Giving the wrong antibiotic dose can make your dog sicker or cause long-term problems. Metronidazole is useful for certain bacterial and protozoal infections, and for some cases of diarrhea, but the safe dose depends on your dog’s weight, the condition being treated, and other meds your dog takes.
Dosing is always weight-based. A common practical range used by vets is about 7.5–15 mg per kg of body weight given twice daily (every 12 hours). For protozoal infections like Giardia, many vets use 10–20 mg/kg twice daily for 5–7 days. Some anaerobic infections may need doses toward the higher end of those ranges. Never guess—use your dog’s exact weight and follow your vet’s instructions.
Quick examples: a 10 kg dog at 15 mg/kg gets 150 mg per dose (often given twice daily). A 5 kg dog at 10 mg/kg gets 50 mg per dose. Human tablets often come in 250 mg or 500 mg strengths, so vets may prescribe a compounded strength for small dogs or adjust the dose carefully.
Common side effects: nausea, vomiting, diarrhea, drooling, and reduced appetite. More serious problems include wobbliness, disorientation, or seizures—especially if your dog already has seizure disease. Long or very high-dose use can cause nerve problems (peripheral neuropathy) or liver stress. If you see any neurological signs, stop the medication and call your vet right away.
Interactions: Metronidazole is processed by the liver, so it can interact with other drugs the liver handles. If your dog takes anticonvulsants or multiple long-term meds, check with your vet—metronidazole can affect seizure threshold and may change how other drugs work.
Resist the urge to use leftover human meds. Misusing antibiotics promotes antimicrobial resistance and can delay correct treatment. If a vet prescribes metronidazole, finish the course unless the vet tells you otherwise.
Practical tips: weigh your dog on a reliable scale before dosing, give the medication with a small amount of food to cut down on stomach upset, and use a pill syringe or hide the pill in a soft treat if needed. Keep clear records of dose, time, and any side effects so you can report them to your vet.
When to call the vet: persistent vomiting, bloody stool, pale gums, sudden weakness, collapse, seizures, or any new odd behavior. Also call if you accidentally gave a much larger dose than prescribed. Your vet may advise monitoring, supportive care, or stopping the drug.
Bottom line: metronidazole can help, but dose carefully. Use mg/kg math, follow the vet’s plan, watch for side effects, and never give human meds without direction. If you’re unsure about dosing or your dog’s response, make the call to your vet.
