Dr. Mark is a veterinarian with over 40 years of experience in the field. He works with dogs, cats, exotics, and livestock.
You should worry about your cat getting pregnant. Even if your cat only breeds occasionally, a single cat is able to produce hundreds of kittens in her lifetime. Her kittens are able to produce too, and so on, and so on. A single cat can have thousands of descendants in only a few short years.
Should You Spay Your Cat?
Most of you are already aware that you can have your cat spayed at your local veterinary clinic. The surgery is not expensive, there are few negatives and lots of positives, and the most common procedure we perform is an ovariohysterectomy, which removes the uterus as well as the ovaries so your cat no longer runs the risk of health problems during pregnancy, no longer howls during heat nor runs off in order to be bred.
It is permanent though.
Not everyone wants a permanent solution, not everyone in the world has a local veterinary clinic, and not everyone has the money to take their cat in for surgery. There are other alternatives for those cat families that cannot have or do not want this permanent solution.
Why Put My Cat on Birth Control?
The truth is that most people do not want to bring home one of your kittens. If you have a very special and rare breed cat, have a large number of people that have already asked for kittens, and are willing to find homes or take in the kittens that the new owner does not want or brings back, then you may be justified in breeding your cat.
Otherwise, leave it to the breeders who deal with this issue all of the time.
Are you going to leave it to the breeders but still need birth control? An important reason for putting a cat on birth control instead of having her spayed is that there is just no means to do so in some areas. In order for a cat to have an ovariohysterectomy, she must go under general anesthesia and have her abdomen surgically invaded. This is a pretty routine thing in most clinics in many parts of the world but is a problem in some areas. In other parts of the world, birth control hormones might be available and cheap but surgery is not an option.
Reasons to Use Birth Control
- Interested in breeding cat later
- No veterinarian available
- Hormones are available and easy to use when surgery is not a possibility.
Best Methods of Temporary Birth Control in Cats
Hormone Pills or Drops
This option is not nearly as popular as hormone injections, but megestrol acetate pills might end up a good choice for those that cannot spay their cats. It can be made up as either pills or drops and is given in food; cats get about 2.5 mg once a week but if they are already in heat the first time need a larger dose for three days. If cats are fed together, one cat can get the dose meant for another and both cats can have problems.
Megestrol acetate used to be a birth control for dogs too but is not used anymore since it provoked breast cancer. One popular website for an organization that deals with feral cats says that it is safe and effective, but there is no proof that is effective for feral colonies, and there are some serious health issues (cancer in unborn kittens, diabetes, and mammary disease in adults). It is not FDA-approved.
It has not been used enough in cats for all of the side effects to be seen and written about, and since it is not approved and there are other solutions for feral cats (like trap/neuter/release programs) it will probably not be popular enough to warrant studies. Although it is an option for those people that feed feral cat colonies and cannot catch their cats, I still think hormone injections are a better alternative for those that cannot spay and neuter.
- easy to administer in food
- must be formulated at a compounding pharmacy since it is not available to purchase
- side effects
The most common type of birth control injection that we use in cats is a progestin type compound called medroxyprogesterone acetate. It is a prescription drug in the US and is sold under the brand name Depo Provera. It is available over the counter in some countries and may be available at some feed stores.
Side effects like hair loss, increased water consumption, and diabetes have all been reported. If the injection is given at the wrong time it can cause a cat to develop an infection in her uterus.
Cats only need the injection about every 4 months, either 3 weeks or more after being in heat or 3 weeks after having kittens. The dose is 2-4 mg/kg and in some countries, small vials are available for sale at pet and feed stores.
- relatively easy to find and use
- effective for 4 months
- difficult to administer for some
- potentially serious side effects, especially if given at the wrong time
One of the problems with giving an injection is that the cat has to be taken to the vet every three or four months. With the hormone chip, this is not an issue since it lasts so long. A 4.7 mg GnRH (deslorelin) chip is placed under the skin and research has shown that it is effective for about 24 months.
Once the chip has worn out the cats are fertile again and have been bred successfully.
No serious health problems have yet been discovered. In some cats, though, the chips can actually stimulate them to go into heat right after the implantation. In others, the heat can happen as soon as 15 months after the implant is in place, and in no case can the owners be sure when the cat is going to start coming into heat again.
Hormone chips are a good option where available since they do not have the side effects of pills or injections and are reversible.
- few if any side effects
- fewer visits to the vet since the chip lasts longer than the injection
- can have a fertile heat right after the chip is placed
- not sure how long the chip will last and heat cycles will return
- relatively expensive to administer
This is a great alternative but unfortunately, demand is low and it is only available in some places. Melatonin pills cannot be used since they have such a short half-life so an 18 mg melatonin chip has to be placed under the cat´s skin to be effective in birth control.
There are few reported side effects, mostly problems when mixing with other medications. It only lasts about 2 to 4 months and cats have to be watched closely to see when they are going into heat again, at which time the family can take them in for another chip.
- few or no side effects
- not available everywhere
- chips only last about as long as the injection so more vet visits are necessary than with the hormone chip
Natural Birth Control
Avoiding males is obviously the most natural method of birth control but any cat owner knows that this is not so easy. Cats can run away as soon as the door is opened so if you want to try something a little stronger; one natural product that has been recommended is wild carrot seed oil.
Women have used this natural product for a long time before any of the hormonal birth control methods were available. There are fewer side effects. There are companies that will sell the product but it is neither labeled for cats nor are there any published dosages.
Several sources claim that the wild carrot seed oil is 98% effective, almost as good as hormone injections. That project was in humans, though, and this is based on anecdotal evidence, not backed up by any controlled studies; like all anecdotal information, it needs to be accepted cautiously. If you do not want or cannot spay your cat, and do not want to give hormones because of the potential side effects, this may be an effective alternative.
- no reported side effects
- no research on cats
- no available doses to use with cats
- may not be effective
What if Something Goes Wrong?
If you have to put your cat on temporary birth control but she becomes pregnant, there are a few alternatives. The best, in my opinion, is to go for the permanent solution. Take your cat to your local vet and have her surgically altered so that she no longer has kittens. Of course, that is not always the best option.
The second option is to let her have the kittens.
Potential Health Problems After Bearing Kittens
- Bleeding from the uterus
- Prolapsed uterus (the womb is pushed out of the body)
- Behavioral changes (usually no longer playful with the family, but some cats kill their kittens)
- Uterine infection and secondary vomitingMastitis (infection of the mammary glands)
- Death (usually from bleeding)
Since this was an accidental breeding, the kittens may not even have a home. Do you really want to take them to a shelter and have them put down? Most animals in the shelter are never adopted.
The last option after an accidental breeding is to give a "morning-after pill" to terminate the pregnancy. There is not actually a pill available for cats at the pharmacy, but there are several drugs that can be used.
These hormones can stop a pregnancy from developing. There is no data about whether these drugs work or what doses to use with cats and even with dogs they have to be given just after mating is confirmed with a vaginal swab. There can be serious side effects so I would not recommend using diethylstilbestrol or any of the other estrogen hormones in a cat.
The drug available for use in cats, prostaglandin (Lutalyse) causes the cat to stop producing progesterone so she loses the kittens. There are side effects. The cat needs to be about half way along before it will work but even a low dose that does not have many side effects will probably work. (Even low doses can cause a cat to start vomiting though.)
Usually given to cats as an anti-inflammatory, this steroid will cause cats to lose their kittens if given orally over several days. Although it normally works and has only mild side effects there are problems if cats have other health problems, and an ultrasound should be done to make sure that the kittens are no longer present.
Combination Drug Therapy
Most cat owners still opt for one of the solutions already listed but there are some new drugs that may be more effective and have fewer side effects. Cabergoline, cloprostenol, and aglepristone are great drugs for this problem but are expensive and not always available like the others listed.
Kutzler MA. Alternative methods for feline fertility control: Use of melatonin to suppress reproduction. J Feline Med Surg. 2015 Sep;17(9):753-7 https://pubmed.ncbi.nlm.nih.gov/26323798/
Furthner E, Roos J, Niewiadomska Z, Maenhoudt C, Fontbonne A. Contraceptive implants used by cat breeders in France: a study of 140 purebred cats. J Feline Med Surg. 2020 Oct;22(10):984-992. https://pubmed.ncbi.nlm.nih.gov/32081074/
Fontaine C. (2015). Long-term contraception in a small implant: A review of Suprelorin (deslorelin) studies in cats. Journal of feline medicine and surgery, 17(9), 766–771. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5117121/
Schäfer-Somi S. Effect of melatonin on the reproductive cycle in female cats: a review of clinical experiences and previous studies. J Feline Med Surg. 2017 Jan;19(1):5-12. https://pubmed.ncbi.nlm.nih.gov/26467539/
Romatowski J. Use of megestrol acetate in cats. J Am Vet Med Assoc. 1989 Mar 1;194(5):700-2. https://pubmed.ncbi.nlm.nih.gov/2647696/
Eilts BE. Pregnancy termination in the bitch and queen. Clin Tech Small Anim Pract. 2002 Aug;17(3):116-23. https://pubmed.ncbi.nlm.nih.gov/12476814/
Tan, S., Stellato, A. C., & Niel, L. (2020). Uncontrolled Outdoor Access for Cats: An Assessment of Risks and Benefits. Animals : an open access journal from MDPI, 10(2), 258. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7070728/
Kitts-Morgan SE. COMPANION ANIMALS SYMPOSIUM: Sustainable Ecosystems: Domestic cats and their effect on wildlife populations. J Anim Sci. 2015 Mar;93(3):848-59. https://pubmed.ncbi.nlm.nih.gov/26020863/
This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.