1. Depending on the breed of dog, the age at which it goes into heat will vary. Generally speaking, they will reach sexual maturity between six months and one year old after birth, and they can become pregnant and breed when they are one to one and a half years old. Male dogs have the ability to reproduce after reaching sexual maturity between six months and one year old.

　2. The range of activities becomes larger, restlessness, emotional instability, drinking a lot of water, and urinating bit by bit everywhere, leaving a smell.

3. Some people call vaginal bleeding "menstruation", but this is just the opposite of humans. Female dogs menstruate to get pregnant. A dog's menstruation is about 7 to 10 days after the estrus period. The amount of bleeding varies among individuals, and some small dogs will even ignore it without paying attention.

　4. Like humans, dogs will also feel uncomfortable during their menstrual period. Especially in the first few times, they will usually feel depressed, not want to eat, not like to do activities, etc. A menstrual period lasts for about two weeks. If there is nothing other than not eating very much, you can think that there is nothing wrong.

5. Dogs will have stomachaches and loss of appetite when they are on their period. Rubbing their stomachs will make them feel better. In addition, you can give it some light, easy-to-digest and nutritious food. If you are still not eating after your period, you should go to the pet hospital for a checkup.

6. Female dogs have periodic estrus, which lasts until they become old dogs. When in estrus, there is usually a slight amount of blood. If the amount is large, it may be endometritis or pyometra. In severe cases, it may be endometritis or pyometra. May be fatal, please be careful.