Mirtazapine Dosage Calculator for Dogs
Enter your dog’s weight to see the standard mirtazapine dosing guidance.If your veterinarian just prescribed mirtazapine dosage for your dog, you’re probably asking yourself right now, how much should I give him? This is what this guide will address first, and then we will delve into all you need to know about it, how it works, what to look for, etc.
Medically informed guide. Not a substitute for veterinary advice – always confirm dosing with your vet before giving any medication.
Key Takeaways
- For dogs, the typical dose of mirtazapine is 0.6–1.3 mg/kg orally every 24 hours, not to exceed 30 mg daily.
- Mirtazapine Dosage For Dogs is not available in dog-specific strengths so most vets will prescribe a specific strength (human tablet size) for each dog based on weight bands (7.5, 15, 30, 45 mg).
- Mirtazapine is used “off-label” (extra-label) in dogs, meaning it is FDA approved for use in cats for weight loss (as Mirataz) but has not been approved for any use in dogs.
- Common side effects include sleepiness, sedative effects, and lack of coordination.
- Never give mirtazapine if your dog is allergic to it, or is currently on linezolid, selegiline (Anipryl), or amitraz (Mitaban, or amitraz flea/tick dips) — these combinations can cause serotonin syndrome.
- A 2025 clinical study found dogs given mirtazapine were about 3 times more likely to start eating again than untreated dogs, with most dogs eating within about 2 hours of the dose.
What is Mirtazapine For Dogs
Mirtazapine dog dosage is a tetracyclic antidepressant drug (Remeron) used off-label by veterinarians in dogs to stimulate appetite and prevent nausea.
It work on multiple pathways in the body, blocking chemical messengers in the brain that can cause nausea, vomiting and loss of appetite.
It is usually prescribed by vets for dogs who are not eating because of:
- Chronic kidney disease
- Side effects of other treatments, such as cancer.
- Liver disease
- In general, if the person is ill or if they feel sick.
Mirtazapine transdermal ointment is an FDA-approved drug for cats to prevent unwanted weight loss under the brand name Mirataz, but currently isn’t FDA approved for use in dogs as a veterinary medicine (as an ointment, tablet or other form). Therefore, it is always used off label in dogs, in the form of human strength pills (7.5/15/30/45 mg) or a compounded liquid/capsule.
Mirtazapine Dosage Chart For Dogs By Weight
This is the absolute Mirtazapine dose rate for dogs that most vets use and is in the ratio of human tablet size. It is the same weight-band system found throughout the veterinary pharmacy literature.
| Dog’s Weight | Typical Dose | Frequency |
| 6–11 lbs (2.7–5 kg) | 3.75 mg | Once every 24 hours |
| 12–29 lbs (5.4–13.2 kg) | 7.5 mg | Once every 24 hours |
| 30–54 lbs (13.6–24.5 kg) | 15 mg | Once every 24 hours |
| 55–75 lbs (25–34 kg) | 22 mg | Once every 24 hours |
| Over 75 lbs (34+ kg) | 15 mg twice daily, or 30 mg once daily | Every 12 hours, or once every 24 hours |
How to use this chart: Your dog’s weight will be listed in the left column and that’s the typical starting dose your veterinarian will suggest. This chart is based on a standard mg/kg dose range (0.6-1.3 mg/kg/day), rounded to doses that can actually be achieved by using the commercially available 7.5, 15, 30, and 45 mg tablets, as there is no mirtazapine tablet specifically made for dogs.
A separate weight-based protocol used in a 2025 clinical trial on dogs rounded slightly differently by kilogram: under 7 kg received 3.75 mg, 8–15 kg received 7.5 mg, 16–30 kg received 15 mg, and dogs over 30 kg received up to 30 mg, all once every 24 hours. The two charts land in the same range — small differences exist because vets round to the nearest practical tablet fraction.
No chart is ever as important as your vet’s specific instructions, and your vet will consider your dog’s health history, liver and kidney function and the precise strength of tablet available.
What Is Mirtazapine Used For in Dogs?
Mirtazapine for dogs dosage is a tetracyclic antidepressant drug, which was originally developed for humans (under the brand name Remeron), that is used in dogs primarily as an appetite stimulant and anti-nausea medication.
It does this by inhibiting certain serotonin and histamine receptors that are associated with nausea, and increasing the release of two chemicals called norepinephrine and serotonin, which will make a dog who is feeling sick feel less nauseated and hungrier, although the illness may not have gone away.
It is a common ingredient in veterinary medicine for dogs that are not eating due to:
- It’s commonly prescribed for chronic kidney disease, one of the most common conditions.
- Nausea due to cancer and chemotherapy.
- Liver disease
- Chronic nausea or vomiting from gastrointestinal disease
- General hospital inappetence (if an owner does not wish to try a feeding tube)
It is not used as frequently for a secondary purpose: as an add-on treatment for anxiety, fear or aggression related behavior problems, typically in conjunction with other drugs such as fluoxetine — but this is not its primary use in dogs.
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Is mirtazapine FDA-approved for dogs?
No. There is one FDA approved mirtazapine product, Mirataz, a transdermal ointment for cats to lose weight. Mirtazapine is always used off-label (also called extra-label), that is, a human or compounded drug is prescribed for use in dogs, and in this case the dosing instructions are based on clinical experience and a limited number of studies, rather than an FDA-approved label — a common and legal practice in veterinary medicine.
Does Mirtazapine Actually Work in Dogs? What the Research Shows
Until recently, experience with the use of mirtazapine in dogs was limited to that in cats, as formal dog studies were lacking. Until a 2025 study in the journal Animals found that, in reality, clinical results in two sections were:
- 107 dogs were retrospectively evaluated: Dogs receiving mirtazapine were approximately 3 times as likely to self-resume eating as dogs not receiving mirtazapine (68.6% vs. 37.5% of dogs improved).
- Placebo-controlled trial: 25 dogs treated with mirtazapine; 100% of dogs eating food on first day of treatment compared to 63.6% of dogs treated with placebo eating food on first day of treatment. Dogs that ate started eating 120 min on average after the dose. None of the treated groups reported any adverse effects.
What this translates to for you: Mirtazapine for dogs medication is really a doggy appetite stimulant that works within a couple of hours, not days, in an ill dog. However, the same study showed this was not as much of an effect on day two, therefore in some cases, it may be necessary to have a veterinary reassessment, as opposed to “set it and forget it”.
Mirtazapine Dosage for Dogs: The Full Details
Standard dosage
The most common dose range mentioned in veterinary pharmacy references is:
0.6–1.3 mg/kg by mouth, once every 24 hours, not to exceed 30 mg per day.
Some sources specify a lower range, 0.6–1 mg/kg, especially for dogs with compromised liver or kidney function, as the drug is not as effectively eliminated.
Why doses are usually “fixed,” not calculated to the decimal
Most dogs can’t be safely dosed to a precise mg/kg dose with mirtazapine tablets since they are only available in 7.5 mg, 15 mg, 30 mg and 45 mg. That’s why the weight-band chart above is there – it is rounded to the nearest usable tablet fraction for each weight range.
Your veterinarian may prescribe a compounded version of the drug (a flavored chewable tablet, smaller custom tablet or liquid) if your dog’s dose cannot be evenly divided using a commercial tablet of the medication. This is particularly prevalent with small sized dog breeds.
How often is it given?
Rarely more than once a day. The exception is dogs 75 lbs or more, which may be divided into 15 mg twice daily, or 30 mg once a day; either way, the total amount for the dog is 30 mg per day, and your veterinarian will determine which of these two works best for your dog.
How long does a dog stay on mirtazapine?
There is no set time limit. Some dogs may use it for a few days when they’re sick; others may use it for months under a vet’s care, especially for chronic kidney disease. As an antidepressant, it should not be discontinued suddenly after long-term use; consult your vet about resolving this issue.
How to give the dose
- Can be given with or without food. If your dog vomits after a dose when he or she has an empty stomach, consider feeding a small amount of food to accompany future doses.
- Don’t crush tablets. If your dog is a pill resister, place the tablet to the back of the tongue or have a demo with a pill-popper from your vet.
- When a dose is missed, administer as soon as possible unless the next dose is nearly due — then skip and continue with the normal schedule. Do not double dose to make up for missed doses.
Is Mirtazapine Safe for Dogs?
Yes, in general — mirtazapine is thought to be well tolerated in dogs, and the clinical trial in 2025 did not demonstrate any adverse effects in dogs with underlying kidney, liver or cancer diagnosis. However, this does not imply risk-free and a few groups require additional caution when it comes to “well-tolerated.
Do not use mirtazapine if your dog:
- Before, has had a reaction to mirtazapine
- Has used a monoamine oxidase inhibitor (MAOI) in the last 14 days (such as the antibiotic linezolid, the senior dog medication selegiline/Anipryl and the flea/tick treatment amitraz/Mitaban or some over-the-counter dips)
Use with caution, and expect closer monitoring, if your dog has:
- Liver, kidne or heart disease (usually results in a lower starting dose).
- A history of leukemia, diabetes, glaucoma, difficulty urinating, low platelets, or other blood disorders
- A pregnancy, or is currently nursing puppies
Make sure your vet is aware of all the medications, supplements and even flea/tick products your dog is taking, as some common combinations can put your dog at risk for serious side effects (see interactions table below).
Mirtazapine Side Effects in Dogs
At present, knowledge about the safety of the drug in larger dogs is scanty and relies on extrapolation from the cat where the drug is much more extensively studied. Side effects reported or possible are:
Most common:
- Drowsiness or sedation
- Poor coordination/wobbliness (ataxia)
- Low energy
Less common:
- Agitation, restlessness or talking.
- Salivation/salivating.
- Tremors or shakes in the muscles
- Low blood pressure
- Fast heart rate
- Increased liver enzymes (only detected in blood tests)
- Unusual changes in the bone marrow.
Side effects are usually dose-dependent, that is, the more that is given, the more frequently and severely they occur. Based on published accounts, it appears that dogs tolerate mirtazapine better than do cats.
Signs of serotonin syndrome – call your vet immediately
This is the severe side effect to be aware of, particularly if mirtazapine is prescribed in conjunction with another drug that increases serotonin. If you notice any of these symptoms, contact your veterinarian or emergency animal hospital immediately:
- Vomiting or diarrhea
- Agitation, restlessness or disorientation
- Fever
- Shaking, twitching or stiffness of muscles
- Dilated pupils
- Excessive vocalization
- Loss of coordination
- Seizures
Mirtazapine Drug Interactions in Dogs
| Interacting Drug | Why It Matters |
| Linezolid (antibiotic) | MAOI — risk of serotonin syndrome; requires 14-day gap |
| Selegiline (Anipryl) | MAOI — risk of serotonin syndrome; requires 14-day gap |
| Amitraz (Mitaban, some flea/tick dips) | MAOI — same 14-day washout rule applies |
| Tramadol | Increases serotonergic effect, raising serotonin syndrome risk |
| SSRIs (e.g., fluoxetine, fluvoxamine) | Additive serotonergic effect |
| Tricyclic antidepressants (e.g., clomipramine) | Additive serotonergic and sedative effect |
| Benzodiazepines (e.g., diazepam) | Can intensify sedation |
| Clonidine | Combined sedative/blood pressure effects |
| Cimetidine | Can slow mirtazapine metabolism, raising drug levels |
Be sure to let your veterinarian know of all medications, supplements and topical flea/tick products your dog is using, especially if it is a flea/tick dip that you buy over the counter containing a topical medication called amitraz.
Can Dogs Overdose on Mirtazapine?
Unfortunately, Mirtazapine dosage overdose has not been studied specifically in dogs, but based on the studies of human overdose, excessive doses are likely to worsen the same effects: intense sedation, disorientation, rapid heart rate and in severe cases, more serious effects. The maximum daily dose for a dog should be 30 mg total per day.
In case of suspected overdose (such as a “double dose,” a dog obtaining the pill bottle, or any accidental overdose), reach out to your veterinarian, an emergency animal hospital, or an animal poison control center ASAP:
- ASPCA Animal Poison Control: 888-426-4435
- Pet Poison Helpline: 855-764-7661
Usually, these hotlines charge consultation fees, however this could be worthwhile if it is a potential emergency.
Mirtazapine vs. Other Dog Appetite Stimulants
If your dog is not a good candidate for mirtazapine use or your veterinarian chooses to use an alternative medication, here’s some information on how it compares to the primary alternatives.
| Medication | FDA-Approved for Dogs? | Typical Use | Notes |
| Mirtazapine | No (off-label) | Appetite stimulant + antiemetic | Once-daily tablet; also helps with nausea |
| Capromorelin (Entyce) | Yes | Appetite stimulant | Liquid formulation; the only FDA-approved option for dogs |
| Cyproheptadine | No (off-label) | Antihistamine, secondary appetite stimulant | Often tried if mirtazapine doesn’t work |
| Prednisone / steroids | Varies by product | Appetite stimulant (secondary effect) | Effective but carries more significant long-term side effects |
If you are looking for something that has been studied and is approved specifically for use in dogs, Capromorelin might be worth a chat with your veterinarian about, but when a dog’s loss of appetite is due to nausea from kidney disease, cancer, or gastrointestinal illness, mirtazapine may be the first treatment recommended.
How to Store Mirtazapine
- Keep at ambient temperature (about 68-77 F or 20-25 C).
- Keep medicine out of light and water
- Store compounded preparations as directed by the compounding pharmacy — directions may vary from standard tablets
- Ensure it is out of the reach of children and other family pets
Myth vs. Fact
Myth: “There is a dog specific form of mirtazapine available, so I can just get it.
Fact: There isn’t. All dog doses are made from human tablets or a compounding pharmacy – no FDA approved dog product.
Myth: “If a little works, more will work faster.
Fact: More does not necessarily mean better, or faster, and increases the risk of side effects. In the 2025 clinical trial, the latency to first eating was on average approximately 2 hours at standard doses, and doses do not accelerate this and rather increase risk.
Myth: “It’s basically the same as my dog taking some Benadryl or some over-the-counter appetite stimulator.
Fact: Mirtazapine dosage for dogs is not a supplement, it is a prescription drug that has real drug interactions (with some flea/tick products) and needs veterinary supervision.
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FAQs
What is mirtazapine used for in dogs?
Its main applications are as an appetite stimulant and an anti-nausea drug for dogs who are not eating because of illness; most commonly chronic kidney disease, cancer, liver disease, or general GI upset.
What dosage of mirtazapine can I use for my dog?
The typical dosage is 0.6 to 1.3 mg/kg PO q24h (maximum 30 mg/day) depending on your dog’s health condition, weight and individual veterinary recommendation. Refer to the weight chart above as a guideline, always use your veterinarian’s recommendations.
When does mirtazapine start to work for a dog?
Can start to work in as little as 12-24 hours and the clinical trial data shows that many dogs begin to eat within a couple hours of a dose. It takes one or two days before the full effects will be consistent.
Can Mirtazapine be used in dogs?
Yes, generally speaking, as it is already deemed to be quite tolerable and one 2025 clinical trial stated that there were no adverse effects. The side effect most frequently experienced is slight drowsiness. Should not be used in dogs with a history of drug allergy or when used in combination with MAOIs such as selegiline or amitraz.
Is it safe to administer mirtazapine dose on a daily basis to my dog?
Yes, as long as you’re following your veterinarian’s instructions. No definitive limit to the length of treatment is set, but it should be weaned off instead of discontinued.
What if my dog takes too much mirtazapine?
Call your vet or animal poison control center right away. The adverse effects of overdose have not been extensively studied in dogs, but research in humans suggests that dogs will experience increased sedation, disorientation, and rapid heart rate at the very least.
Does mirtazapine cause serotonin syndrome in dog?
Yes, especially when used in conjunction with other medications that affect serotonin, such as MAOIs, SSRIs, tramadol or tricyclic antidepressants. Be alert for agitation, shaking, dilated pupils, fever and loss of coordination, and seek immediate assistance if these symptoms are present.
Does Mirtazapine affect dogs’ sleep?
The side effects most commonly reported are drowsiness and sedation, particularly with higher doses.
May Mirtazapine be taken with food?
Yes but it can be administered either fed or fasted. If it is vomited on an empty stomach, you can try administering to your dog in the future with a small meal.
What is the difference between mirtazapine and Mirataz?
There is a transdermal (ointment) version of mirtazapine that is FDA approved, but only for cats, not dogs, and is called Mirataz. Instead, the oral tablet or a compounded version is given to the dogs.
What’s the difference between mirtazapine dosing in cats and dogs?
This is because the way the drug is metabolized in the cat is different – they have been known to need it much less often (every 48-72 hours), and dogs usually need it every 24 hours.
Is mirtazapine a good option for dog anxiety or is it better to use it for loss of appetite?
It is sometimes used off-label as an adjunctive to anxiogenic or phobic behavior, typically in combination with another drug, but this is not its primary or studied use in dogs.
Where to obtain mirtazapine for my dog?
It is a prescription-only product, and can be obtained from your veterinarian, which may ask you to visit a compounding pharmacy for a custom strength tablet, or dispense one of the standard human tablets.
If I forget to take a dose, what should I do?
Give it as soon as you remember, except when it is almost time for the next dose – then omit the dose. Do NOT administer a double dose.
Final Thoughts
But Mirtazapine Dosage For Dogs has emerged as one of the more effective off-label veterinary solutions that veterinarians turn to when a dog refuses food, and clinical research finally confirms what many veterinarians have seen anecdotally: it does work, it can work fast, and most dogs are able to tolerate it.
However, off-label” and “no dog specific formulation” indicate exactly the dosage is of major importance as opposed to a purpose built medicine. If you read the chart above, you will have an idea of what your veterinarian will likely prescribe, and why, but remember your veterinarian will make the final decision based on your dog’s weight, organ function, and other medications.
Don’t wait it out if your dog displays any of the unusual symptoms, particularly those of serotonin syndrome. Call your vet or the nearest emergency animal hospital right away.
