Veterinary anthelmintic reference · Animal use only
Levamisole, explained for the people who use it.
A clear, current reference on levamisole — a broad-spectrum dewormer for cattle, sheep, goats, pigs and poultry. Understand what it treats, work out an estimated dose, and learn the safety and withdrawal rules before you treat an animal.
Drug class
Imidazothiazole anthelmintic
Treats
Roundworms & lungworms
Typical rate
7.5–8 mg per kg body weight
Routes
Drench, injection, in water
Educational information only — not veterinary advice. This site does not diagnose, treat, cure or prevent any disease. Always confirm products, doses and withdrawal times with a licensed veterinarian and the manufacturer’s label before treating any animal.
Estimate a dose
Levamisole dosage calculator
Enter an animal’s weight and your product’s concentration to estimate the amount of levamisole to give. This is a starting point for a conversation with your vet — not a prescription.
How the estimate is built
Total dose (mg) = body weight in kg × dose rate (mg/kg). Volume (mL) = total dose ÷ product concentration (mg/mL). A 10% solution is 100 mg/mL, 20% is 200 mg/mL, and so on.
Concentration cheat sheet
Percent strength converts straight to mg/mL: 10% = 100 mg/mL, 13% = 130 mg/mL, 18.15% ≈ 181.5 mg/mL, 20% = 200 mg/mL. Soluble drench powders are reconstituted first — follow the mixing directions to get the right strength.
Before you treat, get the withdrawal time right
For any animal that produces meat, milk or eggs for people, you must observe the withdrawal period printed on the label. Extra-label use changes those times and, in the U.S., is only lawful under a veterinarian. When in doubt, ask before you dose.
The basics
What is levamisole?
Levamisole is a synthetic anthelmintic — a dewormer — in the imidazothiazole class. It has been used in veterinary medicine for decades to control internal roundworms in livestock. It works by overstimulating the parasite’s nervous system, which paralyses the worm so the animal can pass it.
It is valued for being fast-acting, broadly effective against gastrointestinal and lung roundworms, and inexpensive. It is not effective against tapeworms or flukes, and it does nothing for external parasites such as lice, mites or flies. Levamisole is sometimes sold as tetramisole, a related mixture, and appears under many generic brand names worldwide.
Because worm populations can develop resistance, levamisole is often rotated with dewormers from other chemical groups as part of a planned parasite-control programme. A veterinarian or a fecal egg count can tell you whether it is the right choice for your animals.
What it treats
Common uses in animals
Levamisole targets nematode (roundworm) infections. Below are the parasite groups it is generally used against — always confirm the labeled indications for your specific product and species.
Gastrointestinal roundworms
Stomach and intestinal worms such as Haemonchus, Ostertagia, Trichostrongylus, Cooperia and Nematodirus in ruminants.
Lungworms
Respiratory roundworms such as Dictyocaulus in cattle, sheep and goats, and Metastrongylus in pigs.
Pig & poultry roundworms
Ascaris suum and nodular worms in swine; Ascaridia and Capillaria in poultry, typically via medicated water.
Where a fresh group is needed
Used in rotation when worms have become resistant to other dewormer classes — guided by a fecal egg count and your vet.
A note on other uses. Levamisole has been studied as an immune-modulating agent in both animals and humans. Those uses are specialised, are outside the labeled deworming indications, and should only ever be considered under direct veterinary or medical supervision. This site covers its use as a dewormer in animals only.
By species
Dosing starts with the animal
Typical labeled dose rates differ by species and product. Use these as orientation, then confirm with the label and your veterinarian. Need products or a prescription? Each card links to the matching range at Vetr.
Cattle
≈ 8 mg/kg, single drench
Labeled for stomach worms, intestinal worms and lungworms in beef and non-lactating cattle.
Shop cattle range →Sheep
≈ 7.5–8 mg/kg, single dose
Widely used against Haemonchus and other strongyles; weigh the heaviest animals in the group.
Shop sheep range →Goats
Vet-directed (extra-label)
Not FDA-approved in goats; goats metabolise dewormers quickly, so dosing must be set by a vet.
Shop goat range →Pigs
≈ 8 mg/kg or in water
Controls large roundworm, nodular worm and lungworm; water-soluble products dose by tank volume.
Shop pig range →Poultry
Flock dose, in drinking water
Dosed for the whole flock through water for Ascaridia and Capillaria; follow the label rate.
Shop all products →Reference chart
Typical dosing by species
Orientation figures drawn from common product labels and veterinary literature. Products differ — your label always takes priority.
| Species | Typical rate | Usual route | Main targets |
|---|---|---|---|
| Cattle | 8 mg/kg | Oral drench (also injectable, pour-on, bolus) | Stomach, intestinal & lungworms |
| Sheep | 7.5–8 mg/kg | Oral drench | Haemonchus, strongyles, lungworm |
| Goats | Vet-directed* | Oral (extra-label) | Gastrointestinal roundworms |
| Pigs | ≈ 8 mg/kg | In feed/water or injectable | Ascaris suum, nodular & lungworms |
| Poultry | Per label | Medicated drinking water (flock) | Ascaridia, Capillaria |
*Levamisole is not FDA-approved in goats. Any use is extra-label and must be directed by a licensed veterinarian. Goats often require different dosing than sheep because they clear the drug faster.
Dose it accurately
Getting the amount right
Weigh, don’t guess
Under-dosing wastes product and drives resistance; over-dosing is dangerous. Use a scale, a weigh tape, or a load-bar system, and dose the group to the heaviest animals’ weight bands rather than a single flock average when animals vary a lot.
Measure the volume carefully
Use a calibrated drench gun or syringe and check it against a known volume before you start. Small errors on a concentrated product add up quickly across a herd.
Mix soluble powders exactly
Reconstitute soluble drench powders with the stated amount of water, mix thoroughly, and use within the storage window on the label. The final concentration — and therefore your mL figure — depends on mixing it correctly.
Record and observe withdrawal
Write down the date, product, dose and the animals treated, then respect the meat, milk and egg withdrawal periods before those products enter the food chain.
Use it responsibly
Safety & side effects
Levamisole is effective and widely used, but it has a narrow margin of safety. Knowing the warning signs, the cautions and the withdrawal rules is the difference between a routine treatment and an emergency.
A narrow margin of safety
With many dewormers you can dose a little high without much consequence. Levamisole is not like that: the effective dose sits relatively close to the dose that causes toxic effects. That is why weighing animals, measuring carefully and following the label matter more here than with almost any other wormer.
Signs of trouble come from the same mechanism that kills the worm. Levamisole stimulates nicotinic receptors, so an overdose produces cholinergic effects in the treated animal.
Overdose warning signs
Usually appear within minutes to a couple of hours of dosing.
- Excess salivation or drooling
- Muscle tremors or twitching
- Restlessness, head shaking, agitation
- Increased urination or defecation
- Rapid or laboured breathing
- Collapse in severe cases
What to do: stop dosing, remove other animals from the same batch if a mixing error is suspected, and call your veterinarian right away.
Know the limits
Cautions & interactions
Species cautions
Best established in cattle, sheep, pigs and poultry. It is generally avoided in horses, used only with veterinary direction in goats (not FDA-approved), and used cautiously, if at all, in dogs and cats because of the narrow safety margin.
Do not combine with organophosphates
Using levamisole alongside organophosphate parasiticides or other cholinergic agents can stack effects and raise the risk of toxicity. Separate treatments and check with your vet.
Stressed & sick animals
Debilitated, heavily parasitised, or severely stressed animals may tolerate treatment less well. A vet can advise on timing and supportive care.
Pregnancy & young stock
Follow label guidance for breeding, pregnant and very young animals; where the label is silent, treat only under veterinary direction.
Human handling
Wear gloves, avoid skin contact and inhalation, don’t eat or smoke while dosing, and wash afterwards. Keep the product away from children and pets.
Resistance
Under-dosing and over-frequent use drive resistance. Use fecal egg counts, dose to weight, and rotate chemical groups as your vet advises.
Protect the food supply
Withdrawal times
If a treated animal produces meat, milk or eggs for people, you must wait the labeled withdrawal period before those products enter the food chain. Times vary by product, formulation and country — the values below are illustrative, not a substitute for your label.
| Product type | What to check |
|---|---|
| Meat (any species) | A defined number of days between treatment and slaughter — commonly several days to over a week depending on formulation. |
| Milk | Many levamisole products are not permitted in animals producing milk for human consumption. Check the label before use in dairy animals. |
| Eggs | Water-medicated poultry products carry their own egg withdrawal — often several days. Do not use in laying birds unless the label allows it. |
Extra-label use changes everything
Using a product differently from its label — a different species, dose, route or a shortened interval — can extend withdrawal times well beyond the printed figure. In the U.S., extra-label drug use is only lawful when a licensed veterinarian directs it within a valid veterinarian-client-patient relationship and assigns an appropriate withdrawal time. When you’re outside the label, you need a vet.
Questions, answered
Frequently asked questions
Straight answers to the questions people ask most about using levamisole in animals. When in doubt, the safest next step is always a conversation with your veterinarian.
What is levamisole used for in animals?
Levamisole is a broad-spectrum dewormer used to control roundworms — including gastrointestinal and lung roundworms — in cattle, sheep, goats, pigs and poultry. It does not treat tapeworms, flukes, or external parasites such as lice and mites.
What is the usual levamisole dose?
Most ruminant labels use about 7.5–8 mg per kg of body weight as a single dose. The exact figure, concentration and route vary by product, so confirm against the label and your vet. The dosage calculator above gives a quick estimate — because the margin of safety is narrow, weigh animals rather than guessing.
Is levamisole safe for goats?
Levamisole is not FDA-approved in goats, and goats clear many dewormers faster than sheep, so dosing differs. Any use in goats is extra-label and should be directed by a licensed veterinarian who can set the dose and the withdrawal time.
Can I give levamisole to horses, dogs or cats?
It is generally avoided in horses and used only cautiously, if at all, in dogs and cats, because of the narrow margin of safety. Consider these uses only under direct veterinary supervision.
What are the signs of an overdose?
Overdose produces cholinergic effects — excess salivation, muscle tremors, restlessness, increased urination or defecation, and laboured breathing — usually within minutes to a couple of hours. Stop dosing and call your veterinarian immediately. See the safety section for detail.
How long is the withdrawal time?
It varies by product and is printed on the label. Meat withdrawals commonly run from several days to over a week; many products are not permitted in dairy animals producing milk for people; and poultry water products carry their own egg withdrawal. Extra-label use can extend these times and requires a vet to assign them.
Does levamisole kill tapeworms or flukes?
No — it works on roundworms only. Tapeworms, liver flukes and external parasites need a different class of product.
Can worms become resistant to it?
Yes. Under-dosing and over-frequent use drive resistance. Dose to weight, use fecal egg counts, and rotate dewormer groups on veterinary advice to keep it working.
Do I need a prescription?
Availability and prescription status vary by country and product. When a treatment falls outside the label, or you’re unsure, a licensed veterinarian can advise and provide a prescription where required. Vetr offers care and prescription support across the U.S.
Not sure what your animal needs?
Talk to a licensed vet before you treat.
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