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Heat Cycles in Unaltered Dogs

Female dogs can begin a heat cycle as early as six months of age. During this time, her urine contains hormones and pheromones easily detected by male dogs from great distances. The typical intact female experiences two cycles per year, each lasting approximately two to three weeks, and this is the only time she can get pregnant.

Physical and behavioral signs of a heat cycle include:

  • Swollen vulva
  • Bloody discharge
  • Flagging of the tail to the side
  • Frequent urine-marking

Safety precautions:

  • Always supervise your female dog outdoors when she is in heat, even while in a fenced-in yard. Male dogs will become interested and have been known to dig or jump fences to mate. 
  • Avoid walking if there are loose dogs or dogs behind invisible fences in your neighborhood for this three-week period. 
  • Close windows to minimize the flow of pheromones.
  • If you have an unaltered male in the same house, you must physically separate them with a door or secured, tall baby gate. Do not crate them side by side, as this will cause stress and frustration. Ideally, they should avoid sharing spaces at all. Use different entryways, rest spots, and potty areas. 
  • There will be bloody discharge. Some dogs clean and maintain their vulva better than others. If needed, use female dog diapers and change them throughout the day. You may also put sanitary pads inside of the dog diaper to extend the life of each diaper. Laying potty pads on couches, bedding, or any furniture your dog goes onto will assist in easy cleanup. 
  • Your dog is going through changes in hormone levels; they may be physically uncomfortable and experience behavior changes. It will be important for you to give her space, time, and extra mental enrichment to help her feel comfortable. 
  • To stop future heat cycles entirely, visit for spay/neuter services near you.