Progesterone testing for dog breeding: timing ovulation right
Getting a litter starts with one question: when is she actually fertile? In dogs, you cannot answer that by counting days or watching behaviour alone — every bitch is different, and the fertile window is short. Serial progesterone testing is the tool that turns guesswork into a date.
Why progesterone, not the calendar
A bitch is only fertile for a few days inside a heat that can last three weeks. Standing heat and a swollen vulva tell you she is in season, but not whether she has ovulated. Progesterone rises in a predictable curve around ovulation, so measuring it every couple of days lets you pinpoint the moment eggs are released — and eggs need ~48 hours to mature before they can be fertilised.
Reading the numbers
Values vary slightly between labs and machines, but the curve is consistent. As a working guide (ng/mL):
| Progesterone (ng/mL) | What it usually means |
|---|---|
| < 2.0 | Pre-ovulation — keep testing every 2–3 days |
| 2.0 – 3.0 | LH surge approaching; ovulation near |
| ~5.0 | Ovulation is occurring |
| 8.0 – 20.0 | Eggs maturing — the fertile window opens |
| 20.0+ | Optimal natural mating / fresh AI window |
The headline: ovulation happens at roughly 5 ng/mL, and the best conception rates come from breeding two days after that, when the eggs have matured.
Building a testing schedule
- Baseline early. Start testing around day 5–7 of the season, before you expect anything to happen.
- Test every 2–3 days while values stay under 2.5.
- Tighten to daily as you approach the 2–3 range so you do not miss the surge.
- Confirm ovulation at ~5, then plan the mating for 2 days later.
It also predicts whelping
Because the rise is tied to ovulation, the ovulation date gives you a far more accurate due date than the mating date: puppies arrive about 63 days from ovulation, give or take a day. That is why breeders who test rarely get caught out by an early or "late" whelp.
Bringing it together
Progesterone testing takes the drama out of breeding. Pair it with good record-keeping — and if you are new to the paperwork side, our guide on how to read a pedigree certificate is a good next read. Track every reading, watch the curve, and breed to the biology rather than the calendar.
Always interpret results with your reproductive vet — machine type, handling and the individual bitch all shift the exact numbers.
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