5 · what the molecule is
- Kind of compound
- Supplement
- Molecule weight
- 163.2 Da
- Half-life
- About 5.5 hoursShort, 1 to 6 hours
- Chain length
- None on file
No amino acid sequence is on file for NAC, which is expected: a supplement is not built from amino acids.
The studies we cite
- Study in people1988Efficacy of oral N-acetylcysteine in the treatment of acetaminophen overdose: analysis of the national multicenter study (1976 to 1985)
NAC works, and this is the study that made it standard care for paracetamol poisoning. Doctors pooled records from 2,540 people treated across the country after an overdose. Among those given NAC by mouth within ten hours, serious liver damage happened in about one in sixteen. Starting within eight hours protected people whatever their blood drug level was. Nobody here was picked by chance to go without NAC, because withholding it would have been unsafe.
In 2,540 treated overdose patients, hepatotoxicity fell to 6.1% when NAC was started within 10 hours; NAC was protective regardless of initial acetaminophen level when given within 8 hours.
- Study in people1977Treatment of paracetamol (acetaminophen) poisoning with N-acetylcysteine
This is the first time anyone gave NAC into a vein for paracetamol poisoning, and it worked. Fifteen poisoned patients were treated. Of the twelve who got it within ten hours, eleven kept normal or near normal liver tests. The drip schedule still used today comes from this report. Everyone here was treated, so there was no untreated group to compare against. It is a first look rather than a trial, and the large studies that followed are what settled the question.
First report of intravenous NAC in 15 poisoned patients: liver function stayed normal or near normal in 11 of 12 treated within 10 hours; established the IV regimen.
- Study in people2025Acetadote (acetylcysteine) injection: prescribing information
This is the regulator's own instruction sheet, not a study. It approves NAC given into a vein for people who have swallowed a dangerous amount of paracetamol. The drip should start within eight to ten hours of the overdose to prevent or limit liver damage. The label's main warning is a reaction that looks like a severe allergy, with flushing, rash, wheeze or a drop in blood pressure. It carries no evidence of benefit for anything else, because it was never written to.
FDA-approved label: IV acetylcysteine given within 8 to 10 hours of a potentially hepatotoxic acetaminophen ingestion to prevent or lessen liver injury; anaphylactoid reactions are the key warning.
- Review of studies2015Clinical trials of N-acetylcysteine in psychiatry and neurology: a systematic review
A review of NAC studies in mental health and brain conditions. Early results look good for several conditions, but they vary by condition. Bigger studies with a comparison group are still needed.
Favorable but early evidence in several psychiatric and neurological conditions; larger controlled trials still needed and results vary by indication.
Common questions
Has NAC been tested in people?
Yes. 15 people given it across 2 completed trials cited here, 0 of which found nothing. NAC is what the body uses to make glutathione. It is FDA-approved to thin mucus and as the standard antidote for a Tylenol (paracetamol) overdose. It is also studied for mental health and lung problems.
What is the NAC dosage?
Approved medicine. No human dose established for unlabelled uses. Labeled amounts sit on the prescribing information. This page records what trials measured, not a personal dose. FDA-approved (to thin mucus, and as an antidote for acetaminophen overdose); also sold as a supplement
Is NAC FDA-approved?
FDA-approved (to thin mucus, and as an antidote for acetaminophen overdose); also sold as a supplement
Is NAC the same as glutathione?
No. NAC is what the body uses to make glutathione. Much more of it gets into the blood when swallowed than glutathione itself.