Cat's Nipples Are Swollen? Pregnancy, Hormones or Mastitis

If your cat's nipples are swollen, pregnancy or a hormone surge may be why; a hot, painful or dark gland can mean mastitis and needs an ER now.

Go to an emergency vet now if a swollen gland is hot or painful, turns dark purple or black, has an open sore or drains pus or blood, or if your cat has a fever, is lethargic, won't eat, is vomiting, has trouble breathing, is pregnant and has any vaginal discharge (especially blood) before labor starts, is ignoring her nursing-age kittens, or has nursing-age kittens that are weak or won't nurse.

If your cat's nipples are swollen: what is normal and what is not

The Cornell Feline Health Center explains, "A cat has two 'chains' of four mammary glands and nipples running parallel on each side of its belly."

Swelling in one or more glands can come from pregnancy, false pregnancy, a hormone-driven overgrowth called mammary hyperplasia, mastitis (an inflamed gland that PetMD says is usually linked to a bacterial infection) or mammary tumors. A vet sorts these out from her history (spayed or not, possible mating, nursing or just weaned, age) and an exam; you can't reliably tell them apart at home.

Two words matter here. Hot or painful are emergency words: go to an emergency vet now. Firm is different: a firm but painless gland or lump with no emergency sign needs an in-person exam soon.

If a young, unspayed cat is also yowling and rolling, see our guide on whether a cat is in heat or in pain.

Emergency signs: go to an ER now, not a video call

Go to an emergency vet now if you see any one of these:

• a gland that is hot or painful
• dark purple or black skin over a gland
• an open sore, or pus or blood draining
• fever, lethargy, not eating or vomiting
• trouble breathing
• a pregnant cat with any vaginal discharge, especially blood, before labor starts
• a mother ignoring her nursing-age kittens
• nursing-age kittens that are weak or won't nurse

VCA's overview of mastitis in cats notes that in severe mastitis, "The affected mammary gland may appear dark purple or black in color" and that "Affected cats may become lethargic, develop a fever, refuse to eat, or begin vomiting." PetMD's guide to mastitis in cats says, "In severe cases, the skin over the gland may become dark and ulcerated (having an open sore)."

For pregnant cats, PetMD says, "Vaginal discharge, especially blood, is not normal at any stage of gestation. Take your cat to an urgent veterinary visit if this occurs." This article is stricter: before labor starts, any vaginal discharge means go to an emergency vet now.

On mastitis, the Merck Veterinary Manual notes, "The mother may also neglect her kittens."

If you are unsure whether a sign is present (for example whether a gland is hot, whether she flinches because it hurts, or whether a pregnant cat's labor has started), go to an emergency vet now.

Pregnancy: the "pinking up" sign, and where labor fits

PetMD describes an early pregnancy sign: "This is where a queen's nipples become pinker and more prominent." It adds, "This occurs about 16–20 days into the pregnancy, known as 'pinking up.'"

A recently adopted or indoor-outdoor unspayed cat can be pregnant without anyone knowing. Pink, prominent, painless nipples with no emergency sign are a clear case for a video vet, who can review her history and plan an in-person confirmation. Never assume swelling is just pregnancy if any emergency sign is present.

PetMD says a veterinarian may be able to palpate (feel) fetuses about two and a half weeks into the pregnancy, and "Kitten heartbeats can be seen by ultrasound at three to four weeks into the pregnancy."

Any vaginal discharge, especially blood, in a pregnant cat before labor starts means go to an emergency vet now. Once labor has started, the emergency signs in our labor guide apply instead, and if you are unsure whether she is in labor or whether a sign is normal, go now.

False pregnancy and mammary hyperplasia: swelling driven by hormones

The Merck Veterinary Manual says false pregnancy "is uncommon in cats but occurs when they have been induced to ovulate but did not conceive." Merck adds that "the condition usually ends on its own in 1 to 3 weeks," and warns, "You should not milk out the mammary glands, because this will only stimulate production of more milk."

Mammary hyperplasia, PetMD says, is primarily limited to "young, sexually intact, cycling, or pregnant queens," and can show up as "Firm, nonpainful masses in the chest, and abdominal area." Merck says this condition "is due to the effects of progesterone and is not cancerous."

A painless firm enlargement with no emergency sign needs an in-person exam soon, because only a hands-on exam can tell it from a tumor. Tell the vet about any hormone treatment she has had.

PetMD notes that hyperplasia "may be confused with or lead to mastitis," and that the skin over enlarged glands "can become damaged, which may lead to infection." If an enlarged gland becomes hot or painful, turns dark purple or black, opens into a sore or drains pus or blood, go to an emergency vet now.

Mastitis: when a nursing or newly weaned mother has a sore gland

VCA says, "Mastitis is most frequently seen in the postpartum period (the time after a cat gives birth)," and "Many cases follow sudden weaning (when kittens stop nursing) or the death of a kitten."

PetMD lists an inflamed gland as possibly warm to the touch, red, swollen, firmer than normal or painful. VCA notes an early clue: "the nursing kittens are not gaining weight as quickly as expected."

A gland that is hot or painful, a mother ignoring her nursing-age kittens, or nursing-age kittens that are weak or won't nurse means go to an emergency vet now. If you cannot tell whether a warm gland is hot, go now.

If the gland is only red, swollen or firmer than normal, and the mother is eating, alert and caring for her kittens with no emergency sign, she needs a vet the same day (a video vet can look first), as do kittens that nurse but are not gaining weight as quickly as expected, with no emergency sign.

A lump near a nipple: why it needs an in-person exam

A Cornell veterinary oncologist, quoted by the Cornell Feline Health Center, explains that "A tumor can start as a small, firm nodule, about the size of a BB, just beneath or next to a nipple." The Merck Veterinary Manual says, "Approximately 90% of mammary tumors in cats are malignant (cancerous)." Cornell advises that "any such alarming discovery should be reported to a veterinarian without delay."

PetMD says, "A veterinary examination is needed if a spayed cat's nipples become swollen," listing causes including "a piece of an ovary being left behind during a spay, hormone exposure through medications, tumors that produce hormones, or mammary cancer."

If a lump is hot or painful, has dark purple or black skin over it, is open or draining, or your cat has a fever, is lethargic, won't eat, is vomiting or has trouble breathing, go to an emergency vet now. A painless firm lump or enlargement with no emergency sign needs an in-person exam soon, booked without delay; never watch it for months. If you are unsure, go now.

What to do tonight

Look, don't squeeze. In good light, compare both sides of her belly: which glands are swollen, their color, any nipple discharge. Gently touch near a swollen gland; if she flinches or pulls away, treat it as painful and go to an emergency vet now.

Don't squeeze or milk her glands unless a veterinarian who has examined her tells you to, and don't put human creams or medicines on her nipples. Note her appetite and energy, and whether any kittens are nursing and look full.

If any emergency sign is present, or you are unsure whether one is, go to an emergency vet now. Only if there is no emergency sign, take clear photos and a short video of her belly and of the kittens nursing.

What a RexVet online vet can do when your cat's nipples are swollen

A video visit is only for cats with no emergency sign. RexVet's veterinarians are licensed in Florida, New York and Virginia. On camera, a RexVet vet can:

• look at the size, color and symmetry of her glands and any nipple discharge
• watch while you gently touch near a gland; if she pulls away, the vet treats it as painful and sends you to an emergency vet
• take her heat, mating, pregnancy, nursing, weaning, spay and medication history, and review your photos and video
• tell you whether she needs an emergency vet now, a vet the same day, an in-person exam soon, or watching at home

The clearest video cases are an unspayed cat with pink, painless nipples and a pregnancy question; a nursing or newly weaned mother with a red gland but no emergency sign; and a new adopter who doesn't know the cat's history.

A video vet cannot feel whether a lump is firm or painful, tell a benign lump from cancer, test milk, take x-rays or an ultrasound, confirm a pregnancy, diagnose mastitis, biopsy a lump or spay. If the veterinarian decides medication is appropriate, they can prescribe where state rules allow.

If your cat has no emergency sign, you can book a RexVet video visit for $64.99, available 24/7 for pet parents in Florida, New York and Virginia.

When to be seen in person in Florida, New York or Virginia, and preventing it next time

Any sign on the emergency list means go to an emergency vet now. With no emergency sign, a painless firm lump or enlargement, a spayed cat with swollen nipples, a suspected pregnancy, or swelling that is not settling needs an in-person exam soon; a red gland in a nursing or newly weaned mother needs a vet the same day.

For prevention, PetMD says, "Spaying is the best form of prevention, since most cases of mastitis in cats are connected to lactation (nursing)." For hyperplasia, Merck notes, "Spaying prevents it from happening again." Cornell says, "Spaying before the age of six months can reduce a cat's risk of mammary cancer by as much as 91%," and suggests "routinely palpating a cat's underside in the areas of the mammary glands and nipples" on a weekly basis.

If her swelling comes with no emergency sign, you can book a video visit now; RexVet's vets are available 24/7 for pet parents in Florida, New York and Virginia, and a visit is $64.99.

Frequently Asked Questions

Why are my cat's nipples swollen if she isn't pregnant?

Swelling can come from false pregnancy, mammary hyperplasia, mastitis or a tumor, and a painless firm lump or enlargement with no emergency sign needs an in-person exam soon. Go to an emergency vet now if you see any of these, or are unsure whether one is present: a hot or painful gland; dark purple or black skin over a gland; an open sore, or pus or blood draining; fever, lethargy, not eating or vomiting; trouble breathing; any vaginal discharge, especially blood, in a pregnant cat before labor starts; a mother ignoring her nursing-age kittens; or nursing-age kittens that are weak or won't nurse.

How early can you tell a cat is pregnant from her nipples?

PetMD says "pinking up," when a queen's nipples become pinker and more prominent, occurs about 16–20 days into the pregnancy; a veterinarian confirms pregnancy in person by feel or ultrasound. Go to an emergency vet now if you see any of these: a hot or painful gland; dark purple or black skin over a gland; an open sore, or pus or blood draining; fever, lethargy, not eating or vomiting; trouble breathing; any vaginal discharge, especially blood, in a pregnant cat before labor starts; a mother ignoring her nursing-age kittens; or nursing-age kittens that are weak or won't nurse. If you are unsure whether a sign is present or whether labor has started, go to an emergency vet now.

Is mastitis in a nursing cat an emergency?

Yes, when any emergency sign is present: a hot or painful gland; dark purple or black skin over a gland; an open sore, or pus or blood draining; fever, lethargy, not eating or vomiting; trouble breathing; any vaginal discharge, especially blood, in a pregnant cat before labor starts; a mother ignoring her nursing-age kittens; or nursing-age kittens that are weak or won't nurse. In that case, or if you are unsure, go to an emergency vet now. If a gland is only red, swollen or firmer than normal, and she is eating, alert and caring for her kittens with no emergency sign, she needs a vet the same day. VCA's early clue, "the nursing kittens are not gaining weight as quickly as expected," also needs a vet the same day when no emergency sign is present.

Why does my spayed cat have swollen nipples?

PetMD says, "A veterinary examination is needed if a spayed cat's nipples become swollen," listing causes such as a piece of an ovary left behind during a spay, hormone exposure through medications, hormone-producing tumors or mammary cancer; with no emergency sign, book an in-person exam soon. Go to an emergency vet now if you see any of these, or are unsure whether one is present: a hot or painful gland; dark purple or black skin over a gland; an open sore, or pus or blood draining; fever, lethargy, not eating or vomiting; trouble breathing; any vaginal discharge, especially blood, in a pregnant cat before labor starts; a mother ignoring her nursing-age kittens; or nursing-age kittens that are weak or won't nurse.

Should I squeeze or milk my cat's swollen nipples?

Don't squeeze or milk her glands at home unless a veterinarian who has examined her tells you to; in false pregnancy, the Merck Veterinary Manual notes that milking out the glands "will only stimulate production of more milk." Go to an emergency vet now if you see any of these, or are unsure whether one is present: a hot or painful gland; dark purple or black skin over a gland; an open sore, or pus or blood draining; fever, lethargy, not eating or vomiting; trouble breathing; any vaginal discharge, especially blood, in a pregnant cat before labor starts; a mother ignoring her nursing-age kittens; or nursing-age kittens that are weak or won't nurse.