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Progesterone testing in dogs and cats has long meant a trip to the vet, a vein, and a ticking clock. Yet the hormone that governs every successful dog and cat litter is on the brink of a testing revolution. New research shows saliva strips, smartphone colour readers and even wearable sensors could soon replace the needle—giving dog and cat breeders lab-grade numbers at home, every day. In this guide I explain why progesterone still matters, compare current and future methods, and show how you can start preparing now.
- TL;DR
- What is progesterone and why does it matter in breeding?
- Why is progesterone testing so important for dog breeding?
- How is progesterone testing used in cat breeding?
- What are the current limitations of progesterone testing?
- What new progesterone testing methods are on the horizon?
- How will these innovations improve breeding success?
TL;DR
- Progesterone is essential for managing breeding, pregnancy, and delivery in dogs and cats
- In dogs, it helps time ovulation, identify optimal breeding windows, prevent premature C-sections, and diagnose issues like split heats and ovarian cysts
- In cats, it confirms post-mating ovulation, tracks pregnancy success, and prevents wasted breeding attempts
- Current testing relies on blood draws via reference labs, in-house analyzers, or point-of-care devices, each with pros and cons
- Saliva-based progesterone tests are showing strong promise, offering needle-free, daily hormone tracking from home
- Smartphone apps using AI to read test strip colors could deliver fast, lab-quality results without expensive equipment
- Wearable sensors are in development to enable continuous, real-time progesterone monitoring through collars or patches
- These innovations aim to reduce stress, improve timing accuracy, cut costs, and strengthen collaboration between breeders and vets
- While blood testing remains the gold standard, at-home options are approaching fast—transforming the future of breeding management in both species.
What is progesterone and why does it matter in breeding?
A brief history of progesterone discovery
In 1934, two American scientists—Dr. George W. Corner and his graduate student Willard M. Allen—locked themselves away in the basement of the University of Rochester medical school with barrels of pregnant-hog ovaries.
Over several feverish months they pulverized, soaked, and distilled nearly 50,000 corpora lutea, chasing a hormone they suspected was the key to a sustained pregnancy.
At dawn one April morning, Allen coaxed a few shimmering crystals from the last flask—a mere 30 milligrams of a new steroid he and Corner christened “progesterone,” literally “pro-gestation hormone.” They calculated its formula (C₂₁H₃₀O₂), published the breakthrough in Science, and overnight rewrote reproductive physiology.
How progesterone transformed dog and cat reproduction
These days, no bitch is bred and no queen is sectioned without a progesterone number beside her name. That single data point often decides whether a whelping box is full or heartbreakingly empty.
Yet I can feel the ground shifting under my stethoscope.
For decades we’ve relied on overnight reference labs or bulky in-house analyzers that grumble for 30 minutes per run. Now pocket-sized immunoassay readers, cartridge-based microfluidic chips, and cloud-linked apps are rolling out, delivering lab-grade accuracy in less than fifteen minutes right at the exam table.
Soon dog and cat breeders will track a hormone curve from their own kitchen counter while I verify results remotely, turning timing from educated guesswork into exact science.
After years of “good enough,” the era of real-time reproductive endocrinology is finally on our doorstep—and I can’t wait to retire the old centrifuge.
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Why is progesterone testing so important for dog breeding?
After 20 years in reproductive veterinary practice, progesterone is still my most reliable tool; but the applications are totally different for dogs versus cats.
In dogs, progesterone is your breeding crystal ball.
Using progesterone to time ovulation and breeding
Our canine friends are on their own schedule with spontaneous ovulation during each heat cycle.
And this is where progesterone becomes your best friend in the breeding world.
The tricky part though is that different testing methods give you slightly different numbers.
| Testing Method | Ovulation Range | Notes |
| In-house analyzers | 10-12 ng/mL | Common veterinary equipment |
| Reference labs | 5-6 ng/mL | Overnight results, different calibration |
| Point-of-care devices | 4-8 ng/mL | Varies by manufacturer |
One breeder I know was getting confused because her lab was showing the ovulation around 10-12 ng/mL, while the reference lab results were hitting closer to 5-6 ng/mL.
It’s not that one is wrong – it’s just how different machines read the same sample.
The LH surge is your starting gun. Once progesterone hits that 2-3 ng/mL threshold, ovulation is typically coming in about 48 hours. At that point, you’re usually looking at progesterone levels climbing to 4-10 ng/mL depending on your testing method.
But here’s the kicker that catches a lot of people off guard – those eggs aren’t ready for fertilization right away.
They need about 2 days to mature in the oviduct after ovulation. So your sweet spot for breeding is really 2-5 days post-ovulation, and at the time the progesterone rate can honestly be anywhere – you want it to be higher than the ovulation value… but the rate itself does not really matter.
| Timeline | Progesterone Level | What’s Happening | Action |
| Day 0 (LH surge) | 2-3 ng/mL | Ovulation trigger | Start monitoring closely |
| Day 2 (Ovulation) | 4-10 ng/mL | Eggs released | Wait for egg maturation |
| Days 4-7 | Variable (higher) | Optimal breeding window | Breed now |
I’ve seen too many breeders rush to breed right at ovulation and wonder why conception rates are lower than expected.
Patience is everything in this game.
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Preventing premature C-sections with progesterone drops
Throughout pregnancy, progesterone levels stay nice and high.
This hormone is basically the pregnancy’s bodyguard, keeping everything stable and secure.
But here’s where it gets interesting: in that final week of gestation, the placenta and ovaries suddenly slam on the brakes with progesterone production.
When progesterone crashes below 2 ng/mL, you’ve got your green light that natural whelping is coming within 24-48 hours. And that is an important marker we pay attention to when we plan elective C-sections.
| Progesterone Level | Timeline | Recommendation |
| Above 2 ng/mL | Puppies not ready | Wait and retest |
| 2 ng/mL | 48 hours | Monitor closely |
| Below 2 ng/mL | 24-48 hours | Safe for delivery |
Indeed, puppies delivered when progesterone is still elevated often have immature lungs and underdeveloped systems. I’ve seen too many litters where we jumped the gun, and those little ones just couldn’t make it because their bodies weren’t physiologically ready.
Waiting for that progesterone drop ensures the puppies are actually ready for life outside the womb.
Most breeders I work with start checking progesterone levels around day 60-61 from ovulation (or about day 58 from breeding).
Diagnosing reproductive issues in bitches
I’ve been working with dog breeders for over two decades now, and progesterone testing has completely revolutionized how we approach reproductive problems in female dogs.
| Condition | Progesterone Pattern | What You’ll See |
| Split heats | Rise then drop to baseline | Heat signs stop suddenly |
| Ovarian cysts | Stays below ovulation values | Heat behavior but no ovulation |
| Ovarian remnant | Above 0.5 ng/mL in spayed dog | Heat signs post-spay |
| Pyometra risk | High during diestrus | Infection-prone environment |
Split heats are probably the most confusing thing I see breeders deal with. It is not uncommon that a breeder bring in her champion bloodline female who’d started showing heat signs, then everything just… stopped.
Through progesterone monitoring, we can see her P4 levels rise then drop back down to baseline: a classic split heat pattern.
Ovarian cysts (and luteal failure) is another sneaky problem that progesterone testing catches beautifully.
Some females show all the classic heat behaviors—flagging, standing, swollen vulva—but their progesterone never budges from baseline levels below 1 ng/mL (2.5 nmol/L). Without testing, you’d breed these girls repeatedly with no success, wondering what’s wrong with your stud dog or your timing.
The ovarian remnant syndrome cases are honestly some of my favorites to solve, though they’re frustrating for owners. When a “spayed” female starts showing heat signs months or years after surgery, progesterone testing combined with Anti-Müllerian Hormone (AMH) testing gives us definitive answers. A properly spayed dog should have progesterone levels consistently below 0.5 ng/mL (1.3 nmol/L)—anything higher tells us there’s still functional ovarian tissue hiding somewhere.
Even for pyometra management, knowing the progesterone level helps guide treatment decisions. High P4 during diestrus creates the perfect storm for uterine infections, so understanding where a sick female is in her cycle can influence whether we use medical management or head straight to emergency surgery.
How is progesterone testing used in cat breeding?
In cats, progesterone tells a different story.
Confirming ovulation after mating
Cats are induced ovulators, which means they only release eggs when something triggers them to do so – usually mating or a hormone injection.
| Cat Reproductive Stage | Progesterone Level | What’s Happening |
| In heat (pre-mating) | Less than 1 ng/mL | Ready to mate |
| 1-3 days post-mating | Still low | Corpora lutea developing |
| 5-7 days post-mating | Above 5 ng/mL | Ovulation confirmed |
| 2 weeks post-ovulation | 15-30 ng/mL | Pregnancy established |
When a queen is in heat and acting all lovey-dovey, rolling around and calling for a mate, her progesterone levels are actually sitting pretty low at less than 1 ng/mL. She’ll stay that way until something physically triggers ovulation.
The trigger is key here. The physical act of mating – or sometimes mechanical stimulation or an injection like hCG or GnRH – causes that crucial LH surge. Then, like clockwork, ovulation typically happens about 24-36 hours later (that’s roughly 1-1.5 days).
Here’s where progesterone testing actually becomes useful in cats:
- Confirming ovulation occurred – Test about a week after breeding
- Tracking pregnancy success – P4 levels climb if ovulation was successful
- Determining if a mating was adequate – Low P4 means try again soon
When I test a queen about 5-7 days post-mating, I’m looking for progesterone levels above 5 ng/mL. That tells me ovulation actually happened and we’ve got luteal tissue producing hormones. If everything went according to plan, those levels will keep climbing to around 15-30 ng/mL by two weeks.
Avoiding failed breeding attempts in queens
The real value comes when progesterone stays at baseline levels. This tells you immediately that the mating attempt was inadequate and didn’t trigger the necessary hormonal cascade.
Instead of waiting 65+ days for kittens that will never come, you know within a week that you need to try again.
| Scenario | Progesterone at 7 Days | Next Steps |
| Successful mating | Above 5 ng/mL | Continue monitoring pregnancy |
| Failed mating | Below 2 ng/mL | Re-breed in 2-3 weeks |
| Uncertain result | 2-5 ng/mL | Retest in 3-5 days |
Queens typically return to heat within 2-3 weeks after a failed ovulation attempt. This means you can re-breed much sooner rather than losing an entire breeding season to uncertainty.
Progesterone testing in queens isn’t about timing the perfect breeding – it’s about confirming that breeding actually worked. And that is important because missed breedings is the number one cause of infertility in this species.
This simple test can save you months of waiting and help you manage your breeding program much more efficiently. Trust me, the peace of mind alone is worth it.
What are the current limitations of progesterone testing?
Here’s the reality: progesterone testing works brilliantly, but it still requires drawing blood every single time.
| Current Method | Pros | Cons |
| Reference labs | High accuracy, detailed reports | 24-48 hour wait, expensive |
| In-house analyzers | Same-day results, convenient | High equipment cost, maintenance |
| Point-of-care devices | Fast results, portable | Variable accuracy, still needs blood |
Today, blood draws and expensive analyzers are still the gold standard for progesterone testing. But studies being done in humans are exploring alternatives, and some of these innovations might eventually make their way to veterinary medicine.
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What new progesterone testing methods are on the horizon?
Will saliva tests replace blood tests?
Here’s something that gets me really excited as a vet who’s spent countless hours trying to hit tiny veins on anxious breeding dogs and cats.
Current trials are showing perfect correlation between saliva and blood progesterone levels in both dogs and cats – the only difference is that saliva concentrations are much lower. So imagine being able to test daily with simple “progesterone sticks” without any of the stress or technical challenges we face now.
The science behind this is fascinating, and I’ve been following the research closely.
In humans, home ovulation tests typically use urine to detect LH rather than progesterone, because progesterone shows up in urine as metabolites that are harder to measure quickly.
But with dogs, researchers have been experimenting with saliva-based hormone tests that could change everything for us breeders and vets.
Here’s what this could mean for our daily practice:
🐶 Dogs: Check progesterone levels every single morning during heat cycles without any needle sticks
🐱 Cats: Confirm ovulation about a week after breeding with absolutely zero drama or restraint issues
Daily monitoring becomes actually feasible instead of the every-other-day approach we’re stuck with now
The bottom line? We may see a prototype “saliva progesterone stick” in the future, and honestly, it would be a complete game-changer if it proves accurate. Daily monitoring without needle sticks would revolutionize how we approach breeding management, making it more humane and way less stressful for everyone involved.
Timeline: 2-3 years.
How mobile apps could read hormone levels with AI
Smartphone-based hormone readers are already making waves in human fertility testing, and the technology is surprisingly close to what we need for our four-legged patients. I’ve been following a few companies that are beta-testing apps with cattle breeders – basically using your phone’s camera to read test strip colors with laboratory-level precision.
| Technology | How It Works | Advantages | Challenges |
| AI Color Analysis | Phone camera + app | No expensive equipment | Lighting consistency |
| Test Strip Reading | Photography + algorithm | Quantitative results | Camera quality variance |
| Cloud Processing | Remote analysis | Continuous improvement | Internet dependency |
Here’s how it works: instead of investing thousands in expensive analyzers, you’d simply photograph your test strip and let AI software do the heavy lifting.
The app analyzes color intensity and gives you quantitative results right on your screen. One breeder I work with joked that her phone might soon be more accurate than some of the older equipment she’s been using for years.
For dog breeders, this could mean:
- Photographing ovulation test strips for exact timing predictions
- Getting precise progesterone readings without the guesswork
- Running tests at home instead of multiple vet visits
Cat breeders would benefit from:
- Instant post-breeding confirmation results
- More affordable frequent testing during breeding season
- Better tracking of hormone cycles in queens
The technical challenges are real though.
Lighting conditions and camera quality can definitely affect results, which is why official products would need calibration for different phone models.
The technology isn’t perfect yet – we still need to work out standardization issues and ensure consistent results across different devices. But honestly, I’m more optimistic about this development than I’ve been about any breeding technology in the past decade.
Timeline: 1-2 years.
Can wearable tech provide real-time hormone tracking?
The science behind this is actually fascinating.
Researchers have been developing biosensors that can detect hormones in bodily fluids like interstitial fluid and even sweat.
| Wearable Type | Detection Method | Current Status | Veterinary Timeline |
| Collar sensors | Interstitial fluid | Research phase | 5-7 years |
| Patch sensors | Sweat analysis | Human trials | 7-10 years |
| Implantable chips | Blood chemistry | Concept stage | 10+ years |
Back in 2021, a team at Caltech created a wearable patch sensor that could measure estrogen levels in human sweat using special DNA molecules called aptamers that literally light up when the hormone is present.
Now, I know what you’re thinking – we’re not quite there yet for our four-legged patients.
But the foundation is being laid, and it’s pretty promising.
Here’s what the future might look like:
- A collar sensor that alerts your phone when progesterone spikes or drops
- Real-time monitoring that eliminates the guesswork from timing breedings
- No more daily blood draws or stressed-out animals
The early development work is actually focusing on horses and cattle right now, which makes sense given the economic stakes in those industries.
But the applications for companion animal breeding are obvious.
For Dogs: Imagine getting a real-time alert on your phone the moment that LH surge hits, or when progesterone starts its pre-whelping drop.
For Cats: The continuous monitoring aspect would be a game-changer for breeding programs, especially with those tricky feline ovulation patterns we’re always trying to track.
We’re probably looking at 5-10 years before we see practical veterinary hormone wearables hit the market. The technology needs to get more reliable, and honestly, it needs to get cheaper too.
But when it does arrive, this could completely change how we approach breeding management. No more guesswork, no more missed ovulations, and definitely fewer stressed animals getting poked with needles every day.
Timeline: 5-10 years.
How will these innovations improve breeding success?
Better timing without travel or stress
For decades, progesterone testing has meant one thing: blood draws at the veterinary clinic. While this approach works well, it’s created challenges—scheduling conflicts during critical heat cycles, stressed animals, travel limitations for remote breeders, and cost barriers for frequent monitoring.
| Current Challenges | Future Solutions |
| Scheduling conflicts during heat cycles | Test at home anytime |
| Stressed animals from blood draws | Non-invasive saliva testing |
| Travel limitations for remote breeders | Smartphone-based analysis |
| Cost barriers for frequent monitoring | Cheaper daily testing options |
| Single-point data snapshots | Continuous monitoring capabilities |
Stronger collaboration between breeders and vets
The emerging technologies promise something exciting: more options, better data, and stronger partnerships between breeders and veterinarians. Imagine combining traditional blood work for baseline accuracy with daily home monitoring for fine-tuned timing. Picture your vet having access to continuous hormone data instead of single-point snapshots.
Using continuous data to make smarter decisions
These new tools won’t replace veterinary expertise—they’ll enhance it. Your reproductive veterinarian will have richer data to work with, and you’ll have the flexibility to monitor as often as needed without clinic visits for every test.
“Innovation distinguishes between a leader and a follower,” Steve Jobs observed. In breeding, that innovation means expanding our toolkit while strengthening the breeder-veterinarian partnership.
The days of frantic clinic runs and bruised veins are numbered. Saliva strips, AI-powered phone readers, and even wearable sensors are poised to make progesterone testing in dogs and cats faster, cheaper, and far more breeder-friendly. While blood assays remain the gold standard today, forward-thinking breeders are already mapping out how to blend rock-solid lab data with next-gen, at-home monitoring for bullet-proof timing.
DR. EMMANUEL FONTAINE 