Most missed breedings do not come from misreading a progesterone result. They come from not having enough results to read. A bitch tested on day 8 of proestrus and again on day 14 has left a six-day hole in the record, and the LH surge almost certainly happened inside it.
A good progesterone testing schedule is not about testing constantly. It is about testing loosely when nothing is happening and tightly when everything is. This article covers how to build that cadence.
Before you use any number on this page
Progesterone thresholds are specific to the assay that produced them. Different analyzers report systematically different values on the same blood sample, so a threshold from one instrument is not valid on another. Read your results against the reference range published for your analyzer. What does transfer between machines is the pattern — baseline, rise, confirmation — and the day counts. See how Mini Vidas, Vcheck and Finecare readings compare and why your analyzer’s chart doesn’t match the textbook.
- Draw a baseline sample around days 5 to 7 of proestrus. A confirmed low result is what makes every later result meaningful.
- Let the result, not the calendar, decide the next interval: about every 4 days near baseline, every 2 days once estrus signs appear, daily once you pass 2 ng/mL.
- Keep testing until you see a sharp continued rise to 6 ng/mL or above. A single crossing of 2 is not Day 0.
- Critical breedings need three, four or more assays. A single reading is not advised.
If you run a Finecare Vet or Pro-DX
The laboratory-scale figures in this article come from reference-method literature. This analyzer reads on its own scale and sits systematically higher: independent testing puts the regression at Finecare = 5.87 + 1.28 × reference, so on the Finecare chart estimated ovulation falls at 8–15 ng/mL and the fertile range at 15–40 ng/mL. Time from the chart supplied with your kit lot, not from the numbers in this article. See how the common analyzers compare, and why thresholds belong to the assay that produced them →
Start earlier than feels necessary
The single most common scheduling error is starting late. Breeders often wait until the bitch is clearly flagging and standing, at which point ovulation may already be behind them. Kurt De Cramer gives the same advice from the clinical side: less experienced practitioners are specifically advised to start collecting blood earlier in the estrous cycle rather than later, because experienced clinicians are better at judging when the rise is likely to begin.
A reasonable default is to draw a baseline sample around days 5 to 7 after the first sign of proestrus bleeding. That first result is usually well under 1 ng/mL, and that is exactly the point. A confirmed baseline tells you the rise has not started yet, which converts every subsequent result into a comparison rather than an isolated number.
Two situations argue for starting even earlier:
- Bitches with a history of early ovulation. If a previous cycle surged on day 7, start on day 4 this time. Individual dogs repeat their own pattern more closely than they follow the breed average.
- Bitches with minimal or hidden discharge. Small breeds and fastidious groomers can obscure the onset of proestrus by several days, meaning your “day 5” may actually be day 9.
The escalating interval
Think of the schedule as tightening in stages, triggered by the result rather than by the calendar. The pattern looks like this across a typical cycle:
The intervals themselves come straight from De Cramer’s guidance on blood collection. The trigger values in the table are on the reference laboratory scale; on your analyzer the same triggers sit at different numbers, but the logic — loose near baseline, daily once the rise starts, stop only after confirmation — transfers to every machine.
| Situation | Next test | Why |
|---|---|---|
| Near baseline, around 1 ng/mL | In about 4 days | Progesterone can remain close to basal for 10 days or longer during proestrus and early estrus. |
| Authentic signs of estrus have appeared | Every 2 days | Move on the behaviour, not on the number. |
| Any reading above 2 ng/mL | Daily, or at minimum every 2 days | A single crossing of 2 is not Day 0 on its own. Keep testing until a sharp continued rise is confirmed. |
| Confirmed sharp rise to 6 ng/mL or above | Testing has done its job | Day 0 is confirmed retrospectively. Now count forward from it. |
Most straightforward cycles resolve in four to six tests. For critical breedings — frozen or chilled semen, compromised semen, or an atypical cycle — De Cramer recommends three, four, or if required even more assays, specifically to cover the three key events: the LH peak, ovulation, and the onset of the fertile period.
Do not let the calendar create gaps
Bitches do not schedule the LH surge around clinic hours. If a bitch reads 1.8 ng/mL on a Friday afternoon and your clinic is closed until Monday, you have a problem that no amount of interpretation will fix.
Plan the weekend before you reach it. A Thursday result above 1 ng/mL is the moment to confirm Saturday availability, not Friday evening.
This is one of the strongest practical arguments for in-house or in-clinic testing. As De Cramer notes, progesterone assays have been available from commercial laboratories for years, but turnaround time impedes their usefulness in cases where an immediate clinical decision is needed — which is precisely why point-of-care assays exist. A highly accurate result that arrives 36 hours later can be worth less than a slightly different scale you can read this morning and again tomorrow. Systems such as the PETlife Pro-DX return a quantitative canine progesterone (cProg) result from 75 µL of whole blood, serum or plasma in about 15 minutes, which is what makes a daily interval realistic rather than aspirational.
How frozen semen changes the plan
Everything above assumes a natural or fresh breeding, where sperm longevity absorbs some timing error. Frozen semen removes that cushion almost entirely: thawed sperm survive in the female genital tract for a period probably not exceeding 12 hours.
Frozen semen protocol adjustments
- Move to daily testing once progesterone passes 1 ng/mL, rather than waiting for 2
- Aim to identify Day 0 within a 12 to 24 hour window, not a 48 hour one
- Consider adding direct LH testing, which requires daily sampling but pins Day 0 precisely
- Book the insemination team provisionally as soon as the rise starts, targeting Days 6 and 7 after the LH surge, one day apart — the timing established by Steckler, Nöthling and Harper in a multi-sire frozen-semen insemination trial
The economics support this. Additional progesterone tests are inexpensive compared with the cost of a frozen semen shipment, a surgical or transcervical insemination, and a lost breeding season that may not come around again for six months.
Watch the shape of the curve, not just the threshold
Two results are a line. Four results are a curve, and the curve carries information the individual points do not. A bitch climbing from 0.8 to 2.4 to 9.0 ng/mL over four days is behaving very differently from one moving 0.9 to 1.6 to 2.8 over the same period, even though both crossed the same threshold.
A slow or stalling rise is worth raising with your veterinarian. It may be nothing more than individual variation, but it can also be a false rise that will fall back below 2 before the real one arrives. Either way it is a reason to keep testing rather than to assume the timeline from here is standard.
Cycles that need a different approach
All three are made harder by how elastic the canine cycle is. Drawing on Johnston, Root Kustritz and Olson, proestrus averages 9 days but ranges from 1 to 27 days in extreme cases; Beijerink puts estrus at an average of 9 days with a range of 3 to 21. Nothing about the calendar is reliable enough to substitute for testing.
A working progesterone testing schedule
- Record the first day of proestrus discharge as accurately as you can
- Draw a baseline sample around day 5 to 7
- Test about every 4 days while results stay near baseline
- Tighten to every 2 days once authentic estrus signs appear
- Move to daily testing the moment any result exceeds 2 ng/mL
- Do not lock in Day 0 until a sharp continued rise to 6 ng/mL or above is confirmed
- Keep every result, including the boring baseline ones, for next cycle’s planning
That last step matters more than it looks. The baseline results are what let you start at the right point next time, and over two or three cycles they turn a generic schedule into one tuned to the individual dog. The free Pup Planner app keeps those results plotted against the dog rather than scattered across notebooks and text messages.
Frequently asked questions
When should the first progesterone test of the cycle be taken?
Around days 5 to 7 after the first sign of proestrus bleeding for most bitches. Start earlier if she has surged early in a previous cycle, or if her discharge is easy to miss. Starting too early costs one inexpensive test; starting too late can cost the season.
Is testing every other day enough?
Every 2 days is the right interval once estrus signs appear, but once any result exceeds 2 ng/mL you should move to daily. A 48 hour gap there can move your Day 0 estimate by a full day, which is most of the available margin with frozen semen.
Can I stop testing once progesterone is clearly rising?
Once you have confirmed a sharp continued rise to 6 ng/mL or above, yes. Day 0 is established and the calendar takes over. Stopping before that confirmation is what leaves you exposed to anchoring on a false rise.
Sources
De Cramer K. Simplifying the Canine Reproductive Cycle Using the Concentration of Progesterone. IDEXX Laboratories, CLD-12211-00. Sections on the number of assays required and the interval between blood collections.
Steckler D, Nöthling JO, Harper C. Prediction of the optimal time for insemination using frozen-thawed semen in a multi-sire insemination trial in bitches. Anim Reprod Sci. 2013;142(3–4):191–197.
Johnston SD, Root Kustritz MV, Olson PNS. Canine and Feline Theriogenology. WB Saunders; 2001.
Beijerink N. Endocrinology of physiological and progestin-induced canine anoestrus [dissertation]. Utrecht University; 2007.
Keep reading
Threshold values in this article are drawn from published veterinary literature and are assay-dependent: absolute numbers are not interchangeable between analyzers. Always interpret results against the reference range for the instrument you are using. This article is educational and is not a substitute for veterinary advice. Testing intervals, sampling, and breeding decisions should be planned with your veterinarian or a board-certified theriogenologist.