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Short answer: ivermectin reaches its highest level in the blood about 4 hours after a dose, and its plasma half-life is about 18 hours. Most of it has left the bloodstream within a few days, but it's excreted slowly, mainly in stool, over roughly 12 days. The figures below come from the FDA prescribing information for Stromectol.
Key numbers
| Measure | What the label reports |
|---|---|
| Time to peak blood level | About 4 hours after an oral dose |
| Plasma half-life | About 18 hours |
| Where it's processed | The liver, mainly by the enzyme CYP3A4 |
| How it leaves the body | Almost entirely in stool, over about 12 days |
| Amount in urine | Less than 1% |
What half-life means here
Half-life is the time it takes for the amount in your blood to fall by half. After one half-life (about 18 hours) roughly half is left; after about five half-lives, around four days, the level in the blood is very low. That's a rule of thumb, not a precise clock, because ivermectin is fat-soluble and some is stored in fat and the liver, then released slowly. That's part of why traces leave the body over more than a week.
What can change how long it lasts
- Liver function. Ivermectin is broken down in the liver, so liver disease can slow clearance. Tell your prescriber if you have it.
- Other medicines. Drugs that block CYP3A4 or the P-glycoprotein transporter can raise ivermectin levels. Ivermectin can also increase the effect of warfarin. Our side effects and interactions guide lists the main ones.
- Food. The label notes that a high-fat meal raises how much ivermectin is absorbed, which is why it's usually taken on an empty stomach with water.
- Body composition. Because it's stored in fat, levels can behave differently from person to person.
Will it show up on a drug test?
Ivermectin isn't one of the substances standard workplace drug panels look for, and it isn't known to cause false positives on them. If you're asked, tell the testing lab what medicines you take.
When to get help
Side effects usually appear within the first day or two, while levels are highest. Dizziness, nausea, diarrhea and itching are the most common. Confusion, a severe rash, trouble walking, seizures or fainting are signs to stop and get medical help right away, as are any signs of an overdose. Veterinary ivermectin has caused serious poisonings in people for exactly this reason; here's why not to use it.
How much to take, and how often, is your prescriber's decision. We don't give dosing instructions; how the ivermectin dose is decided explains what they weigh up.
Sources
Figures are from the FDA-approved prescribing information for Stromectol (ivermectin) tablets, Merck, and MedlinePlus.
The short version
Ivermectin peaks about 4 hours after a dose, has a half-life of about 18 hours, and is cleared mostly through stool over roughly 12 days. Liver disease and some medicines can make it last longer.
Frequently asked questions
How long does ivermectin stay in your system?
Its plasma half-life is about 18 hours, so blood levels are low after around four days, but it is excreted slowly in stool over about 12 days.
When does ivermectin peak in the blood?
About 4 hours after an oral dose, according to the FDA label for Stromectol.
How is ivermectin removed from the body?
It's broken down in the liver, mainly by CYP3A4, and leaves almost entirely in stool. Less than 1% leaves in urine.
Does ivermectin show up on a drug test?
It isn't part of standard workplace drug panels and isn't known to cause false positives on them.
This article is general information, not medical advice. Oral ivermectin is a prescription medicine under US federal law, and only some states let pharmacists dispense it without an individual prescription. Talk to your doctor or pharmacist before using it.
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