Yes, you can overdose on ivermectin, and doing so can cause serious harm including seizures, dangerously low blood pressure, coma, and in severe cases, death. The FDA has confirmed receiving multiple reports of people requiring hospitalization after taking ivermectin inappropriately, particularly from animal-grade formulations.
How Ivermectin Works at Normal Doses
Ivermectin is an antiparasitic drug approved for humans at very specific, weight-based doses. For treating intestinal roundworm infections, the standard dose is about 200 micrograms per kilogram of body weight, taken once. For river blindness, it’s about 150 micrograms per kilogram. To put that in perspective, a 180-pound person would take roughly 16 milligrams total, a small amount of active ingredient.
At these doses, ivermectin stays largely outside the brain. Your body has a transport protein that acts like a bouncer at the blood-brain barrier, actively pumping ivermectin back out before it can accumulate in the central nervous system. This is a critical safety feature, because ivermectin’s mechanism of action, enhancing the activity of a calming brain chemical called GABA, could cause serious neurological problems if too much of the drug reaches brain tissue.
What Happens During an Overdose
When someone takes significantly more ivermectin than prescribed, the transport system that protects the brain gets overwhelmed. The drug crosses into the central nervous system in higher concentrations and begins amplifying GABA signaling beyond safe levels. This is what drives the most dangerous overdose symptoms.
Overdose effects fall into two categories. The milder, non-neurological symptoms include nausea, vomiting, diarrhea, dizziness, itching, muscle pain, and skin reactions. These can occur even at doses that aren’t life-threatening, but they signal the body is handling more drug than it should.
The neurological symptoms are far more concerning:
- Lethargy and confusion, progressing to stupor
- Loss of balance and coordination (ataxia)
- Tremors and seizures
- Drooling and disorientation
- Coma, in severe cases
Low blood pressure is another serious risk. A letter published in the New England Journal of Medicine documented cases where patients developed confusion, ataxia, weakness, dangerously low blood pressure, and seizures after taking ivermectin outside of prescribed guidelines. Most people who didn’t require hospital admission still experienced gastrointestinal distress, dizziness, confusion, vision problems, or rash.
Why Veterinary Products Are Especially Dangerous
The active ingredient in ivermectin is chemically the same whether it’s in a human tablet or a horse dewormer. The critical difference is concentration and dosing. Animal formulations, particularly the concentrated paste used for horses, come in dramatically larger doses designed for animals weighing 1,000 pounds or more. A single tube of horse paste can contain enough ivermectin for multiple human overdoses.
These products also use different inactive ingredients and delivery systems that have never been tested for safety in humans. The FDA has specifically warned against using animal ivermectin products, noting that multiple people have required medical attention, including hospitalization, after self-medicating with livestock formulations.
Genetic Factors That Increase Risk
Some people are at much higher risk of toxicity than others, even at standard doses. The transport protein that keeps ivermectin out of the brain is encoded by a gene called ABCB1. People with mutations in this gene have a weakened version of that protective barrier. In these individuals, even a normal therapeutic dose of ivermectin can cause severe neurological symptoms including coma, loss of coordination, double vision, and abnormal reflexes.
Most people don’t know whether they carry this mutation, which makes taking ivermectin without medical guidance an unpredictable gamble. There’s no simple way to tell in advance how efficiently your body will keep the drug out of your brain.
Drug Interactions That Raise Toxicity Risk
Certain medications use the same transport protein that protects your brain from ivermectin. If you’re taking one of these drugs, it can compete with ivermectin for that protective pump, letting more ivermectin accumulate in the central nervous system. Cyclosporine, an immune-suppressing drug used after organ transplants, has been shown in animal studies to increase ivermectin concentrations in the brain and worsen neurotoxicity. HIV protease inhibitors pose a similar theoretical risk. Anyone taking medications that affect this transport system faces a higher chance of serious side effects, even from doses that would normally be safe.
What Treatment Looks Like
There is no antidote for ivermectin overdose. Treatment is entirely supportive, meaning doctors manage each symptom as it appears: IV fluids for low blood pressure, anti-seizure interventions if needed, monitoring of breathing and consciousness. Recovery depends on how much was taken and how quickly the person receives care. Mild overdoses with mainly gastrointestinal symptoms typically resolve within a day or two. Severe neurological toxicity, particularly cases involving coma or repeated seizures, can require intensive hospital care and carries a real risk of lasting harm or death.
If you suspect someone has taken too much ivermectin, calling Poison Control (1-800-222-1222 in the U.S.) or going to an emergency room immediately gives the best chance of a safe outcome. The earlier treatment begins, the better the prognosis for serious exposures.