Your unspayed female dog will go through two to three heat cycles on average per year.  Being in heat is the most common reason for vaginal bleeding, but there are other medical conditions that may cause your dog to bleed from her vagina.  You should try to determine if the bleeding originates from the vagina or is in your dog’s urine.  Additionally, your dog may eliminate bloody diarrhea, which may appear to come from her vagina.  

Possible causes of a bloody discharge include:

There are a few reasons why your dog may be bleeding from her vagina (vulva).  Blood in the urine may indicate a urinary tract infection but differs from blood that passes from the vulva and is usually present within a voided urine sample.

Unspayed females will go through two to three estrus cycles annually, also known as 'going into heat'.  A heat cycle lasts two to three weeks and begins as spot bleeding from the vulva.  Your dog’s vulva will also become swollen, and she may urinate more often than normal.  Her excessive urination is meant to attract male dogs.  Estrus cycles are not a medical condition but a natural reproductive cycle in dogs.

Pyometra is a medical condition that may arise during or, more typically, after, an estrus cycle and is an infection in the uterus.  Pyometra is a serious, life-threatening condition that requires immediate medical treatment.  As your dog’s hormones change during her heat cycles white blood cells, which prevent infection, are not permitted into the uterus.  The uterine lining will grow in anticipation of pregnancy.  However, if pregnancy does not occur within several consecutive heat cycles, cysts can start to grow within the thickened tissue and create an ideal environment for bacterial growth. Without the white blood cells present to combat the bacterial growth, your dog can develop a uterine infection.

Your dog may become pregnant during her estrus cycle, and after a few weeks, her body may abort the pregnancy due to a number of reasons.  Miscarriages will often result in excessive bleeding from the vagina where your dog may pass the placenta and other tissues.

If your spayed female is experiencing vaginal discharge that contains blood, she may be suffering from vaginal inflammation or vaginitis. Additional symptoms of vaginitis include frequent urination or difficulty urinating.  Your dog may also lick her vulvar area more frequently and scoot her bottom across the floor.  Vaginitis is usually caused by an infection or foreign body and can affect any female at any age although prepubescent and older dogs appear more predisposed. 

Unspayed females are more likely to develop vaginal tumors as they age. Most vaginal tumors are benign, or non-cancerous and can cause vulvar bleeding as well as blood in the urine, vaginal odor, and difficulty giving birth. 

You should take you dog to the veterinarian if she is bleeding from her vagina and you believe she is not in heat.  Your vet will perform a complete physical examination and ask you when you first noticed her symptoms.  The vet will also ask you about the quantity and quality of her bleeding; for example, if your dog is spotting or hemorrhaging and if the blood is thick, thin, or accompanied by other discharge.  The answers to these questions will help your veterinarian make a diagnosis, but additional testing may also be conducted to rule out other conditions.  

Your veterinarian may take a vaginal swab to test for bacterial infections associated with urinary tract infections or vaginitis.  Tissue samples collected from your dog’s vulva may also be examined to determine if any tumors may be present.  If your vet finds tumor growth, a CT scan or X-ray will be ordered to determine location, size, and possible metastases.  Typically, surgery is conducted to remove the uterus and ovaries as well as the tumor growth.  Radiation and chemotherapy may be utilized to destroy any hidden cancer cells and prevent a reoccurrence of tumor growth.  Dogs are far more tolerant of chemotherapy than humans are and experience less illness and hair loss.  However, some breeds of dog are more susceptible to hair loss, including English Sheepdogs, Lhasa Apsos, Maltese, Schnauzers, Shih Tzus, and Poodles.

Many of the medical conditions associated with bleeding from the vagina can be prevented by spaying your dog.  Spaying your dog will also end future estrus cycles and prevents contribution to the dog overpopulation.  Pyometra results from hormone changes associated with consecutive estrus cycles not resulting in pregnancy.  The treatment for pyometra is usually an ovariohysterectomy (spay), but this can be a complicated surgical procedure when your dog is fighting a bacterial infection.

Bacteria can also grow in the urinary tract and infect your dog.  Giving her access to clean water and the opportunity to eliminate her waste frequently will help prevent bacterial infections that might lead to vaginal inflammation.  

Unfortunately, you may not be always able to prevent tumors from growing in your dog’s vagina, but early spaying can significantly reduce the risk of developing tumor growths and cancer later in life. Transmissable Venereal Tumors (TVTs) can be spread via sexual contact with an infected male. This type of cancer usually responds well to chemotherapy.

The cost of treatment for your dog’s bleeding from her vagina depends on the underlying medical condition.  For example, treatment for vaginitis can cost around $200-400 whereas pyometra can cost around $1,200-$3,000.  Treatment for caner can cost between $4,000- $7,500 depending on how extensive it may be when diagnosed.