A female dog in heat needs extra supervision, hygiene management, and comfort for roughly two to three weeks. The experience can be stressful for both of you, especially the first time, but with some straightforward adjustments to your routine, you can keep her safe, comfortable, and out of trouble until the cycle passes.
When Heat Starts and How Long It Lasts
A dog’s first heat can start anywhere between 6 and 24 months of age, with smaller breeds typically cycling earlier and larger breeds later. Most dogs go into heat about twice a year, though giant breeds may only cycle once annually. The full heat cycle spans several weeks and moves through distinct phases: a lead-in period with swelling and bloody discharge (proestrus), the fertile window when she’ll accept a mate (estrus), and a longer hormonal wind-down afterward. The portion you’ll actively manage, the bleeding and behavioral changes, generally lasts around two to three weeks total.
Signs Your Dog Is in Heat
The first thing you’ll notice is a swollen vulva and bloody or pinkish discharge. Some dogs bleed heavily enough to leave spots around the house, while others keep themselves clean enough that you barely notice. As the cycle progresses, the discharge often lightens in color and becomes thinner, which signals she’s entering her most fertile days.
Behaviorally, expect noticeable changes. She may become more skittish or unusually aggressive around people and other animals. Some dogs get clingy, others restless. When she’s around other dogs, she may try to mount them or allow herself to be mounted. If no other dogs are around, she might try mounting your legs. Once she’s fully in estrus, you’ll likely see “flagging,” where she curls her tail to the side. This is her signal to male dogs that she’s ready to mate, and it means you’re in the highest-risk window for an unplanned pregnancy.
Preventing Unplanned Mating
This is the single most important thing to manage. Male dogs can detect a female in heat from a surprisingly long distance, and they will go to extraordinary lengths to reach her, including jumping fences, digging under gates, and slipping through doors.
Keep your dog on a leash for every outdoor trip, even in a fenced yard. A fenced yard that’s normally secure may not be enough, because male dogs in the neighborhood will be drawn to the area. Walk her at off-peak times and avoid dog parks entirely. If you have an intact male dog in the same household, separate them completely. Depending on the size of your home, keep them in different rooms or on opposite sides of the house. Even a closed door may not be sufficient if the male is determined, so consider boarding one of the dogs or having one stay with a friend or family member for the duration.
Regular cleaning helps reduce the scent that attracts males. Clean up any discharge promptly and wash bedding or fabrics she’s been in contact with using a pet-safe detergent. This won’t eliminate the pheromone signal entirely, but it reduces how far the scent carries.
Managing Discharge and Keeping Things Clean
Some owners let their dogs manage the discharge by licking, which many dogs do naturally. Others use dog diapers or washable belly bands designed for females in heat. If you go the diaper route, change them frequently to prevent irritation and infection. A damp cloth works well for quick cleanups of her fur and hindquarters.
Cover furniture and bedding with old towels or washable blankets during the cycle. Restrict her access to carpeted rooms if the discharge is heavy. Some dogs bleed very little, so you may find this is less of an issue than expected. Either way, having a designated resting area with easy-to-wash coverings makes the whole process more manageable.
Keeping Her Comfortable
Many dogs in heat feel off. They may eat less, seem tired, or act anxious. Give her a quiet, comfortable space where she can retreat when she wants to be left alone. Extra attention and calm interaction help, but follow her lead. If she wants to curl up and sleep, let her. If she’s restless and wants to play, gentle indoor activity can burn off some of that nervous energy.
Appetite changes are common. Some dogs eat less during the first week and then bounce back. Keep her on her regular diet and don’t worry too much about a temporary dip in food intake. Make sure she has constant access to fresh water, as hormonal changes can increase thirst. If she refuses food for more than a day or two, or seems genuinely unwell rather than just “off,” that warrants a closer look.
Health Risks to Watch For
The most serious complication linked to the heat cycle is pyometra, a bacterial infection of the uterus that typically develops one to two months after a heat cycle ends. It’s not something that happens during heat itself, but it’s a direct consequence of the hormonal changes that occur, and it’s life-threatening if untreated. Watch for vaginal discharge that’s cream-colored or bloody outside of a normal heat cycle, lethargy, poor appetite, increased thirst and urination, a swollen or painful belly, vomiting, fever, or pale gums. If you see any combination of these signs in the weeks following heat, get to a vet immediately. Pyometra almost always requires emergency surgery.
False pregnancy is another post-heat possibility. After the cycle ends, some dogs develop physical and behavioral signs that mimic pregnancy: mammary enlargement, milk production, nesting behavior, restlessness, decreased appetite, and even maternal behavior toward toys. This is hormonally driven and typically resolves on its own within a few weeks without treatment.
Spaying After the Cycle
If you don’t plan to breed your dog, spaying eliminates future heat cycles and dramatically reduces the risk of pyometra and mammary tumors. Most vets recommend waiting until the heat cycle is fully over before scheduling surgery, because the increased blood flow to the reproductive organs during heat makes the procedure riskier. The typical recommendation is to wait two to three months after the end of heat. Talk to your vet about the right timing for your dog’s breed and age, since recommendations for large breeds sometimes differ from those for smaller dogs.
Until then, you’ll need to manage each cycle as it comes. The good news is that most owners find the second heat much easier than the first, simply because they know what to expect and have a routine in place.