Heat in Female Dogs: Cycle, Duration and Tips

Somewhere between six months and the first birthday, the time comes for most female dogs: the first heat announces itself, and the puppy slowly becomes an adult female dog. For many owners this raises questions – how long does the whole thing last, what changes in her behaviour, and what do I need to watch out for during these weeks? The good news first: heat is no cause for worry, but a completely natural part of the female cycle. You just need to know what is going on.

This guide explains, one step at a time, when the first heat comes, how the cycle runs through its four phases, how to recognise heat and how to guide your female dog well through this time – including two health topics closely connected with it: false pregnancy and the dangerous womb infection. For anything that concerns your particular dog, however, your vet is always the best person to ask: every dog is different, and this text cannot replace a veterinary examination.

The First Heat: When It Begins

For most female dogs the first heat sets in between about six and twelve months – a wide range that has a lot to do with size and breed. As a rule of thumb: the smaller the female dog, the earlier she usually becomes sexually mature. Small breeds can come into heat for the first time at around six months, while large and very large breeds take more time – with them the first heat often comes only at around ten months or later, and in some giant breeds not until after 18 months of age. Which size class your dog will eventually reach, and hence roughly when to expect the first heat, you can look up in our breed wiki.

A fixed date on the calendar still cannot be derived from this, and that is entirely normal. If, however, the first heat fails to appear well beyond the second year of life, a visit to the vet makes sense. Important to know: at her very first heat a very young female dog is indeed physically fertile, but neither physically nor emotionally mature for offspring – a mating in this early phase should be prevented at all costs.

How Often and How Long? The Cycle at a Glance

Unlike many wild animals, the female dog does not follow the seasons – heat can occur at any time of year. On average, a female dog comes into heat about twice a year, that is roughly every six months. Here too size plays a role: smaller females are often in heat twice a year, while some large breeds go into their cycle only once a year; overall the interval usually lies between six and twelve months. In the first year or two the rhythm may still be somewhat irregular – over time, most females settle into a fairly reliable, personal rhythm.

The cycle itself is divided into four consecutive phases that flow smoothly into one another:

• Proestrus (pre-heat), on average around nine days (roughly 3 to 17 days): the vulva swells and a bloody discharge appears. The female already attracts male dogs, but is not yet ready to mate herself and rejects advances.
• Estrus (standing heat), likewise around nine days (roughly 3 to 21 days): the fertile phase. The discharge becomes lighter and more watery – from dark red to pale pink and clear. Now the female is ready to mate and shows the standing reflex: she stands still and moves her tail to the side. It is during this time that mating and pregnancy occur.
• Metestrus (post-heat) or diestrus, up to about two to three months: the hormonal phase after heat, in which the corpus luteum hormone progesterone dominates – regardless of whether the female was mated or not. During this time a false pregnancy can occur.
• Anestrus (resting phase), several weeks to months: the hormonal rest period with no outward signs. The female is not fertile now.

When people colloquially say a female dog is "in heat", they usually mean the visible bleeding phase of pre-heat and heat combined. It lasts around two to three weeks in total – and that is precisely when special attention is called for.

How to Recognise Heat

The signs are usually easy to spot once you know what to look for. The clearest physical sign is the swollen vulva together with the bloody discharge, which becomes lighter and more watery over time. Many females also urinate more frequently and mark more than usual. Added to this are often subtle changes in temperament – some females seem more restless, more playful or more clingy, others withdraw – and the increased interest of the male dogs in the neighbourhood is usually impossible to miss. Good to know: not every female bleeds visibly. Very clean females in particular lick themselves so thoroughly that the bleeding is easily overlooked – which makes it all the more important to watch the other signs and your own calendar.

Tips for the Time of Heat

The most important rule for a female dog in heat is: stay on the lead. However great the joy of romping freely usually is – during heat the female belongs consistently on the lead on walks, and that for the whole of the roughly three weeks. If another dog comes into view, she is put back on the lead at once. During this time, avoid dog meadows, off-lead areas and popular meeting spots, and move your walks to quiet times of day and little-used paths.

Just as important is safety at home: garden, fence and doors should be well secured. Do not underestimate how far unneutered male dogs can smell a female in heat – they are drawn in from astonishing distances, and a mating is over in seconds. So never rely on a "quick sniff off the lead". Indoors, heat pants can keep the home clean – but they are no protection against the attraction to males outdoors. Give your female calm affection and rather leisurely activity in these weeks; because of the hormones, many are a little more sensitive than usual.

Behind this lies a larger thought: preventing unwanted offspring is part of responsible dog ownership. Anyone who wants puppies should inform themselves thoroughly beforehand – for example in our article on buying a dog responsibly – and never leave the pairing to chance. If an unplanned mating does happen, our puppy checklist will help you with the next steps; your vet should be on board early in any case.

False Pregnancy and Womb Infection

In the weeks after heat – during metestrus – two things can occur that are closely linked to the hormone balance. The first is false pregnancy. Because the hormonal situation after heat resembles a real pregnancy, some females behave as if they were expecting offspring even though they were never mated: they build a "nest", mother soft toys or playthings, seem clingy or restless, and milk production can even set in. A mild false pregnancy is common and usually subsides on its own. Important: do not restrict water on your own initiative and never milk the teats – that only stimulates milk production further. If your female is heavily affected, produces a lot of milk or the whole thing drags on, have her looked at by the vet.

The second topic is more serious: the womb infection (pyometra), a severe, potentially life-threatening accumulation of pus in the uterus that typically develops in the weeks after a heat – especially in older, unspayed females. You should know the warning signs: marked tiredness and lethargy, loss of appetite, conspicuously increased drinking and urinating, vomiting, fever, a distended belly and sometimes a purulent or bloody discharge. What makes it tricky is that a "closed" pyometra can run its course with no discharge at all – then the most obvious sign is missing, and the disease is all the more dangerous.

A pyometra is an emergency. If your female shows such symptoms in the weeks after heat, do not wait but drive to the practice immediately – and if it is evening, night or the weekend, our overview of emergency vets will help you. The sooner you act, the better the chances.

Spaying: Ending Heat for Good

Anyone who wants to end the cycle permanently sooner or later considers spaying. It ends the heats for good and at the same time removes the risk of a womb infection as well as of unwanted offspring. At the same time, the procedure is an operation with pros and cons that need to be weighed carefully – from the right timing, through possible effects on metabolism and coat, to the individual circumstances of your dog. There is no blanket recommendation; whether and when spaying makes sense is best decided calmly together with your vet. We have gathered all the arguments and methods in our detailed article on spaying the female dog.

When to See the Vet

The vast majority of heats pass completely without complications and need no veterinary support. In a few situations, though, it is better to call once too often than too seldom: with a first heat that fails to appear well into the second year of life; with a very irregular or conspicuously changed cycle; with a false pregnancy that heavily affects your dog or does not subside; and with any suspicion of an unwanted mating. And once more in all clarity: if your female shows lethargy, loss of appetite, heavy drinking or vomiting in the weeks after heat, that is an emergency – then every hour counts. For all other questions, you will find competent contacts in our directory of vets.

The bottom line is that heat is nothing to be afraid of. With a little knowledge about the cycle, a consistent lead in the crucial weeks and an alert eye for the few serious warning signs, you will guide your female calmly and safely through this time. This guide gives you general orientation for that – but the individual assessment always remains a matter for your vet.