Generally speaking, the menstrual time of dogs is 6-14 days, and it can reach 21 days if it is longer, but it generally does not last 40 days, so it is recommended to take the dog for a B-ultrasound examination when this happens. Check to see if there are any abnormalities in the uterus. Urinalysis and urine sediment must also be done. Cystourethritis can also cause blood in the urine. It must be abnormal for such a long menstrual period.

Dogs usually menstruate for 6-14 days each time

Dogs go into estrus twice a year, usually from March to May in spring and September to November in autumn. Female dogs go into estrus. At this time, characteristic symptoms occur in the body and behavior. It mainly manifests itself in the following stages.
①Pre-estrus. It is the preparation stage for estrus, which takes about 7-10 days. The reproductive system begins to prepare for ovulation. The egg is close to maturity, the reproductive tract epithelium begins to proliferate, glandular activity begins to intensify, secretions increase, the vulva is congested, the vulva is swollen, flushed, wet and lubricated, and mucus mixed with blood flows. Male dogs often come after smelling it, but female dogs are not allowed to mate.
② Estrus period. This is the period when signs of estrus are most obvious and mating is accepted, lasting about 6-14 days. The vulva continues to swell and soften, the mucus flowing out becomes lighter in color, and the bleeding decreases or stops. The female dog takes the initiative to approach the male dog. When the male dog climbs up, she takes the initiative to step down on her waist, face the male dog with her buttocks, tilt her tail to one side, and open her vulva to allow mating. 2-3 days after estrus, the female dog begins to ovulate, which is the best time for mating.
③ Late estrus. The swelling of the vulva subsided and gradually returned to normal. Her temperament became quiet. She was not allowed to become quiet and male dogs were not allowed to approach. It usually lasts for two months and then enters the anestrus period. If you are pregnant, the period after estrus is the pregnancy period.