A cat’s milk typically comes in about two days before she gives birth. You may notice her mammary glands swelling and even see small amounts of cream-colored secretion at the nipples as delivery approaches. The first milk she produces is colostrum, a nutrient-dense fluid packed with antibodies, which transitions to regular milk within about three days after the kittens arrive.
Mammary Changes During Pregnancy
A cat’s body starts preparing for nursing well before the kittens are born. Her mammary glands gradually increase in size throughout pregnancy, but the most noticeable changes happen in the final week. Around two days before labor, the glands begin actively producing colostrum. At this point, you might spot thick, cream-colored secretions at the nipples. Sometimes a cat won’t visibly leak, and instead the secretion dries into small whitish scabs on the nipple surface. Both are normal.
If you’re monitoring a pregnant cat and notice swollen mammary glands with dried or leaking secretions, that’s a strong signal that labor is close. Combined with other pre-labor behaviors like nesting, reduced appetite, or restlessness, visible milk production is one of the more reliable physical signs that kittens are on the way within 24 to 48 hours.
Colostrum vs. Mature Milk
The first milk a cat produces isn’t the same as what she’ll make a week later. Colostrum is thicker, richer, and loaded with immunoglobulins, the antibodies that give newborn kittens their initial immune protection. Kittens are born with almost no immune defense of their own, so colostrum is critical. Their intestines can absorb these large antibody molecules directly into the bloodstream, but only for a limited window.
By about three days after birth, two things happen simultaneously. The kittens’ intestines lose the ability to absorb whole antibodies (a process called “gut closure”), and the mother’s mammary glands shift from producing colostrum to producing mature milk. Mature milk is lower in antibodies but still nutritionally complete for growing kittens. This transition is why the first 24 to 72 hours of nursing are so important. Kittens that miss colostrum are significantly more vulnerable to infections.
How Milk Let-Down Works
Even once milk is available in the glands, it doesn’t flow freely on its own. Kittens need to stimulate it. When they knead and suckle at the nipples, pressure-sensitive receptors send signals up through the spinal cord to the brain. The brain responds by releasing oxytocin from the pituitary gland into the bloodstream. Oxytocin causes tiny muscle cells around the milk-producing tissue to contract, squeezing milk down into the ducts and out through the nipple.
This reflex is why you’ll see kittens kneading rhythmically with their paws while nursing. They’re not just being cute. That pressure is a necessary part of triggering milk release. The suckling also creates a feedback loop: the more the kittens nurse, the more oxytocin is released, and the more milk the mother produces. Prolactin, another hormone, works alongside oxytocin to sustain ongoing milk production throughout the weeks of nursing.
When Milk Doesn’t Come In
True agalactia, where a cat produces no milk at all, is uncommon. When it does happen, it’s usually a sign of an underlying problem rather than a standalone condition. Dehydration, poor nutrition, severe stress, pain from a difficult delivery, or infections like metritis (uterine inflammation) can all suppress milk production. Eclampsia, a dangerous drop in blood calcium, is another possible cause. In most of these cases, treating the root problem restores milk flow.
A more subtle version of the problem is inadequate milk supply. The mother produces some milk, but not enough to support the litter. If you notice kittens crying frequently, constantly trying to nurse, or not gaining weight in the first few days, the mother may not be producing enough. Healthy kittens roughly double their birth weight within the first one to two weeks. Falling short of that can indicate a supply issue.
Signs of Mastitis
Sometimes the milk comes in fine, but an infection in one or more mammary glands disrupts nursing. Mastitis can develop at any point during lactation. In early or mild cases, the only clue might be that kittens aren’t gaining weight as expected. On closer inspection, the affected gland may look slightly swollen or feel warmer than the others.
As the infection progresses, signs become more obvious. The gland turns red or purple, feels hard and painful to the touch, and the cat may flinch or refuse to let kittens nurse on that side. Milk from the infected gland can look cloudy, thickened, or contain visible blood or pus. In severe cases, the skin over the gland may ulcerate and develop open sores. Mastitis requires prompt treatment, as the infection can spread and the affected milk can make kittens sick.
Supporting a Nursing Cat
A lactating cat’s caloric needs can be two to three times higher than normal, especially with a large litter. Feeding a high-quality kitten food (which is more calorie-dense than adult formulas) during late pregnancy and throughout nursing helps ensure she has the energy and nutrients to maintain her milk supply. Fresh water should always be available, since dehydration is one of the simplest and most preventable causes of reduced milk production.
Keep her nesting area quiet, warm, and low-stress. Stress hormones can interfere with oxytocin release and disrupt the let-down reflex. If the mother seems reluctant to nurse or the kittens aren’t latching well in the first few hours, gently placing kittens at the nipples can help get the cycle started. Once that first round of suckling triggers oxytocin release, most cats settle into nursing naturally.