If your female dog is not spayed, she will go into heat at some point — and if it is your first time seeing it, it can feel a little confusing. One day she seems completely normal, and the next she is clingy, restless, and leaving small spots on the floor. Do not worry. Going into heat is a natural part of a healthy dog’s life, and once you know what to look for, it becomes much easier to handle.
In this guide, we will walk through the early signs of heat, what each stage looks like, and simple ways to keep your dog comfortable and safe.
What Does “Going Into Heat” Actually Mean?
Going into heat, also called estrus, is the time when a female dog’s body becomes ready for breeding. During this period, her body releases hormones that cause physical and behavior changes. Most dogs go into heat about twice a year, although this can vary by breed, age, and size.
Small dogs often have their first heat between 6 and 10 months of age, while larger breeds may start between 12 and 18 months. After that, most dogs settle into a pattern of roughly every 6 to 8 months.
A full heat cycle usually lasts around 2 to 4 weeks, happening in stages, with your dog’s behavior and body changing as she moves through each one.
The Early Signs: How to Tell She Is About to Start
The earliest signs can be subtle, and they often show up a few days before any obvious bleeding begins. If you notice several of these changes together, there is a good chance your dog is going into heat.
1. Her Vulva Looks Swollen
One of the first physical signs is swelling around the vulva, the external area under her tail. It may look larger and puffier than usual, and the skin may appear slightly redder. This swelling usually starts before bleeding and can last through much of the cycle. It is a normal part of the hormonal changes happening in her body.
2. Light Spotting or Bleeding
A small amount of bloody discharge is one of the most well-known signs of heat. At first, the discharge may be light pink or red, and it may appear as tiny spots on her bedding, the floor, or your furniture. Some dogs are very clean and lick themselves often, so you may barely notice it. Others leave more obvious spots. Either way, light spotting is normal during the early part of the cycle.
The color and amount of discharge change over time. It often starts red, then becomes lighter pink or straw-colored as the cycle goes on. A sudden change to very dark, thick, or foul-smelling discharge is not typical — see the vet section below.
3. She Is Urinating More Often
A dog in heat will often urinate more frequently, especially on walks. This is not an accident or a house-training problem. Her urine contains pheromones, which are natural scent signals that tell male dogs she is in heat. She may stop to mark small amounts in many different spots rather than emptying her bladder all at once.
If your dog suddenly needs more bathroom breaks, be patient with her. Let her out more often, and do not scold her for the extra trips. She is following a strong natural instinct.
4. Her Behavior Changes
Behavior changes are often the first thing owners notice, even before any physical signs. Your dog may become more affectionate and clingy, following you from room to room and asking for extra cuddles. On the other hand, some dogs become more restless, anxious, or easily distracted.
You may also notice she is less interested in her usual games, or more alert on walks. Some dogs become a little moody, especially if touched near their back end. These mood swings are caused by hormones and usually settle once the cycle is over.
5. Male Dogs Suddenly Pay Her a Lot of Attention
If male dogs in the neighborhood suddenly seem very interested in your dog, that is a strong sign she is in heat. They can smell her pheromones from a surprising distance, and they may whine, follow her, or try to get close. Even dogs that normally ignore her may become persistent.
This is why walks and outdoor time need extra care during heat — a determined male dog can be hard to keep away.
6. She Is Licking Herself More Than Usual
Increased licking around the vulva is another common early sign. Your dog may groom herself more often to stay clean, especially once spotting starts. This is normal self-care behavior. However, if the licking becomes constant or obsessive, or if the area looks sore or irritated, it is worth keeping a closer eye on it.
7. Changes in Appetite and Energy
Some dogs eat a little less during heat, while others seem hungrier than usual. Energy levels can shift too. Your dog might be more playful and excitable one day and sleepy and withdrawn the next. Small changes in appetite and energy are normal during a heat cycle, as long as she is still eating, drinking, and moving around.
The Stages of a Heat Cycle, Explained Simply
A heat cycle has four stages, but most owners only need to understand the first three in detail:
Proestrus (about 7 to 10 days): This is the beginning. The vulva swells, bleeding starts, and male dogs become interested, but your dog will usually not accept a male yet. She may actually snap or move away from them.
Estrus (about 5 to 14 days): This is the fertile period. The discharge often becomes lighter in color, and your dog may become more willing to accept male dogs. She may stand still and move her tail to one side when a male approaches. This is the stage when pregnancy is possible, so supervision is most important here.
Diestrus (about 2 months): The discharge stops, the swelling goes down, and her behavior returns to normal. Her body is either recovering from the cycle or, if she was bred, preparing for pregnancy. Even if she was not bred, some dogs show mild signs like nesting behavior or swollen mammary glands during this stage.
Anestrus: This is the quiet rest period between cycles, when her hormones settle back to normal. It usually lasts several months.
How to Take Care of Your Dog During Heat
Once you know your dog is in heat, a few simple steps will make life easier for both of you.
Keep Her Comfortable at Home
Washable dog diapers or reusable heat pants can help protect your furniture and floors from spotting. Make sure the diaper fits well — not too tight — and change it regularly so her skin stays clean and dry. Some dogs dislike diapers at first, so let her get used to them indoors for short periods before expecting her to wear one all day.
Keep Walks Short and Supervised
Always keep your dog on a leash during heat, even in a fenced yard if there is any chance a male dog could get in. Avoid dog parks and off-leash areas entirely for the full cycle — it only takes a moment for an unplanned mating to happen, and it can be stressful and even dangerous for your dog.
Watch Her Eating and Drinking
Offer her normal food and fresh water as usual. If her appetite drops a little, do not panic, but a dog that stops eating completely or refuses water for more than a day should be checked by a vet. For younger dogs, our guide on how much to feed your puppy by age and weight is a useful reference.
What NOT to Do When Your Dog Is in Heat
Do Not Let Her Roam Unsupervised
This is the single most important rule. Even a normally obedient dog may wander or escape during heat because of strong hormonal urges. A secure yard, a closed gate, and a leash on every outing are essential. Never leave her alone in the yard for long periods during her cycle.
Do Not Punish Her for Natural Behavior
Extra urination, clinginess, restlessness, and moodiness are not bad behavior — they are hormones at work. Scolding her will only add stress. Instead, stay patient, keep routines steady, and give her extra reassurance.
Do Not Give Her Medication or Supplements Without Vet Advice
You may hear about products that claim to stop or delay heat, or calm a dog down during her cycle. Do not use any of these without talking to your vet first. Some hormone treatments can have serious side effects, and what works for one dog may not be safe for another. If you are considering spaying or want to manage future cycles, a conversation with your vet is the safest first step.
Do Not Assume the Cycle Is Over Too Early
Many owners relax too soon. Bleeding may stop before the fertile period ends, and your dog may still attract males for days after the discharge fades. Keep up the supervision until the swelling is fully gone and her behavior is back to normal for several days. When in doubt, wait a few extra days before returning to dog parks or off-leash walks.
Do Not Ignore Unusual Symptoms
Normal heat has a pattern: swelling, light discharge, behavior changes, then a gradual return to normal. Anything outside that pattern — heavy bleeding, bad-smelling discharge, fever, vomiting, or extreme lethargy — is not something to wait out at home. Trust your instincts: if something feels wrong, it is always better to call the vet.
When to See a Vet
Most heat cycles pass without any problems, but there are times when a vet visit is the right call. Contact your vet if you notice any of the following:
- Very heavy bleeding, large clots, or bleeding that lasts longer than 4 weeks
- Discharge that is thick, yellow, green, or has a strong, foul smell
- Fever, vomiting, loss of appetite for more than a day, or unusual tiredness
- Excessive thirst or urination that continues after the cycle ends — this can be a sign of a serious womb infection called pyometra, which needs urgent treatment
- Swelling or redness that becomes painful, or sores around the vulva
- A heat cycle that is very irregular, missing entirely, or happening much more often than every few months
Regular vet checkups also help you stay on top of her reproductive health — our guide on how often to take your dog to the vet by age breaks it down simply.
If you notice other changes in her body after the cycle, our article on early signs your dog may be pregnant can help you tell the difference between normal post-heat recovery and a possible pregnancy.
Frequently Asked Questions
How long does a dog stay in heat?
Most dogs stay in heat for about 2 to 4 weeks. Bleeding usually lasts 7 to 14 days, but the full cycle can take up to a month. Keep her supervised for the whole period, not just while she is bleeding.
At what age do dogs have their first heat?
Small breeds often have their first heat between 6 and 10 months, while larger breeds may start between 12 and 18 months. Giant breeds can start even later. If your dog has not had a first heat by 2 years of age, mention it at her next vet visit so it can be checked.
Can a dog get pregnant on her first heat?
Yes, it is physically possible, but it is not recommended — a dog having her first heat is still growing herself, and early pregnancy carries extra health risks for mother and puppies.
How often will my dog go into heat?
Most dogs go into heat about twice a year, roughly every 6 to 8 months. Young dogs can be irregular at first, and a big change in your dog’s usual pattern is worth mentioning to your vet.
Should I spay my dog, and when is the best time?
Spaying stops heat cycles completely and prevents unwanted pregnancies and some serious health problems, including pyometra. The best timing depends on your dog’s breed, size, and health, so talk to your vet about what fits your individual dog.
A Final Word
Seeing your dog go into heat for the first time can feel overwhelming, but it is a normal, healthy part of her life. Once you recognize the signs — swelling, light spotting, extra trips outside, clinginess, and sudden attention from male dogs — you will know exactly what is happening.