Spaying your female cat or neutering your male: when, how much it costs and what changes
For cats, neutering is not a lifestyle choice: it is the most important health and household decision of the first year. Here is when to do it, what it costs, what the risks are and why most of the myths that go around do not hold up.
Why with cats it is almost always the answer
With dogs there are reasonable debates about age and size. With cats, feline vets agree far more: an entire male or female cat living in a home has a hard time and makes life hard for everyone else. An entire queen comes into heat again and again for months, yowls at night, tries to escape and, if she gets out, comes back pregnant. An entire tom sprays very pungent urine on walls, curtains and the sofa, fights if he has outdoor access and runs off as soon as he smells a female several streets away. Then there is health: early spaying greatly reduces the risk of mammary tumours in the female, which in this species are malignant in the vast majority of cases, and it eliminates pyometra (infection of the womb) and ovarian problems. In males, testicular tumours disappear and fighting drops sharply, and with it bite abscesses and the spread of feline immunodeficiency virus (FIV).
What the law says in Spain
In Spain, Law 7/2023 on the protection of the rights and welfare of animals requires cats to be surgically neutered before six months of age, except those listed on the breeders' register. It is a general obligation for males and females, whether the cat lives in a flat or goes outside. In practice, how it is enforced and what fines apply depends on the implementing regulations and on each region and town council, and many local bylaws already required something similar for cats with outdoor access. Beyond the fines, the law responds to a real problem: unwanted litters are the main source of abandoned cats and of growing colonies. If you have questions about your own situation, Michipedia's regulations page sums up what each Spanish region requires.
At what age: earlier than you were told
The old advice to wait until after the first heat is outdated. Current feline guidelines (International Cat Care, the ISFM and the AAFP) recommend neutering at around four or five months, before sexual maturity, and many rescue groups do it even earlier, from eight or ten weeks and above a minimum weight, with very good recovery. There is no proven benefit in letting a female have a season or a litter first; on the contrary, every heat that passes reduces the protection against mammary tumours. A female cat can get pregnant at four months, especially in spring, so waiting "until she grows a bit" is exactly how many surprise litters happen. Adults can be neutered at any age after a pre-surgical check.
What the operation involves
In males, castration (orchiectomy) is a short procedure: the testicles are removed through two small incisions in the scrotum, usually with no external stitches, and the cat goes home the same day. In females it is abdominal surgery: the ovaries are removed (ovariectomy) or the ovaries and womb (ovariohysterectomy), through the flank or the midline of the belly, and there are usually internal or external stitches. Both are done under general anaesthetic, and the anaesthetic risk in a young, healthy cat is very low. Beforehand the vet will examine the cat and, depending on age, may suggest pre-anaesthetic blood tests. You will be asked to withhold food for a few hours the night before, but in small kittens this fast is short: follow exactly what you are told.
How much it costs in Spain in 2026
Typical ranges at private clinics in Spain are 60 to 150 € to castrate a male and 130 to 300 € to spay a female, with notable differences between cities and depending on whether the price includes pre-surgical bloods, pain relief, a cone (Elizabethan collar) or post-op body suit and the follow-up check. If the female is in heat, pregnant or overweight, the price may go up. Many town councils and rescue groups run reduced-price neutering campaigns, especially for colony cats through TNR (trap, neuter, return) programmes, and quite a few clinics offer fixed prices for kittens. If you adopt from a rescue, the cat will normally already be neutered or have the appointment included in the adoption fee.
Recovery at home
For the first few hours the cat will be drowsy and a bit clumsy: keep them in a quiet, warm room with water, the litter tray nearby and nowhere high to climb up and fall from. Food is reintroduced in small amounts that same evening or as instructed. For about ten days you need to stop them licking the wound, with a cone or, in females, a surgical body suit, which many cats tolerate better. Check the incision every day: a little redness is normal; increasing swelling, discharge, the wound opening, or a cat that is flat and not eating is not. For males, for a few days it is better to use shredded paper or a non-sticking litter instead of fine clumping litter. And pain is controlled with the veterinary pain relief you are given: never with human medicines.
What changes and what does not
Heats disappear, as does the night-time calling and, in the vast majority of males, urine spraying; if he had been doing it for a long time, it may take a few weeks to fade and in some cases it stays as a habit. Fighting and roaming drop sharply. What does not change is personality: a playful cat stays playful and does not become "sad" or "lazy" because of the operation. A female does not need to give birth once to be balanced, and a male does not miss anything: these are human ideas projected onto an animal that experiences heat as stress. What does change, and it is worth knowing from day one, is metabolism.
The only common side effect: weight gain
After neutering, energy expenditure falls and appetite rises, a combination that within a few months turns many cats into overweight cats. It is not inevitable. Typically they need around 20 to 30 % fewer calories than before, so weigh the portion on kitchen scales rather than by eye, switch to a food for neutered cats or simply adjust the amount of the current one, split it into several meals and keep up daily play. Weigh the cat every month during the first year. A cat that gains weight after the operation does not do so because of the operation itself, but because they are still being fed like an entire, growing cat.
Real risks and myths
Every anaesthetic carries a risk, but in young, healthy cats it is low and far smaller than that of the complications it prevents. For years there was debate about whether early castration narrows the urethra in males and makes urinary blockages more likely: studies have not confirmed it, and the risk of blockage has more to do with weight, inactivity, low water intake and stress. Nor is there evidence that early neutering affects growth in any meaningful way. What is proven is that the most common alternative, the contraceptive pill or injection to stop heats, is linked to mammary tumours, pyometra and diabetes, and is not a long-term option.
If she is older or in heat
It is never too late to neuter, although the protection against mammary cancer is smaller if the female has already had several heats. A cat in heat can be operated on, although the womb has a richer blood supply and some vets prefer to wait until it ends; if she is pregnant, the decision should be discussed calmly with the vet. In adult and older cats, blood tests are usually done first to tailor the anaesthetic. And if you have adopted a cat from the street without knowing whether they are neutered, the vet can check: in females there is sometimes a small scar on the flank, or an ear tip if the cat went through a TNR programme.
Neutering at four or five months prevents litters, heats, spraying, fights, mammary tumours and pyometra, and in Spain it is also what the law requires. The only usual side effect is weight gain, and you can control it by weighing the food from day one.
Educational content from Michipedia, translated from the Spanish original. It does not replace the advice of a vet or a feline behaviour specialist. Every cat is an individual.