NAC (N-acetyl cysteine) is one of the antioxidants people add when they start reading fertility papers — and one of the easiest to mis-dose. PCOS research often uses 600–1,200 mg a day. Some preconception formulas print 400 mg. Those are food-supplement amounts, not an inositol replacement.
The preconception vitamins that apply to everyone remain folic acid 400 µg and vitamin D. NAC is not on that list. A Cochrane review of vitamins and minerals for subfertility in women is why antioxidants show up in fertility papers.
What NAC is
N-acetyl cysteine is a stable way of giving cysteine, which the body uses to make glutathione, a major antioxidant. Fertility interest sits in two piles: oxidative stress (eggs, sperm, reproductive tissue) and metabolic/PCOS literature where NAC has been studied as an adjunct, often at higher doses than you will find in a conception multi.
Dose honesty: 50 mg vs 400 mg vs 600–1,200 mg
A token 50–100 mg line on a multi is a small extra. 400 mg is a working food-supplement amount — still below many PCOS papers. Standalone NAC is often 600 mg, and literature doses of 600–1,200 mg are a clinician conversation, not something to invent by stacking bottles. Brands also print L-cysteine or N-acetyl L-carnitine, which are not the same line item as NAC. Confirm milligrams on the pack you buy.
PCOS, inositol, and the mix-up
UK shoppers who type “PCOS supplements” are usually sent toward myo-inositol in gram doses (often around 4 g), sometimes with D-chiro-inositol, plus dietetic care. NAC appears in PCOS literature as a separate antioxidant/metabolic adjunct, typically at 600–1,200 mg — not as stealth inositol. A 400 mg line in a multi is a contribution at most. Do not drop prescribed care because a 21-ingredient formula felt complete. See PCOS, diet, vitamin D and inositol.
IVF and NAC
Some IVF patients add NAC because they have read about oxidative stress. Do not add a standalone 600 mg NAC on top of a formula that already contains hundreds of milligrams unless a clinician asked. Show the label at the nurse appointment. Stop at a positive test. Timing: IVF supplement protocol, 90 days before retrieval.
People report gastrointestinal upset with standalone NAC, especially on an empty stomach. Take food-supplement doses with a meal. If you take prescription drugs, ask a pharmacist. Opened NAC bottles also have a sulphur smell; that is the compound, not automatically a spoiled tub.
How Her Fertility fits
Her Fertility includes NAC at 400 mg in the daily serving, alongside CoQ10 300 mg, 5-MTHF 400 µg, zinc 20 mg and selenium 200 µg. That 400 mg is the amount this article is named for. It is not a 600–1,200 mg PCOS literature protocol, and Her Fertility is not an inositol product. Do not stack extra NAC on top unless a clinician designed the total.
FAQ
Is 400 mg NAC enough for PCOS?
Often, no — not if you are trying to match literature doses of 600–1,200 mg, and not if the actual gap is inositol in grams. Speak to a GP or specialist.
Can I add extra NAC to reach 1,200 mg?
Only if a qualified clinician designed that total and has seen what is already in any all-in-one you take.
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