Ovulation and Progesterone Timing

What you need to know

When it comes to breeding, timing is everything, and understanding the intricacies of your dog’s reproductive cycle is essential for a successful outcome. Ovulation and progesterone timing play pivotal roles in determining the most fertile window during your dog’s heat cycle. Let’s delve into the science behind it.


Estrogen is the hormone responsible for the telltale signs of heat in female dogs. It causes vulvar swelling, bleeding, and vaginal changes. While estrogen levels rise before ovulation, the wide variability in this timing makes it a rough estimate of fertility.

Luteinizing Hormone (LH)

LH is the hormone that triggers ovulation. It remains at low levels until it suddenly surges, signaling the imminent release of eggs. Ovulation occurs approximately two days after this surge, and the eggs become fertile within four to seven days.


Rising Progesterone: Progesterone levels are initially low but rise gradually as the heat progresses. This hormone remains elevated for about 8-9 weeks, regardless of pregnancy. A sharp drop in progesterone marks the end of pregnancy, initiates labor, and can lead to symptoms of false pregnancy in dogs.

Ovulation Timing with Progesterone: To pinpoint the fertile window accurately, veterinarians examine the rise in progesterone levels. The initial increase aligns with the LH surge and occurs within a day or two. Progesterone reaches around 5.0 on the day of ovulation and ideally falls within the 8.0 to 12.0 range when eggs are fully mature.

Flexible Testing: Unlike LH, which has a short-lived surge, progesterone continues to rise gradually. This allows for testing every two to three days in most cases. Progesterone timing proves valuable for various breeding scenarios, from fresh chilled and frozen breeding to infertility evaluations and natural breeding with limited stud access.

The Ovulation Timing Process

To determine the ideal breeding time, we typically start progesterone monitoring on Day 5 of your dog’s heat cycle. Subsequent blood tests are performed every other day until the LH surge is detected, revealing the optimal moment for breeding.

The Importance of Proper Blood Sample Collection

Hemolysis, the breakdown of erythrocytes (red blood cells), is a critical factor when drawing blood for progesterone testing. Hemolyzed samples can alter progesterone results, leading to inaccurate timing. To ensure the best results, we highly recommend having all progesterone samples collected at our office. Our in-house testing provides accurate and timely results, giving you the confidence to breed at the correct moment.

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