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Amino acids & precursors · side effects reported by users

NAC Side Effects: What Reddit Users Report

About this entry (NAC (N-acetylcysteine)): N-acetylcysteine, discussed for rumination, OCD-type thoughts and compulsive habits.

40 of 127 Reddit owner comments about NAC (31%) describe an unwanted effect. These are self-reports from Reddit anxiety, stress and supplement communities (May 2026 to October 2026), not a measured side-effect rate, and many people report no problems at all.

NAC (N-acetylcysteine) overall: 3.2 · tolerability 3.2 (higher means fewer unwanted-effect reports).

Most common complaints

Side effects: 39 owner comments
Mood: 24 owner comments
Feeling flat or numb: 23 owner comments

Safety notes from NIH and published research

In clinical trials the most common side effects were gastrointestinal, such as nausea and upset stomach.^[PubMed]

Stop and talk to a doctor if an effect is severe or does not settle. Ask a pharmacist about interactions with any medicine you take.

In their words

2/5 Feeling flat or numbMood
“I posted a thread where I said NAC gave me anhedonia and I took it for less than a month.”

owner comment via r/Supplements · 2026-06-02 · 19 upvotes

2/5 Feeling flat or numbMood
“NAC gave me mad anhedonia I couldn't even recognize myself.”

owner comment via r/Nootropics · 2026-10-24 · 17 upvotes

3/5 Feeling flat or numbMood
“I used to experience this type of anhedonia from NAC for a while when I took 600 mg every day (Doctor's Best, a pretty strong supplement with molybdenum and selen).”

owner comment via r/Supplements · 2026-05-11 · 10 upvotes

2/5 Feeling flat or numbMood
“I bought NAC and it's not fast acting and I have to take it for weeks just so it can give me anhedonia.”

owner comment via r/Nootropics · 2026-06-25 · 8 upvotes

2/5 Feeling flat or numbMood
“NAC is the shit. It did feel like it could give me some slight anhedonia when I first started taking it, but I don't take it everyday now. It's honestly one of my favs before the gym”

owner comment via r/Supplements · 2026-09-01 · 8 upvotes

3/5 Feeling flat or numbMood
“Turns out all signs point to the long-term NAC use from my understanding (albeit the long period of Accutane probably had some mild effect on me as well).”

owner comment via r/Nootropics · 2026-05-06 · 2 upvotes

1/5 Side effects
“Anecdotal but NAC made my anxiety worse”

owner comment via r/Nootropics · 2026-10-17 · 5 upvotes

1/5 Feeling flat or numbMood
“This is so interesting because I have terrible anhedonia the past few months and have been taking 600-1200mg NAC 5-7xweek for nearly a year.”

owner comment via r/Supplements · 2026-05-12 · 4 upvotes

Frequently asked

What side effects do people report with NAC?

40 of 127 Reddit owner comments about NAC (31%) describe an unwanted effect. These are self-reports, not a measured side-effect rate.

Is NAC safe?

Safety depends on your health and medicines. The NIH and other sources listed on this page note specific cautions. Ask a doctor or pharmacist before starting, especially if you take other medicines or are pregnant.

More on NAC

Compare side-effect reports: NAC (N-acetylcysteine) vs Inositol · NAC (N-acetylcysteine) vs L-theanine