What Is Ivermectin? Uses, Dosage, and Safety Guide
Updated: Aug 21
Written by Dr. Charles Drew, Lead Pharmaceutical Content Specialist & Clinical Drug Information Reviewer
Reviewed for medical accuracy under the Ivermectinkart Editorial Polic
Introduction
Ivermectin is a prescription antiparasitic medicine used to treat certain infections caused by worms and other parasites. In the United States, oral ivermectin tablets are FDA-approved for intestinal strongyloidiasis and onchocerciasis, while topical ivermectin products have separate approved uses, including conditions such as head lice and rosacea. A safe ivermectin dosage depends on the condition being treated, body weight, formulation, and individual health factors, so there is no universal dose for every infection. Ivermectin is also used off-label for some conditions, including scabies, when a clinician considers it appropriate. Although the medicine has legitimate medical uses, taking veterinary products, excessive amounts, or using it without proper medical guidance can cause serious harm. This guide explains what ivermectin is, how it works, its approved and off-label uses, general dosage information, side effects, precautions, and situations that require medical attention.
What Is Ivermectin and How Does It Work?
Ivermectin is an antiparasitic medicine from a drug group called avermectins. It interferes with specific chloride channels in susceptible parasites, disrupting their nerve and muscle function and ultimately causing paralysis or death of the parasite.
These particular channels are found in many invertebrates but not in the same form in humans. At recommended therapeutic doses, ivermectin also does not readily cross the human blood-brain barrier.
The exact effect depends on the parasite. For example, ivermectin acts against intestinal stages of Strongyloides stercoralis. In onchocerciasis, it acts against the microscopic larvae, called microfilariae, but does not kill the adult Onchocerca volvulus worms.
Ivermectin is not a general-purpose medicine for infections. It works against specific susceptible parasites, and the formulation, dose, and treatment schedule must match the condition being treated.
What Is Ivermectin Used For?
In the United States, oral ivermectin tablets are FDA-approved for intestinal strongyloidiasis and onchocerciasis. Clinicians may also prescribe ivermectin for certain other parasitic conditions when supported by clinical guidance, but these uses may be off-label rather than FDA-approved.
Strongyloidiasis
Strongyloidiasis is caused by the roundworm Strongyloides stercoralis. The infection can persist for years and may become dangerous in people whose immune systems are significantly suppressed.
The CDC clinical guidance for Strongyloides treatment identifies oral ivermectin as first-line therapy for acute and chronic strongyloidiasis. Follow-up testing can be important in people with persistent symptoms or evidence of continuing infection.
Onchocerciasis
Onchocerciasis, sometimes called river blindness, is caused by Onchocerca volvulus. Ivermectin lowers the number of microfilariae, the larval form responsible for much of the disease burden, but it does not kill the adult worms.
Because adult parasites can continue producing microfilariae, retreatment may be necessary under an appropriate treatment program.
Scabies
Oral ivermectin may be used to treat scabies, but this is an off-label use in the United States. The FDA has not approved oral ivermectin tablets specifically for scabies.
CDC guidance states that oral ivermectin and topical permethrin have similar efficacy for classic scabies. Treatment selection depends on factors such as pregnancy, body weight, drug interactions, severity, and whether topical treatment is practical.
Head lice and other uses
Topical ivermectin lotion has an FDA-approved role in treating head lice in appropriate patients. Oral ivermectin has also been used for head lice in some circumstances, but that oral use is not FDA-approved for lice.
Ivermectin may appear in treatment guidance for several other parasitic diseases. That does not mean the same dosing schedule should be reused across conditions.
TABLE 1
Condition | Ivermectin use | U.S. status |
Intestinal strongyloidiasis | Oral tablets | FDA-approved |
Onchocerciasis | Oral tablets | FDA-approved |
Classic scabies | Oral treatment may be used | Off-label |
Crusted scabies | Oral ivermectin may be combined with topical treatment | Off-label |
Head lice | Topical ivermectin lotion | FDA-approved topical use |
Rosacea | Certain topical formulations | FDA-approved topical use |
COVID-19 | Prevention or treatment | Not FDA-approved or authorized |
Regulatory status varies by formulation and country. A product approved for one condition, route, or species should not be assumed appropriate for another.
What Is the Usual Ivermectin Dosage?
Ivermectin dosage is usually based on body weight and the condition being treated. The following amounts summarize U.S. labeling and CDC clinical guidance for general education only; they are not instructions for self-treatment.
For FDA-approved oral tablet use, current U.S. labeling recommends approximately 200 micrograms per kilogram (mcg/kg) as a single oral dose for intestinal strongyloidiasis and approximately 150 mcg/kg as a single oral dose for onchocerciasis. The product label instructs patients to take oral tablets on an empty stomach with water.
CDC recommendations may differ for specific clinical circumstances. For example, CDC guidance for uncomplicated strongyloidiasis lists ivermectin 200 mcg/kg orally for one to two days.
Why are ivermectin doses different for different conditions?
Different parasites have different life cycles, susceptibility patterns, and treatment requirements. Some conditions may need only one dose, while others require repeated treatment or follow-up testing.
Scabies illustrates this difference. CDC guidance for classic scabies describes two oral ivermectin doses of 200 mcg/kg, usually separated by 7 to 14 days, because ivermectin has limited activity against mite eggs. This remains an off-label oral use in the United States.
TABLE 2
Condition | General adult/pediatric weight-based regimen in cited guidance | Important context |
Intestinal strongyloidiasis | About 200 mcg/kg orally | FDA-approved oral use; labeling describes a single dose |
Onchocerciasis | About 150 mcg/kg orally | FDA-approved oral use; retreatment may be required |
Classic scabies | 200 mcg/kg orally, repeated after 7–14 days | Off-label oral use in the U.S. |
Crusted scabies | 200 mcg/kg on multiple treatment days plus topical therapy | Off-label; specialist-directed treatment |
Disseminated/hyperinfection strongyloidiasis | 200 mcg/kg daily until parasitological clearance criteria are met | Severe disease requiring medical management |
These are guideline or labeling examples, not personalized dosing instructions. Pregnancy, body weight, suspected Loa loa infection, immune status, drug interactions, and the exact diagnosis can change whether ivermectin is appropriate.
What Side Effects Can Ivermectin Cause?
Ivermectin can cause gastrointestinal, neurological, and skin-related side effects, although the pattern varies with the condition being treated. Some reactions may come from the body's response to dying parasites rather than from the medicine alone.
Reported side effects of oral ivermectin include:
dizziness
nausea
vomiting
diarrhea or constipation
abdominal discomfort
reduced appetite
tiredness or weakness
itching
rash or hives
sleepiness or tremor
The current U.S. ivermectin prescribing information also describes uncommon but potentially serious neurological reactions, including confusion, altered consciousness, seizures, and coma.
Why can onchocerciasis treatment cause stronger reactions?
When ivermectin kills large numbers of microfilariae, an inflammatory response called a Mazzotti-type reaction may occur. Symptoms can include itching, rash, swelling, fever, joint discomfort, and swollen or tender lymph nodes.
These reactions need to be distinguished from an allergic reaction or other serious medical complication, particularly if symptoms are severe.
Who Should Be Especially Careful With Ivermectin?
Ivermectin requires extra caution in pregnancy, breastfeeding, young children, people taking certain medicines, and people who may have been exposed to Loa loa. The balance of benefit and risk should be assessed by a health professional.
Pregnancy and breastfeeding
Current U.S. oral-tablet labeling states that adequate, well-controlled studies in pregnant women are lacking and that safety in pregnancy has not been established. Ivermectin is also present in human breast milk at low concentrations.
CDC guidance similarly treats pregnancy and lactation as important considerations when ivermectin is being considered for strongyloidiasis. The risk of untreated infection may sometimes also be significant, so decisions need to be individualized.
Children under 15 kg
U.S. oral-tablet labeling states that safety and effectiveness have not been established in children weighing less than 15 kg. CDC guidance also lists this weight group as an important precaution for strongyloidiasis treatment.
Exposure to Loa loa
People who have lived in or spent substantial time in areas of West or Central Africa where Loa loa is endemic may need assessment before ivermectin treatment. People with very high Loa loa parasite levels can rarely develop severe encephalopathy after microfilaricidal treatment.
Tell your clinician about relevant travel and residence history rather than treating presumed parasite infections yourself.
Medication interactions
Give your prescriber or pharmacist a complete list of prescription medicines, over-the-counter drugs, and supplements.
The U.S. label reports rare increases in INR, a blood-clotting measurement, when ivermectin has been given with warfarin.
Is Ivermectin Approved for COVID-19?
No. The FDA has not approved or authorized ivermectin for preventing or treating COVID-19 in humans. The agency states that currently available clinical-trial data do not demonstrate that ivermectin is effective for COVID-19.
The FDA's ivermectin and COVID-19 guidance also warns that high doses can be dangerous and that veterinary ivermectin products should never be used by humans.
Veterinary formulations may contain different concentrations or inactive ingredients and are designed for animal species rather than people. FDA reports have included patients requiring medical attention and hospitalization after self-medicating with animal ivermectin.
A laboratory finding that a substance affects a virus in a test tube does not establish that it safely treats that infection in people. Human treatment decisions require appropriate clinical evidence, dosing studies, and regulatory review.
When Should You Seek Medical Care?
Seek urgent medical attention after ivermectin if you develop severe confusion, marked drowsiness or loss of consciousness, seizures, difficulty breathing, severe weakness, significant problems with balance or walking, or signs of a serious allergic reaction.
An overdose can cause nausea, vomiting, diarrhea, low blood pressure, dizziness, coordination problems, seizures, coma, and potentially death. The FDA specifically warns that taking large doses can be dangerous.
You should also contact a health professional if symptoms of the original infection persist after treatment, because some parasitic diseases require follow-up testing or repeat therapy. Strongyloidiasis, for example, may require stool examinations to confirm clearance.
Never take ivermectin intended for horses, cattle, or other animals. Use only a human product obtained from a legitimate source and prescribed or recommended appropriately for the condition being treated.
Conclusion
Ivermectin is a well-established antiparasitic medicine with specific human medical uses, including FDA-approved oral treatment for intestinal strongyloidiasis and onchocerciasis. An ivermectin dosage is not interchangeable between conditions: the correct amount, timing, formulation, and follow-up depend on the diagnosis, body weight, and individual risk factors. Oral ivermectin may also be used off-label for conditions such as scabies under medical supervision.
Avoid self-treatment, high doses, and veterinary ivermectin products. If you think you have a parasitic infection or have questions about an ivermectin prescription, speak with a clinician or pharmacist who can confirm the diagnosis, appropriate formulation, and safe treatment plan.
Frequently Asked Questions
1. What parasites does ivermectin treat in humans?
Ivermectin treats several susceptible parasites, but its approved uses depend on formulation and country. In the United States, oral tablets are FDA-approved for intestinal strongyloidiasis and onchocerciasis. Clinicians may use it off-label for certain other parasitic conditions when clinically appropriate.
2. Can ivermectin be taken without a prescription?
Oral ivermectin for human use is a prescription medicine in the United States. It should be used for a confirmed or appropriately suspected condition under professional guidance. Buying unapproved products or taking veterinary ivermectin can expose you to incorrect concentrations, ingredients, and serious safety risks.
3. Should ivermectin be taken with food or on an empty stomach?
For FDA-approved oral tablet indications, U.S. labeling instructs patients to take ivermectin on an empty stomach with water. Some off-label protocols differ; CDC scabies guidance, for example, recommends taking oral ivermectin with food. Follow the directions given for your specific condition.
4. How long does ivermectin stay in the body?
The U.S. prescribing information reports an ivermectin plasma half-life of about 18 hours after oral administration. Ivermectin and its metabolites are eliminated mainly through the feces over several days. Drug elimination time does not determine how long treatment effects last against a particular parasite.
5. Can ivermectin be used during pregnancy?
Safety during pregnancy has not been adequately established, so ivermectin should not be taken during pregnancy without careful medical assessment. Treatment decisions depend on the infection and the risks of leaving it untreated. Tell your prescriber if you are pregnant, planning pregnancy, or breastfeeding.
6. Is ivermectin safe for children?
Ivermectin is used in children in certain circumstances, but weight and indication matter. U.S. oral-tablet labeling states that safety and effectiveness have not been established for children weighing under 15 kg. A pediatric clinician should determine whether ivermectin is appropriate and calculate any required dose.
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