Do Dogs Have Periods?

Understanding the female canine’s menstruation (heat) cycle.

Wondering about questions like, “Do female dogs have periods?” might seem like an odd thought to have. Yet, for un-spayed female dog owners, this thought may have crossed their minds at least once after seeing their beloved fur kid discharge blood from their vaginal cavities.

So, the question remains, do female dogs have periods? Simply put, the answer is “technically speaking, no.”

But to understand why vaginal discharge occurs with canines begins with understanding the anatomy of their bodies. While mammals (including humans and dogs) share the same basic reproductive organs, the way these organs function differ from one species to the other.

Firstly, it should be clarified that humans go through the menstrual cycle while dogs go through the oestrous cycle.

With female humans, the uterus will build up on nutrients in anticipation for potential foetus growth; if an egg goes unfertilised at the end of the month, the uterus lining is then secreted from the body through bleeding — concluding the fertility cycle.

With canines, however, if an egg goes unfertilised, the nutrients are re-absorbed by the body over a period of time. The vaginal discharge displayed by female dogs thus comes from the vagina and not from the uterus because it serves several functions; one of which being a signal for the onset of fertility. This is also commonly known as the “heat” cycle.