Signs a Dog Is in Heat

Some owners are surprised by their dog’s first heat, and some miss the signs until a neighbour’s dog turns up at the gate. The signs are fairly consistent once you know what to look for, and they change in a recognisable way as the heat goes on. This guide lists the signs dog owners most often see, explains how they differ between the early and late part of the heat, shows what you can do to keep your dog comfortable and safe, and says when to pick up the phone. For the timeline and the stages, see how long a dog stays in heat.

The physical signs

A swollen vulva

The first and most reliable sign is swelling of the vulva, which becomes larger and firmer. It may be noticeable only to someone who looks, particularly in a long-coated dog. It often appears before any discharge.

Discharge

In the first stage, proestrus, which lasts about 9 days on average (2 days to 3 weeks in individual dogs), the discharge is usually bloody. In estrus, about 9 days on average, it often becomes thinner, paler or straw-coloured. Some dogs bleed a lot, some very little, and many clean themselves so well that you see almost nothing.

More licking

Dogs lick the area more during a heat. Persistent licking that seems to bother her is something to mention to your vet.

Changes in the nipples

Nipples can look slightly larger or pinker, but this is a subtle sign and not a reliable one.

Behaviour signs

• Restlessness or clinginess. She may follow you more or seem unsettled.
• Mood changes. Some dogs are more affectionate, others irritable.
• Marking. More frequent urination, with a stronger scent, to advertise her condition.
• Appetite changes. Some eat less during proestrus.
• Attention from male dogs. Males can detect a female in heat from a distance.
• Her own attitude to males. In proestrus she usually refuses to mate, and in estrus she becomes receptive.

In estrus, a receptive female stands still when a male approaches and may move her tail to the side. That is the time she can conceive; see our guide to how long dogs are pregnant for what follows a mating.

How the signs change by stage

Dates are hard to pinpoint by eye. Breeders who need exact timing use progesterone tests with their vet. The Dog Heat Cycle Calculator estimates when the next heat will begin if you know the last start date and interval.

What to do when you notice the signs

1. Note the date. The first day you see swelling or discharge is the start of the heat. Use it with the calculator.
2. Keep her on a lead and in a secure garden. Check gates and fences, because males can arrive from some distance.
3. Supervise outdoors, and take extra care at dog parks and on walks.
4. Manage the mess. Use washable bedding, and wipe up on hard floors. Some owners use dog pants made for the purpose.
5. Keep her routine normal, with gentle exercise.
6. Plan ahead for boarding, since many kennels do not accept dogs in season.

If you want to avoid a litter, the safest approach is to keep her away from intact males for the whole heat, not only the days that seem most fertile, and to talk to your vet about neutering.

A worked example

You notice swelling and a few spots of blood on 1 April.

1. That is day 1 of the heat.
2. Proestrus is expected to last about 9 days, to around 10 April, and estrus about 9 days after that, to around 19 April.
3. The fertile period is mostly in estrus, but timing varies, so you plan to supervise her until the swelling and discharge have gone, usually about 2 to 3 weeks.
4. You note the start date, 1 April, in your record. With a 7-month interval the next heat would be around 1 November.

Signs that are not normal

Contact your vet if:

• She has no heat by 2 years of age.
• A heat lasts more than 4 weeks.
• She has a discharge and seems unwell after a heat, for instance lethargic, drinking more, vomiting or off her food. This can be a sign of a womb infection called pyometra, which is urgent.
• Her cycle suddenly changes, with very frequent or very rare heats.
• She is licking so much that her skin looks sore.

Heat or something else?

Several things can look like a heat: a urinary infection can cause bloody urine, and a vaginal problem can cause discharge. If you are not sure what you are seeing, or if she has been spayed and shows signs, see your vet. Do not treat discharge at home without advice.

Common mistakes

• Assuming a dog is not in heat because there is little blood.
• Letting her off the lead because “it is only the early days”.
• Assuming a dog cannot become pregnant in proestrus.
• Not writing down the start date.
• Ignoring discharge and illness after a heat.
• Believing a dog should have a litter before neutering. There is no veterinary reason for this.

Keeping a heat diary

A diary lets you see the pattern, and it helps your vet if there are questions. A page per heat is enough.

Write the day you first notice swelling or discharge as day 1, and continue until the swelling has gone and she has lost interest in males. After two or three heats you will see how long yours lasts and how heavy the discharge is. The Dog Heat Cycle Calculator predicts the next one from the start date and the interval.

Managing the mess at home

Discharge is not a medical problem in itself but can be a nuisance. Some practical ideas:

• Use washable bedding and put a throw on the sofa.
• Confine her to a part of the house with easy-clean floors, if she is not in the family areas.
• Use dog pants or reusable pads made for the purpose, if she tolerates them, and change them often.
• Wipe with a soft damp cloth rather than strong cleaners, and ask your vet what is safe.
• Wash her bedding and floors with products that are not harmful to dogs.

Do not restrict water, and keep exercise and play normal within safe limits.

Walking a dog in heat

Most dogs in heat can be walked, with care:

1. Keep her on a lead at all times.
2. Choose quiet routes, and go at quiet times of day.
3. Avoid dog parks, fields where off-lead dogs run and training classes.
4. Watch for males approaching, and be ready to move away.
5. Do not leave her tied up outside a shop or alone in a garden with weak fences.
6. Keep her close at home, and do not allow her out unsupervised.

If the household has an intact male dog, plan separate spaces or ask your vet for advice, since keeping dogs apart can be hard.

Stages at a glance

Lengths vary between dogs, so use these as a guide only. The Dog Heat Cycle Calculator uses the same approximate figures. For timing between heats read how often dogs go into heat. If bleeding is heavy, lasts much longer than usual, or she seems unwell, call your vet.

Planning ahead for the next heat

Once you know the start date and the interval, mark the expected next heat on the calendar. Plan boarding, travel and training classes around it, tell your groomer and think about the home set-up. If you do not plan to breed, talk to your vet about whether and when spaying is right for your dog. This is a medical decision that depends on breed, size, age and health, and your vet can explain the options and the timing.

Behaviour changes that are common

Many owners notice more licking of the area, more frequent urination on walks, restlessness, flirty behaviour toward males and sometimes irritability. Appetite can go up or down. Keep routines steady, offer extra attention and avoid stressful new situations. If behaviour changes seem extreme, mention them to your vet.

What heat is not

A heat is not an illness, and bleeding at this time is expected. Bleeding outside the usual pattern, a foul-smelling discharge, a swollen belly, vomiting, drinking much more than usual or lethargy are different, and should be checked promptly. The distinction matters because some serious conditions can follow a heat, so call your vet when you are unsure.

A short checklist for owners

• Note the first day of swelling or discharge.
• Keep her on a lead and away from males.
• Use washable bedding and easy-clean areas.
• Keep exercise gentle and safe.
• Note the end date.
• Calculate the next expected heat with the calculator.
• Call your vet for anything unusual.

Quick summary

1. Signs: swollen vulva, bloody discharge that becomes paler in estrus, licking, mood changes, marking and interest from males.
2. Proestrus lasts about 9 days and estrus about 9 days; she is fertile in estrus but assume risk throughout.
3. Note the first day of swelling or discharge and keep her on a lead.
4. Call your vet for no heat by 2 years, a heat over 4 weeks or illness after a season.
5. Neutering is a decision to make with your vet.
6. Use the Dog Heat Cycle Calculator to predict the next heat.

Frequently asked questions

Sources

1. Merck Veterinary Manual (pet owner version) — Management of Reproduction in Dogs
2. Concannon P.W. (2011) Reproductive cycles of the domestic bitch. Animal Reproduction Science 124:200-210
3. Cornell University College of Veterinary Medicine — Dog estrous cycles

Related calculators

• Dog Heat Cycle CalculatorPredict your dog's next season and the stages of the heat cycle.
• Dog Pregnancy Due Date CalculatorEstimate your dog's due date and the normal whelping window.
• Dog Age CalculatorConvert your dog's age into human years, taking size into account.

Keep reading

• How Long Does a Dog Stay in Heat? StagesA dog's heat usually lasts about 2 to 3 weeks and comes around every 7 months on average. Learn the four stages, how often it happens and when to call the vet.
• How Often Do Dogs Go Into Heat?How often dogs go into heat: about every 7 months on average (range 4 to 12), first heat timing, size differences, how to track dates and a next-heat calendar.
• How to Tell if Your Dog Is PregnantHow to tell if a dog is pregnant: early signs, why they are unreliable, ultrasound from about 25 days, the relaxin blood test, phantom pregnancy and what to do next.
• Dog Heat vs Phantom Pregnancy: What Is Going On?How to tell a dog in heat from a phantom pregnancy: the timeline after a heat, signs of false pregnancy, why only a vet can tell it from real pregnancy.