January 28, 2026, 4:47 pm | Read time: 5 minutes
A harmless sentence while out walking can quickly become a problem for owners of unneutered male dogs: “My bitch is in heat.” What follows is often pure stress—for humans and animals. But there is an alternative to surgery that more and more pet owners are taking advantage of.
If you’re the owner of an unneutered male dog and you hear the words “My female dog is in heat” from other dog owners during a walk, it might make you sweat bullets. Stress then becomes a foregone conclusion. Unlike cats, dogs are not usually spayed or neutered across the board. Furthermore, many owners are deterred by the cost of the procedure. A hormonal implant for dogs can serve as an alternative. Two experts explain what you need to bear in mind.
Temporary Solution for Behavioral Problems
When a female dog in heat is announced on a walk, many owners of an unneutered male dog become alarmed. The only thing that often helps to get the agitated animal under control is to put a lead on and quickly take a different route. But even that doesn’t always save you from stress. If you don’t want your pet to be permanently castrated, you can resort to a hormonal solution. “This implant continuously releases active substances and thus stops testosterone production,” explains Ursula von Einem from the German Association of Practicing Veterinarians.
The male dog becomes infertile as a result of the procedure and shows less sexual interest—an effect that can be seen in significantly smaller testicles, among other things. Depending on the preparation, the effect lasts for several months.
Castration Test – Without Surgery
This procedure is especially suitable for dogs for whom surgical castration is not an option, such as due to health reasons or for breeding males. However, many pet owners opt to use the implant as a way to first test the effects of castration.
“Some male dogs suffer a lot when female dogs are in heat. During this time, they become behaviorally conspicuous, lose a lot of weight, or constantly run away,” reports von Einem. In such cases, the hormonal measure can bring noticeable relief—but only if the behavior is actually caused by sex drive. It has no effect on problems caused by fear or a lack of training.
Different Variants – and How Long They Work
Axel Wehrend, a veterinary specialist in reproductive medicine at Justus Liebig University Giessen, explains: “There are two different implants on the market, which differ in terms of their active ingredient content and duration of action.” While the smaller model is effective for at least six months, the larger one usually lasts for a year, with individual fluctuations.
Once the effect wears off, the testicles enlarge again. A new treatment should then take place at the latest in order to avoid hormonal fluctuations.
Important: The follow-up chip must be inserted before the effect of the old one wears off completely.
Now Also Possible for Bitches
The method has been approved for male dogs in Germany since 2007. Recently, vets have also been allowed to use the smaller implant in bitches. While the hormones are active, the female dogs do not go into heat, thus they do not attract male dogs, and there is no bleeding, as Wehrend explains.
However, the therapy may only be started in very young bitches—and before puberty: “They must not yet have reached puberty,” emphasizes the expert. The first chip must therefore be placed at the age of twelve to sixteen weeks. After that, regular renewal is possible. However, for female dogs that are already sexually mature, the use of the chip is not recommended due to the risk of ovarian diseases such as cysts or infections, as well as continuous estrus.
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Only Permitted for Sexually Mature Males
Unlike with bitches, there is no maximum age for male dogs—but there is a lower age limit. According to Wehrend, it may only be used on animals that are already sexually mature. The reason: during development, the testicles migrate from the abdominal cavity into the scrotum, closing the inguinal clefts. If this process is not yet complete, reduced testicles may move back into the abdominal cavity.
Once the chip has been inserted, a so-called stimulation phase follows, during which the testosterone level temporarily increases. This manifests itself in increased sexual behavior. Only then does the desired effect occur. “How long the stimulation phase lasts varies from animal to animal, but it should be over after six weeks at the latest,” says Wehrend. “For many, the dampening effect sets in after around two weeks.” In rare cases, there is no effect at all—this is known as “treatment failure”.
Repetitions Possible Over the Course of a Dog’s Life
How often a dog may receive this hormone chip has not been conclusively clarified. Von Einem sees no problem with long-term use: The method is also feasible for life, he says. Wehrend is more cautious: “I myself know a whole series of male dogs that have already received their fourth implant,” he says, but points to the limited data available to date.
Among the few known side effects are changes in the coat, which may curl, become softer, or experience increased shedding. In addition, neutered dogs have a lower energy requirement. If they are not fed accordingly, this can result in obesity.
The German original of this article was published in March 2025.