Why 5 is NOT the Magic Number

Here is a sample of progesterone testing from a bitch who proved not once, but twice, why a progesterone level of 5 is not always the “magic number” some breeders assume it to be. She reinforced the importance of continuing to test past a level of 5, specifically with consecutive testing within a 24-hour period to accurately confirm ovulation.

Here are her results:

Breeding #1

Breeding #2

As breeders, it can be tempting to assume that once progesterone reaches 5 ng/mL, ovulation has occurred or is guaranteed to happen immediately. However, progesterone does not always rise in a perfectly predictable pattern. Some bitches plateau, rise slowly, or fluctuate before true ovulation occurs.

This is why consecutive testing is so important. A single progesterone result only provides a snapshot in time, while repeat testing allows you to identify the trend and confirm whether progesterone is actively rising as expected. Missing that progression can result in breeding too early or too late, ultimately affecting conception rates and litter size.

In this case, if testing had stopped at 5, the timing would have been inaccurate and the breedings would have been done far too early. Continued testing provided a clearer picture of her cycle and allowed for more precise breeding management.

Progesterone testing is not just about chasing a single number, it is about understanding the progression of those numbers and using that information to optimize timing and reproductive success.