You cannot use a human pregnancy test on a dog. Human tests detect a hormone called hCG, which is produced only by the human placenta. Dogs don’t produce hCG at all. Instead, pregnant dogs produce a hormone called relaxin, and that’s what canine pregnancy tests are designed to detect. The good news is that there are reliable ways to confirm a dog’s pregnancy, ranging from blood-based relaxin tests to veterinary ultrasound, each with its own ideal timing window.
Why Human Pregnancy Tests Don’t Work on Dogs
Human pregnancy test strips rely on antibodies that bind specifically to hCG in urine. Since dogs never produce this hormone, the test will always read negative regardless of whether the dog is pregnant. On top of that, dog urine has a different pH and chemical makeup than human urine, so the test strip isn’t calibrated to function with it in the first place. No matter how many strips you use, you won’t get a meaningful result.
The Relaxin Blood Test
The canine equivalent of a pregnancy test measures relaxin in the dog’s blood. Relaxin is a hormone released by the placenta once embryos have implanted in the uterus. It can be detected as early as day 20 of gestation, but accuracy at that point is low (around 4%). By day 29, sensitivity reaches 100%, making that the sweet spot for testing. If you test before day 25 or so and get a negative result, it doesn’t necessarily mean the dog isn’t pregnant. It may just be too early.
There are two ways to run a relaxin test. Your veterinarian can draw blood and either run the test in-clinic or send it to a lab. This is the simplest option for most pet owners. Alternatively, at-home relaxin test kits are available online for around $12 per test. These kits give results in about 5 to 10 minutes and don’t require an expensive analyzer, but they do require a small blood draw (less than 1 mL) and a centrifuge to separate the serum from the blood cells. If you’re a breeder with the equipment and experience, these kits can be practical. For the average dog owner, the blood draw and centrifuge requirement make a vet visit the easier path.
Ultrasound: The Most Common Method
Veterinary ultrasound is the most widely used tool for confirming dog pregnancies and checking fetal health. A fetal heartbeat can be detected as early as 21 to 22 days after ovulation, though the image is clearer and more reliable a bit later. Most veterinarians prefer to scan around 30 to 32 days after the last known breeding for three practical reasons: the fluid-filled sacs around each embryo are large enough to spot easily, the heartbeat is visible without specialized Doppler equipment, and the embryos are still small enough to count individually.
Later in pregnancy (beyond about 50 days), the puppies are so large that the uterine horns overlap each other on the screen, making an accurate head count difficult. So if you want to know how many puppies to expect, the 30-to-32-day window is ideal for ultrasound.
Preparation is minimal. Your dog doesn’t need to fast before a pregnancy ultrasound. Keeping a normal feeding schedule is fine. A moderately full bladder helps the vet get a clearer image, so letting your dog urinate about an hour before the appointment is a useful tip. The vet will shave a small patch of fur on your dog’s belly, apply gel, and move the probe across the abdomen. The process is painless and typically takes 10 to 20 minutes.
Abdominal Palpation
An experienced veterinarian can sometimes feel small, bead-like swellings along the uterine horns between days 21 and 30 after breeding. These swellings double in size roughly every week, but by days 35 to 38 they merge together and become impossible to distinguish from one another. That gives palpation a narrow and unforgiving window. It’s also less reliable than ultrasound or relaxin testing. The vet can’t determine fetal viability through touch alone, and getting an accurate count is difficult even with experience. Most vets use palpation as a quick preliminary check rather than a definitive diagnosis.
X-Rays for Counting Puppies
Radiographs (X-rays) become useful late in pregnancy, once the fetal skeletons have calcified enough to show up on film. This typically happens around 44 to 47 days after ovulation, or roughly 42 to 54 days after mating. Clear, unambiguous images for counting puppies are available about 17 to 20 days before the expected due date. X-rays are the most accurate way to count how many puppies are coming, which helps your vet plan for delivery and know whether all puppies have been delivered safely.
Because of the radiation involved, X-rays are reserved for later pregnancy when the skeletal structures are developed. They aren’t used for early pregnancy detection.
Physical Signs to Watch For
Before any test confirms pregnancy, you might notice behavioral and physical changes in your dog. Nipple enlargement and a pinkish color change (sometimes called “pinking up”) can appear within the first few weeks. Some dogs experience periodic vomiting, lethargy, and fluid retention, similar to morning sickness. Mammary gland development becomes more obvious as pregnancy progresses.
One important caveat: these same signs can appear in dogs that aren’t pregnant. False pregnancy, or pseudopregnancy, is common in dogs and typically begins four to nine weeks after a heat cycle. It can cause mammary enlargement (sometimes with milk production), vomiting, lethargy, and nesting behavior that looks identical to real pregnancy. This is why physical signs alone are never a reliable indicator. A relaxin blood test or ultrasound is the only way to know for certain.
Testing Timeline at a Glance
- Days 21 to 30: Abdominal palpation possible but limited in reliability. Relaxin blood test becomes detectable around day 20 but isn’t fully accurate until day 29.
- Days 29 to 32: Relaxin blood test reaches 100% sensitivity. Ultrasound is ideal for confirming pregnancy, visualizing heartbeats, and counting fetuses.
- Days 45 and beyond: X-rays can confirm fetal count once skeletons have mineralized, typically best at 17 to 20 days before the due date.
If you suspect your dog is pregnant after a known or accidental breeding, the most practical approach is to schedule a veterinary visit around day 30. At that point, both a relaxin test and an ultrasound can give you a definitive answer, a puppy count, and confirmation that the pregnancy is progressing normally.