How Often Do Dogs Go Into Heat?

The short answer: most dogs come into heat about every six months — roughly twice a year. The honest answer: the range across normal, healthy dogs runs from three heats a year down to just one, and the single biggest factor is the size of the dog.

Cycle Frequency by Size

• Small and toy breeds cycle most often. Every four to six months is common, which can mean up to three heats in a calendar year for some individuals.
• Medium and large breeds are the textbook case: a heat roughly every six months.
• Giant breeds — Great Danes, Mastiffs, Saint Bernards and friends — often cycle only every eight to twelve months. A single heat per year in a healthy giant-breed girl is completely normal.
• Primitive and basal breeds are their own story. Basenjis famously cycle just once a year, typically in autumn, and a few other landrace-type breeds behave similarly.

The reason for the variation is mostly the length of anestrus, the resting stage between cycles. The visible heat itself lasts about the same two to four weeks regardless of breed — the gap between heats is what stretches. Our complete heat cycle guide walks through all four stages.

"How Often Do Dogs Get Their Period?" — Why That's a Different Question

A lot of people search for dog "periods," and it's worth clearing up because the difference matters practically. Human menstruation happens when a non-pregnant cycle sheds the uterine lining — bleeding marks the infertile end of the cycle. A dog's bleeding happens at the start of her cycle, during proestrus, as she approaches fertility.

So a dog bleeding isn't "on her period" and out of commission — she's a week or two away from the most fertile days of her cycle. Confusing the two is how accidental litters happen, and it's also why the question of whether a dog can get pregnant when not in heat comes up so often. Dogs also don't get monthly cycles — twice a year is the norm — and they don't have menopause, though cycles do slow down with age (see when dogs stop going into heat).

Individual Consistency Beats Breed Averages

Here's the part that matters most for breeders: whatever your dog does is her normal. A healthy bitch tends to be remarkably consistent with herself — if her last three cycles came at seven-month intervals, plan on seven months, not on the six-month textbook figure.

That consistency is what makes record-keeping genuinely predictive. Log the first day of every heat, and after two or three cycles you'll project the next one within a week or two. That's exactly the math our free dog heat cycle calculator runs: last heat date plus her typical interval, out to the next several expected seasons.

When "Often" Becomes "Too Often" (or Too Rare)

Worth a veterinary conversation:

• Cycles closer than every 4 months. Some small-breed girls do this normally, but frequent cycling can also indicate the ovaries aren't completing a normal cycle, and short interestrous intervals are associated with reduced fertility. A repro vet can confirm whether she's ovulating normally.
• More than 12 months between cycles in a non-giant, non-primitive breed — or a previously regular dog whose cycles suddenly space out. Thyroid issues are one common culprit.
• No first heat by around 18–24 months. See our article on when dogs have their first heat for what's normal by breed size.

Also remember that a "missed" heat sometimes isn't missed at all — it's a silent heat with signs subtle enough that nobody noticed. Before assuming a medical problem, ask whether anyone was actually watching for it, or whether the male dogs in the household were suddenly very interested for a week.

The Breeder's Takeaway

Twice a year is the rule of thumb; your own dog's history is the real answer. Track every heat's start date, project the next one with the heat cycle calculator, and put the expected window on your calendar months ahead — that's when progesterone testing, stud arrangements, and travel plans all become easy instead of frantic. Breeders Companion keeps those heat histories per dog right alongside your litters and breeding calendar, so the pattern builds itself.

This article is for general education, not veterinary advice. If your dog's cycle pattern changes or concerns you, talk to your veterinarian.