Also sold as Microzide, HCTZ, Hydrodiuril, found in Zestoretic, Lopressor HCT, Diovan HCT
Vets prescribe this for dogs, so being on it is not a problem in itself. This page is about what happens when a dog gets more than it was meant to have.
Hydrochlorothiazide is a diuretic with veterinary uses. An excessive amount causes dehydration and electrolyte disturbance. The common trap is that it is hidden inside many combination blood-pressure tablets.
Source-backed guidance. Not individualized veterinary advice.(more)
Compiled from veterinary poison-control and medical references, including the ASPCA Animal Poison Control Center, Pet Poison Helpline, and Merck Veterinary Manual.
Part of Heart and blood-pressure medication on our medication safety hub.
Call the practice that prescribed it: they know the dose your dog is on, which is what decides whether this matters. Out of hours, either line below is open.
Available 24/7. A consultation fee may apply.
Exposure details to have ready
These are the questions a veterinarian or poison-control operator will ask. Fill in what you know and leave the rest blank. This tool does not estimate a dose or a risk score: medication risk depends on the exact ingredient, strength, and formulation, so the assessment has to come from the clinician on the call.
- Keep the package, blister pack, or prescription bottle. The strength and the full ingredient list are what make the advice specific.
- Do not induce vomiting unless a veterinarian or poison-control professional tells you to. It is the wrong move for several medications and can cause harm on its own.
- Do not give milk, food, salt, hydrogen peroxide, or any home remedy on your own.
- Do not give a second dose of anything to make up for one you think was missed.
- Count what is left in the packet, so the number missing can be worked out.
Your exposure summary
Read this down the phone or paste it into a message to your vet. It stays on your device; nothing here is sent to DogSafe.
Why Hydrochlorothiazide (Microzide) needs caution
Hydrochlorothiazide makes the kidneys excrete salt and water, and it is used in dogs for particular conditions. Too much produces dehydration, low potassium and low sodium, with weakness, increased thirst and urination, and lethargy. The practical point specific to this drug is how often it appears as the second ingredient in a combination blood-pressure product whose name gives no hint of it, so a dog that swallowed "a blood pressure tablet" may have had two drugs, not one. Read the full ingredient list.
Part of the Furosemide (Lasix) guide
For related dog-safety questions and product-by-product answers, see the complete furosemide (lasix) guide.
Signs to watch for
Most commonly vomiting, diarrhea, drooling, or mild sedation; less commonly unsteadiness or weakness after a large amount
Related items
Check the exact item or ingredient before assuming two similar exposures carry the same risk.
What to do next
Count the remaining tablets against what the prescription should have left, note the strength and the time, and call your vet's line with that number.
🚨Step-by-step: what to do in the first 10 minutes →Available 24/7. A consultation fee may apply.
A closer look at hydrochlorothiazide (microzide)
Hydrochlorothiazide makes the kidneys excrete salt and water, and it is used in dogs for particular conditions. Too much produces dehydration, low potassium and low sodium, with weakness, increased thirst and urination, and lethargy. The practical point specific to this drug is how often it appears as the second ingredient in a combination blood-pressure product whose name gives no hint of it, so a dog that swallowed "a blood pressure tablet" may have had two drugs, not one. Read the full ingredient list. The details below use the specific facts for this exposure, rather than treating it like every other medication question.
1. Start with the exact exposure
For a closely related comparison, read Furosemide (Lasix). Your vet sets the dose, and it is specific to your dog's weight and condition. Nothing on this page is a dose to give. What matters after an accidental exposure is how much more than the prescribed amount was taken.
2. Use the facts to decide whether to monitor or call
Another helpful reference is Lisinopril (Zestril). For a single extra dose of your dog's own prescription with no signs, call your vet's line for advice before deciding anything. Do not double up a later dose to compensate, and do not stop a prescribed course on your own. Call if a whole container may have been emptied, if the amount is uncertain, if your dog is vomiting repeatedly or seems unsteady, or if this is a human product rather than your dog's prescription.
3. If the details are uncertain
Follow the first 10 minutes guide. Count the remaining tablets against what the prescription should have left, note the strength and the time, and call your vet's line with that number.
FAQ
Your vet sets the dose, and it is specific to your dog's weight and condition. Nothing on this page is a dose to give. What matters after an accidental exposure is how much more than the prescribed amount was taken.
For a single extra dose of your dog's own prescription with no signs, call your vet's line for advice before deciding anything. Do not double up a later dose to compensate, and do not stop a prescribed course on your own.
Call if a whole container may have been emptied, if the amount is uncertain, if your dog is vomiting repeatedly or seems unsteady, or if this is a human product rather than your dog's prescription.
- Merck Veterinary Manual — poisonings from human prescription drugs (cardiovascular agents)
- ASPCA Animal Poison Control Center — human medications
- Pet Poison Helpline — top 10 human medications poisonous to pets
- Merck Veterinary Manual: Poisonings from human prescription drugs
- ASPCA Animal Poison Control
- Pet Poison Helpline: Top 10 human medications poisonous to pets