Nystatin: what it treats, how to take it, side effects
Last updated September 3, 2026.
Nystatin is an antifungal - it stops the growth of the yeast that causes thrush. It has been doing this one job since the 1950s, and it barely absorbs into the body at all, which is exactly why it is so gentle: it works where you put it.
What does it treat?
Fungal infections of the inside of the mouth - oral thrush, the white patches of candida - and of the lining of the stomach and intestines. The label's indication is candidiasis of the oral cavity. Thrush shows up after antibiotics, with inhaled steroids, with dentures, and when immunity is lowered.
How do you take it?
Two forms. The suspension, for mouth infections: usually four times a day - shake it well, then place half the dose in each side of the mouth and hold it there as long as you can before swallowing. The contact time is the treatment, so the holding matters more than the swallowing. The tablets, for stomach and intestinal infections: usually three times a day. Use it for exactly as long as prescribed, even when the white patches clear early - stopping too soon lets the yeast regrow. Missed dose: take it when you remember unless the next one is close; never double up.
Side effects to know
- Common: diarrhea, nausea, and stomach bloating or pain.
- Serious - stop and call your doctor immediately: irritation or burning of the mouth, hives, rash or itching, and difficulty breathing or swallowing.
Who should not take it?
Very few people - allergy to nystatin or its ingredients is the main stop sign. One formulation note: the suspension is sweetened with sucrose (about a third by weight) and contains a trace of alcohol, so diabetes and sugar-restricted diets go on the list for your doctor. If you become pregnant, call your doctor. And it is worth knowing why the safety profile is so mild: the label notes gastrointestinal absorption is insignificant - the drug passes through you largely unchanged.
When is it an emergency?
Difficulty breathing or swallowing is a 911 call. For an overdose, call Poison Control at 1-800-222-1222. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
Why do I have to hold nystatin in my mouth instead of just swallowing it?
Because it works by contact, not by absorption. MedlinePlus instructs placing half the dose in each side of the mouth and holding it as long as possible before swallowing - and the label notes the drug barely absorbs into the bloodstream at all. It kills the yeast it touches, so the longer it touches, the better it works.
Why did I get thrush after my antibiotics?
Antibiotics clear bacteria, including the harmless ones that keep candida yeast in check - and yeast fills the vacancy. Thrush also follows inhaled steroid use, dentures, and lowered immunity. MedlinePlus is direct that nystatin treats the fungal infection itself; if thrush keeps coming back, your doctor looks for the reason underneath.
Is the nystatin liquid a problem if I have diabetes?
Worth mentioning to your doctor. The label lists sucrose at about 33.5% of the suspension, plus a trace of alcohol. Four doses a day is real sugar. Your prescriber weighs it against the benefit, and blood-sugar monitoring does the rest.
Can I stop the nystatin once the white patches are gone?
No. MedlinePlus says to use it as long as instructed even if you feel better - stopping too soon or skipping doses can leave the infection incompletely treated. Visible clearing means the yeast is losing, not that it is gone. And if symptoms are still there after you finish, call your doctor.
Can I drink alcohol while using nystatin?
Neither the label nor MedlinePlus gives nystatin-specific alcohol language - the drug barely enters your bloodstream, which is why the interaction list is nearly empty. A drink is unlikely to matter here; if you are treating an intestinal infection, your stomach will still thank you for going light.
What happens if I miss a dose of nystatin?
Take it as soon as you remember, unless it is almost time for the next one - then skip it and never double up. Four times a day is a rhythm: after meals and before bed covers it without a spreadsheet.