Female dogs can have their first heat cycle anywhere between 4 and 24 months of age, but on average, the first heat begins at around 6 months of age. However, the timing of a dogs first heat can vary depending on the dogs size and breed. Smaller breeds tend to have their first heat cycle at an earlier age, while large and giant breeds may not come into heat for the first time until they reach 18 to 24 months of age.

Female dogs who have not been spayed go into heat twice a year, around every 6 months, and each heat cycle lasts around 18 days, for generally anywhere from 2 to 3 weeks. However, its important to note that the exact frequency of estrus depends on the dogs size, breed, and age. During heat, female dogs are receptive to mating and can get pregnant.

Its important to keep track of your dogs heat cycle, especially in the beginning, as it can take up to two years for a female dog to develop regular cycles. Signs of estrus include a swollen vulva, blood-tinged discharge, and behavioral changes such as being more nervous or distracted than usual. If youre not planning to breed your dog, spaying is the best way to avoid pet pregnancy and the whole heat cycle.