Reasons for dogs not bleeding during menstruation:

1. Some dogs may have very little menstrual bleeding, and they have already been licked off before their owners notice it. Some dogs may not even bleed.

2. Dogs will bleed during the estrus period, so vaginal bleeding in dogs means that the dog’s estrus period has arrived.

3. It may be because there is a problem with the dog’s uterus or ovaries. You should seek medical treatment in time to avoid delaying treatment.