Breeding & Reproduction
The Canine Heat Cycle and Progesterone Timing for Breeding
Updated September 6, 2026 · 8 min read · By the BreedBloom team
Most missed litters are timing problems, not fertility problems. A bitch is fertile for a short window that does not line up reliably with the day she starts to stand. Progesterone testing puts a number on it.
The four stages
Stage
Typical length
What you see
Proestrus
~9 days (3–17)
Vulvar swelling, bloody discharge, attracts males but refuses
Estrus
~9 days (3–21)
Discharge lightens, she stands and flags; ovulation occurs here
Diestrus
~60 days
Progesterone high whether pregnant or not
Anestrus
~4–5 months
Reproductive rest
Because proestrus and estrus vary so much between bitches, and between cycles in the same bitch, day-counting from the first drop of blood is a guess. The classic "breed on day 11 and 13" advice works often enough to be dangerous.
What progesterone tells you
Progesterone (ng/mL)
Event
Meaning
< 1
Baseline
Still in proestrus; retest in 2–3 days
~2–3
LH surge
Ovulation will follow in about 2 days
~5–8
Ovulation
Eggs are released but need 2–3 days to mature
> 10–15
Post-ovulation
Fertile window is open; peak fertility about 2–4 days after ovulation
Falling
End of window
Eggs are aging; late breedings produce smaller litters
Use the trend, not a single number
Labs and analysers differ. Establish the reference thresholds with your veterinarian and stay on the same machine for the whole cycle so the trend is comparable.
Timing by breeding method
•
Natural breeding or fresh semen: sperm can live 5–7 days in the bitch, so breed 2 and 4 days after ovulation, or every other day from the LH surge.
•
Fresh-chilled shipped semen: lasts 24–48 hours; inseminate 3 and 5 days after ovulation, or a single insemination on day 4.
•
Frozen semen: lives roughly 12–24 hours; must be placed (usually surgically or transcervically) 4–5 days after ovulation. Progesterone timing is not optional here.
A practical testing plan
1.
Begin testing around day 5–7 of proestrus.
2.
Retest every 2–3 days until the value rises through 2–3 ng/mL (LH surge).
3.
Then test daily or every other day to catch the ovulation rise at 5–8 ng/mL.
4.
Count ovulation as day 0. Whelping is expected 63 ± 1 days later.
Record everything
Write down each test date, value, lab, and the breeding dates and method. That data sets your due date, tells you whether a miss was timing or fertility, and becomes the baseline for her next cycle. BreedBloom stores progesterone results on the breeding record and calculates the due-date window from the ovulation date.
Frequently asked questions
What progesterone level means a dog is ovulating?
Ovulation is generally associated with progesterone around 5–8 ng/mL, about two days after the LH surge at roughly 2–3 ng/mL. Confirm thresholds with your veterinarian's laboratory.
How many days after ovulation should you breed?
For natural or fresh semen, about 2 and 4 days after ovulation. Fresh-chilled: 3–5 days after. Frozen: 4–5 days after.
How often do dogs come into heat?
Most bitches cycle every 6–8 months, though some breeds cycle once a year and small breeds can cycle more often. Intervals are often consistent for an individual.
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