Do Cats Have Periods? No, and Here Is What Happens Instead

Female cats do not have periods. They have heat cycles, which is a different piece of biology with a different ending: instead of shedding the uterine lining and bleeding, a cat's body reabsorbs it. That is the whole answer in one line, and it is why a cat in heat is loud, restless and affectionate rather than bleeding on your bedding.

The rest of this page exists because the short answer raises the useful questions. What is a cat's cycle, then, and how often does it come around? Is a little blood ever normal? What does it mean when an unspayed cat does bleed, or leaves a discharge, and how fast should you act? And do toms, older queens, or moody pre-heat cats have anything that deserves the word "period"? Every figure below comes from a veterinary manual, a vet-authored page, or a peer-reviewed paper, and where those sources disagree we say so rather than picking one.

The short answer, and the mechanism behind it

Humans menstruate. A cat's reproductive cycle is an estrous cycle, and the two words are not synonyms. In a menstrual cycle, the lining of the uterus thickens on a hormonal schedule whether or not an embryo ever arrives, and when no pregnancy follows, that lining is shed and leaves the body as blood. In an estrous cycle, the lining only transforms fully in response to an actual embryo. Without a pregnancy there is no built-up lining to shed, and the modest preparation that did happen is quietly reabsorbed.

A UK veterinary nurse's page puts it in one sentence: "Cats reabsorb the lining of the uterus instead of bleeding it out so you will not see any blood during these times." The peer-reviewed version is the same story in longer words. A 2021 review in Frontiers in Reproductive Health describes the "spontaneous decidualization" that menstruating species undergo as "a rare and pre-emptive process occurring only in menstruating species." Cats are not one of them.

There is a telling silence, too. Merck's professional veterinary manual describes the dog's cycle with its bloody discharge in one section, then describes the cat's cycle in the next, and the feline section does not mention bleeding, discharge or menstruation at all. VCA's consumer guide to feline heat cycles, updated in 2025, does not use those words either. When two references written by reproduction specialists describe the whole cycle without once reaching for the word "blood," that is the answer.

The five phases of a cat's cycle

What a cat has instead of a period is a repeating cycle with named phases. The durations below are Merck's, from its 2024 reproductive-management chapter, and they explain why a queen can seem to be "in heat" for weeks at a stretch.

Two details in that table matter for the rest of the page. First, cats are seasonal: Merck's manual says a queen "requires at least 12 hours of light in order to have estrous cycles," which is why indoor cats under artificial light tend to cycle more often, and more of the year, than cats living by the sun. Second, ovulation in cats is triggered by mating rather than by the calendar, which is why a queen who is not mated can keep cycling every couple of weeks. Our cat in heat guide covers the signs, the frequency and the age it all starts.

That "induced ovulator" label is now known to be a simplification. A 2024 study in the Journal of Feline Medicine and Surgery sampled 29 intact queens at an Italian teaching hospital and found that 9 of them (31%) had ovulated without mating. The authors concluded that cats "should not be considered strictly induced ovulators," and they flagged why it matters: a queen who ovulates enters the progesterone phase that sets up conditions like pyometra, covered below.

Which animals actually menstruate

The menstruating club is small, and cats and dogs are not in it. A 2018 review in the Journal of Molecular Endocrinology counts the members: 78 higher-order primates (humans and Old World monkeys), four species of bat, the elephant shrew, and one spiny mouse, the common spiny mouse, which was only confirmed as a menstruating rodent in the 2010s. The same group's 2021 paper describes the bats more loosely as "several species," so the exact bat count is either four or a few more, depending on the paper.

Everything else, from horses to whales to cats, runs an estrous cycle and reabsorbs rather than sheds. The reason it evolved that way is still debated; the leading model links menstruation to that pre-emptive thickening of the lining, which only a handful of lineages developed. For a cat owner the practical point is simpler: a cat's body has no monthly bleed to have, so blood is never "her period."

Do cats bleed when they are in heat?

This is the question behind about a third of the searches that land on this page, and the honest answer has two frames, so here are both.

The UK veterinary charities and vet-authored pages say no, or so close to no that you will not see it. PDSA: "Unlike dogs, it's very unusual to see a cat bleed when she is on heat." A vet-written page from Joii, published in October 2025: "The majority of cats don't bleed at all. Others bleed such a small amount that you may not even see as they groom and clean themselves often." Vet Help Direct, quoted above, goes further and says you will not see blood at all.

Two US veterinary clinic blogs use a softer frame: "some cats may experience a small amount of bloody discharge," minimal next to a human period, with one clinic listing "occasional light discharge, although heavy bleeding is rare" among the signs of heat. Both of those pages end on the same instruction as the UK ones: significant bleeding is not part of a normal cycle and belongs at the vet.

Why the two frames coexist is worth stating, because it is not a real contradiction. Cats groom constantly, and a spot small enough to be licked away in seconds is invisible to an owner, which is exactly what the Joii page says. So the working rule from every veterinary source read for this page is the same: no visible blood is the norm, a trace is possible, and anything you would call bleeding is a reason to call.

What bleeding or discharge can mean, and when to call

Blood or discharge from an unspayed cat is uncommon enough that the vet-authored sources treat it as a call-the-vet sign in itself, not something to watch for a few days. Here is the list of causes as a vet-authored page from the UK sets it out, grouped by how urgent the sources say each one is.

• Being in heat: the trace-or-nothing situation described above.
• A urinary problem, not a reproductive one: a bladder infection or inflammation can leave blood in the litter box that looks like it came from the wrong place. Cats.com's vet-reviewed page lists urinary tract infections among the causes of apparent vaginal discharge, and separately warns that fluid from the anal glands, brown and foul-smelling, is often mistaken for it. Our cat UTI and cystitis guides cover the urinary side.
• Vaginitis, a foreign body, an injury, a growth: inflammation, something lodged, trauma, or a polyp or tumor, each a vet visit.
• A miscarriage or a problem in labor: Merck lists "fresh blood or dark green discharge before any kittens are born" as a sign of dystocia, a difficult birth, and the same page names retained placentas as a route to metritis, a uterine infection after birth whose primary sign is "pus-like discharge from the vulva." A reddish-brown discharge for a few weeks after a normal birth, called lochia, is expected, should lessen over time and should not smell. Our cat giving birth guide carries the full labor thresholds.
• Pyometra: the one on this list that can kill, described in its own section below.

The thresholds, as two vet-authored pages word them, are worth keeping verbatim. Joii: call your vet as soon as possible for "visible discharge from your cat's vagina, straining to urinate, increased frequency of urination, lethargy, decreased appetite, vomiting." Cats.com: call immediately if the discharge is "thick, colored (either white, yellow, or green), bloody, foul-smelling, present in large volumes," or if the cat seems unwell in any other way.

Pyometra: the discharge that is an emergency

Pyometra is a bacterial infection of the uterus that follows the hormonal pattern of the cycle itself. VCA's explanation: after each heat, progesterone stays high for weeks and thickens the uterine lining in preparation for a pregnancy; over several cycles without one, the lining thickens until cysts form, the uterine muscle loses its ability to contract, and the white blood cells that would normally clear bacteria are held back. Infection follows. Merck's owner manual adds that it is less common in cats than in dogs, and that "signs can progress rapidly to shock and death."

It comes in two forms, and the difference decides whether you see anything at all. When the cervix is open, pus, often bloody, drains out, and it may show on the fur under the tail or on bedding. When it is closed, nothing drains, the abdomen may swell instead, and the cat gets sicker faster. VCA makes the point every owner should hear: "because cats are usually very concerned with cleanliness, the discharge is usually cleaned up before it can be seen." A queen who has recently been in heat and is suddenly lethargic, drinking more, vomiting or off her food is the picture, discharge or not.

The numbers, with their frames, because the sources do not agree on one. In Swedish insured cats (1999 to 2006), the incidence was about 17 cases per 10,000 cat-years, cats were diagnosed at a median age of 4 years, the rate rose markedly after age 7, and 5.7% of affected cats died.

A 2016 review in JFMS gives an average age of 7.6 years at presentation, a different measure on a different population, and adds that signs "most commonly occur within 4 weeks of the onset of oestrus." On timing, VCA says pyometra "usually occurs two to eight weeks after the last estrus," and Joii says symptoms "usually develop up to 4 weeks after your queen's last heat ends": read those as the same window described from two starting points, not as a disagreement to resolve.

Treatment is usually surgery; Merck notes that of cats treated medically instead, 70% may still be fertile, but recurrence is common. Our pyometra guide has the full picture.

Do male cats have anything like a period?

No. Merck's anatomy chapter describes the ovaries in terms of estrous cycles and the testes in terms of continuous function: testosterone "is required for development and function of accessory glands (such as the prostate), sexual organs, male sex characteristics, and sexual behavior," with no cycle and no season attached. What owners read as a tom "in heat" is a tom responding to a queen who is: the yowling, the restlessness, the spraying and the urge to get out are his reaction to her cycle, not one of his own. If the spraying is the problem, our cat spraying guide is the page.

Do cats go through menopause?

No, and this surprises people. Cats keep cycling, and can keep getting pregnant, for life. PDSA: queens "tend to have slightly fewer cycles as they get older," but "most continue to come into heat and remain fertile until they are speyed." Joii's vet-written FAQ adds a line worth keeping: a cat whose cycles have stopped altogether "should be examined by a vet, as this can signal an underlying health condition." Fewer heats with age is normal; no heats at all is a question for the clinic, not a retirement.

Is "cat PMS" a real thing?

Not as a veterinary condition. No veterinary manual, charity page or peer-reviewed paper read for this page describes a premenstrual-syndrome equivalent in cats, and it would be hard to have one without a menstrual cycle. What owners describe as PMS is almost always the run-up to heat and heat itself: the restlessness, the vocalizing, the sudden clinginess, the rolling and rubbing. Those are the normal signs of estrus, covered in the heat guide, and they stop with spaying. A cat who vomits or goes off her food on a schedule is not showing a mood; she is showing a symptom, and that is a vet conversation.

What the cycle means for spaying

The reason vets bring up the cycle at all is what it sets up. Every ovulation, mated or spontaneous, opens a progesterone phase, and the 2024 Padova study spelled out the consequence of the 31% spontaneous-ovulation figure: the risk of "progesterone-dependent conditions (cystic endometrial hyperplasia, pyometra complex, feline mammary hypertrophy) is increased in these queens." Spaying removes the ovaries and the cycle with them, which is why every source on this page treats it as the prevention rather than an option. Timing, cost in each of our four markets and what recovery looks like are on our cat neutering guide, and if she is already in heat when you book, that question has its own page.

What to take away

• Cats do not menstruate: a queen's uterine lining is reabsorbed rather than shed, so a heat cycle produces behavior (calling, rolling, restlessness), not bleeding.
• The feline cycle has five phases in Merck's manual, with estrus lasting 2 to 19 days and an 8-to-10-day gap before the next one when no ovulation occurred; cats need at least 12 hours of daylight to cycle.
• Menstruation is limited to 78 higher primates, four or so species of bat, the elephant shrew and the spiny mouse (Bellofiore 2018, 2021); cats and dogs are not on the list.
• On bleeding in heat, UK vet charities say it is "very unusual" and two US clinics say a small trace is possible; every veterinary source agrees that visible bleeding is not a normal part of the cycle and is a vet call.
• Blood or discharge from an unspayed cat can come from a urinary problem, an injury, a growth, a birth complication or pyometra, a uterine infection that ran at about 17 cases per 10,000 cat-years in Swedish insured cats and can turn fatal within days.
• Toms have no cycle, queens have no menopause and keep cycling for life, and "cat PMS" is the normal run-up to heat with a human label on it.