Female dogs going through their heat cycle typically become more restless, clingy, and attention-seeking than usual. The whole cycle lasts about three weeks, and your dog’s behavior will shift noticeably at each stage, from playful flirtation with male dogs early on to active attempts to find a mate during peak fertility. Understanding these changes helps you know what’s normal and what to watch for.
Early Signs: The First Week or So
The heat cycle starts with a phase called proestrus, which generally lasts 7 to 10 days. During this time, your dog’s vulva swells and she begins producing a bloody discharge. She may lick herself more frequently and seem distracted or unsettled. Male dogs will start showing intense interest in her, but she won’t be receptive yet. She may snap at or avoid males who approach, or she might engage in playful behavior without actually allowing mating.
This early phase is when many owners first notice personality changes. One of the most common signs is increased clinginess or attention-seeking. Your dog may follow you from room to room, nudge you for affection more than usual, or seem generally restless. Some dogs also become mildly irritable or moody, showing less tolerance for other pets in the household or acting uneasy in unfamiliar settings.
Peak Fertility: When Behavior Changes Most
After the initial phase, your dog enters estrus, the stage when she’s actually fertile and receptive to mating. This is the period of the most dramatic behavior shifts. Where she previously rejected male dogs, she now actively seeks them out. She may “flag” her tail to the side, present her hindquarters, and become unusually eager to get outside. Roaming behavior spikes during this window, and even well-trained dogs may try to escape yards or bolt through open doors.
The actual fertile window within this stage is surprisingly short. Her eggs are only viable for fertilization for about 2 to 3 days during the entire heat cycle. But because sperm can survive in the reproductive tract for several days, the risk period is wider than that narrow window suggests. Dogs in estrus often become more vocal, whining or barking more than usual, and may seem unable to settle down. Appetite changes are common too. Some dogs eat less during this phase, while others seem unaffected.
Winding Down: After the Fertile Phase
Once estrus ends, your dog enters a phase where she’s no longer receptive to males and will reject their advances again. The discharge tapers off, vulvar swelling decreases, and her personality gradually returns to baseline. Most dogs settle back into their normal routine within a few days of this shift, though hormonal changes continue internally for weeks. Some dogs go through a sort of “false pregnancy” after their cycle, nesting with toys or showing maternal behaviors even without being pregnant.
What the Whole Cycle Looks Like
Most unspayed female dogs go into heat roughly every six months, though this varies by breed and size. Small breeds may cycle more frequently, while some large breeds only go into heat once a year. The first heat typically arrives between 6 and 12 months of age for smaller dogs and can be delayed until 12 to 24 months for giant breeds. Cycles can be irregular at first and may take a year or two to settle into a predictable pattern.
A summary of what you’ll likely see across the full cycle:
- Restlessness and clinginess: Following you around, seeking extra affection, pacing, or seeming unable to relax.
- Irritability with other animals: Less patience with housemates, occasional snapping or growling at other pets.
- Increased vocalization: More whining, whimpering, or barking than usual.
- Roaming and escape attempts: Strong drive to get outside and find a mate, especially during peak fertility.
- Appetite changes: Eating less than normal or showing inconsistent interest in food.
- Excessive licking: Frequent grooming of the genital area in response to discharge.
Managing the Mess and Keeping Her Comfortable
The bloody discharge during heat can range from light spotting to enough to stain furniture and bedding. Dog diapers are the most practical solution for keeping your home clean. You can line reusable diapers with a disposable feminine hygiene pad for extra absorbency, replacing just the pad instead of the whole diaper each time. Change the diaper whenever it’s soiled, and check that the skin underneath isn’t staying damp, since prolonged moisture can lead to yeast or bacterial growth. Using pet-safe wipes or a waterless shampoo between changes helps keep things clean.
Remove the diaper when you take your dog outside to potty, and give her diaper-free breaks every few hours so her skin can breathe. If she seems stressed by the diaper, try introducing it gradually with treats and praise. Some dogs tolerate them easily, while others need a day or two to adjust. Covering her usual resting spots with washable blankets is another simple way to manage staining.
One Serious Risk to Know About
Pyometra is a life-threatening uterine infection that typically shows up two to four months after a heat cycle. It happens when bacteria take hold in the uterus during the hormonal changes that follow estrus. The early signs are subtle: increased thirst, more frequent urination, and lethargy. Some dogs develop a foul-smelling vaginal discharge that ranges from pus-like to bloody, while others show no discharge at all, only a distended abdomen.
Without treatment, pyometra can progress to sepsis, kidney damage, or uterine rupture. Dogs with a closed form of the infection, where nothing drains from the uterus, tend to get sicker faster and face a higher risk of sepsis. If your unspayed dog seems unusually lethargic, is drinking excessively, or loses her appetite in the weeks following a heat cycle, that combination warrants urgent veterinary attention. Pyometra is the most common serious complication of the intact female reproductive cycle, and it becomes more likely with each successive heat.