Dog health guide · Postpartum symptoms

Mastitis in Nursing Dogs: Symptoms and When to Call the Vet

A daily mammary gland check takes less than a minute and can catch mastitis early, before it progresses from mild inflammation to a serious infection.

Warning signs graphic representing when a dog symptom needs emergency veterinary care
Amy Shojai
Written by , Certified Animal Behavior Consultant (CABC) · Updated July 11, 2026 • 6 min read
⚡ Quick Answer

Mastitis is inflammation or infection of the mammary glands, and it can range from a mild, single swollen gland to a severe, hot, hard gland accompanied by fever and lethargy in the mother. A daily hands-on check of each mammary gland during the first few weeks of nursing helps catch it early. Mild cases sometimes resolve with guidance from your vet, but any gland that is hot, hard, discolored, or paired with the mother feeling unwell needs prompt veterinary attention.

How to do a daily mammary gland check

During the first few weeks of nursing, take a minute each day to gently feel each of the mother's mammary glands. Healthy glands should feel relatively soft, similar in size to one another, and not noticeably warmer than the surrounding skin. You're checking for:

Catching a change early, while it's still mild, generally makes treatment simpler and recovery faster.

Mild versus severe mastitis

Mastitis exists on a spectrum. A mild case often involves one gland that's somewhat warm, mildly swollen, and tender, while the mother otherwise continues eating, nursing, and behaving normally. A more severe or septic case involves a gland that's hard, hot, and discolored, sometimes with a bluish or purplish tinge, and the mother herself often seems unwell: fever, lethargy, reduced appetite, and reluctance to let puppies nurse from the affected side. Severe mastitis can progress to a systemic infection if untreated, which makes it genuinely dangerous rather than just uncomfortable for the mother.

When to call the vet

Any suspected mastitis is worth a call to your veterinarian, since what looks mild in the morning can become more serious quickly. Contact your vet the same day if you notice a hard, hot, or discolored gland, abnormal discharge, or if the mother is acting unwell, off her food, running a fever, or reluctant to nurse. Don't wait to see if it resolves on its own, particularly if the mother herself seems sick rather than just having one uncomfortable gland.

What treatment usually looks like

Treatment depends on severity. Mild cases may be managed with warm compresses, continued nursing or manual expression to help keep the gland from becoming further engorged, and close monitoring, sometimes without antibiotics if there's no sign of infection. More significant or infected cases typically require antibiotics, and in severe abscessed cases, your vet may need to drain the affected gland surgically. If a gland is significantly affected, your vet may recommend keeping puppies from nursing on that side temporarily, in which case you'll need a plan for supplementing those puppies' feeding, such as bottle feeding or shifting them to unaffected glands, until the gland recovers.

📚 Trusted Resources: For further reading and clinical guidance, we recommend the American Veterinary Medical Association (AVMA) and VCA Animal Hospitals.
How do I check a nursing dog for mastitis?
Gently feel each mammary gland daily during the first few weeks of nursing. Healthy glands should feel soft and roughly even in size and temperature. A gland that feels firm, hot, swollen, discolored, or noticeably more tender than the others is a sign to check further, and possibly a reason to call your veterinarian.
What is the difference between mild and severe mastitis?
Mild mastitis usually involves one gland that is warm, mildly swollen, and tender, with the mother otherwise acting normally. Severe or septic mastitis involves a hard, hot, discolored gland, often with a fever, lethargy, and reduced appetite in the mother, and can become life-threatening if untreated. Any suspected mastitis should be evaluated by a veterinarian, since it can progress quickly.
Can puppies still nurse from a gland with mastitis?
This depends on the severity and your veterinarian's guidance. In some mild cases, continued nursing or manual expression of the affected gland can help resolve mild inflammation. In more severe or infected cases, a veterinarian may recommend keeping puppies away from the affected gland, and you may need to supplement those puppies' feeding until the infection resolves.