Signs Your Dog Is in Heat & How to Manage Them

Recognizing the Signs of Heat in Dogs

Your female dog may enter heat as early as six months old, though it typically occurs between six and fifteen months. The first sign is often a noticeable swelling of the vulva. This is soon followed by a bloody vaginal discharge, which starts dark and becomes clearer and more watery as the cycle progresses. Some dogs bleed heavily and leave trails, while others clean themselves so thoroughly that the bleeding goes unnoticed.

You may also observe behavioral changes. During proestrus, the first stage lasting about nine days, your dog may become more active, restless, and wander more than usual. She may drink and urinate more frequently—this urine carries a strong scent that attracts male dogs from a distance. Despite this, she will reject all advances from males, often growling, snapping, or running away.

When Is She Fertile? Understanding the Cycle

The fertile stage, called estrus, begins when the discharge becomes clearer and more watery—typically around the second day of this phase. Estrus lasts between 3 to 11 days, though the entire heat cycle can last up to four weeks. During this time, your dog may accept male advances.

It’s important to know that bleeding is not a reliable sign of fertility. Some dogs can become fertile as early as seven days after the first blood appears, while others may not be fertile until 23 days in. Without progesterone testing, you cannot accurately predict when your dog is fertile. Therefore, it’s safest to assume she is fertile for the entire heat cycle.

Managing Heat: Practical Steps for Owners

To prevent unwanted breeding, take proactive steps. Use washable doggy diapers—ideally introduced before heat begins so your dog adjusts. Place a white bath rug in her crate to help spot any blood. Even if she’s clean, the scent of her discharge can attract male dogs from far away.

Avoid walking your dog in public during heat, as male dogs may follow her scent and attempt to breach fences or dig under barriers. Some have been known to tunnel under decks or jump over eight-foot fences. Never leave her unsupervised in an open yard or garden, even if it seems secure.

Risks Beyond Unwanted Pregnancy

Besides unintended breeding, the biggest health risk to an intact female is pyometra—an infection of the uterus that can be life-threatening. This is why many owners choose to spay their dogs, especially if they do not plan to breed.

Even neutered male dogs can still detect and be attracted to a female in heat. As one owner noted, her neutered dog became obsessed with a female in heat, showing mounting behavior and constant attention. This shows that scent and instinct remain strong, even without reproductive organs.

Final Tips for a Smooth Heat Cycle

The heat cycle usually lasts about 21 days, divided into proestrus (non-fertile), estrus (fertile), and diestrus (non-fertile). While it may seem like a lot of effort, most owners find it goes by “pretty effortlessly” with proper planning.

Be vigilant, especially during the first few weeks. Keep a close eye on your dog’s behavior and hygiene. If you notice unusual licking, restlessness, or male dogs showing intense interest, it’s likely she’s in heat. With awareness and preparation, you can manage the cycle safely and comfortably.