How to Help an Underweight Dog Gain Weight Safely

By Tailwisp Editorial TeamUpdated October 17, 20263 min read

A thin dog worries owners, and rightly so. Being underweight can mean the dog is not getting enough food, or that something is stopping it from using what it eats. Helping it gain weight starts with finding out why.

Is your dog really underweight?

Use the body condition score chart. An underweight dog has easily visible ribs, spine and hip bones, little muscle cover and a deep tuck at the waist. Some breeds, such as Greyhounds and Whippets, are naturally lean, so compare with the breed's usual appearance and your vet's assessment.

See the vet first

Weight loss or failure to gain can be caused by:

• Intestinal parasites such as roundworms or giardia. See giardia in dogs.
• Dental disease or mouth pain. See dental disease in dogs.
• Digestive problems such as inflammatory bowel disease or pancreatic insufficiency
• Diabetes, thyroid disease or Addison's disease
• Kidney or liver disease
• Cancer
• Stress, anxiety or competition at feeding time
• Not enough food or poor-quality food

See our guide to causes of weight loss in dogs. Treating the cause is the key to lasting weight gain.

Calculate what your dog needs

Estimate the calories required for the target weight, then compare with what your dog eats. See our guide to how many calories a dog needs. Many underweight dogs are simply underfed relative to their activity.

Choose a calorie-dense food

Look for a complete and balanced food with higher energy density, good digestibility and quality protein and fat. Puppy foods or performance diets are often used, with your vet's approval. Avoid rich, fatty additions that could upset the stomach. For dogs with sensitive digestion, see diets for sensitive stomachs.

Feed smaller, more frequent meals

Three or four meals a day are easier to digest and can boost total intake. Keep meal times consistent and calm. Separate dogs at feeding if there is competition.

Make food appealing

• Warm the food slightly to enhance aroma.
• Add a spoonful of wet food or low-sodium broth, checking it contains no onion or garlic.
• Try different textures with veterinary advice.
• Use puzzle feeders sparingly, since they can frustrate thin dogs.

See our guide to picky eater dogs.

Introduce changes gradually

Increase calories by about ten to twenty percent every few days, and switch foods slowly. See how to switch dog food safely. Sudden changes or very fatty foods can cause diarrhea or even pancreatitis. See pancreatitis in dogs.

Supplements and appetite stimulants

Do not give supplements or medications to stimulate appetite without veterinary guidance. Your vet may prescribe medication if appropriate, or recommend probiotics or other support. See probiotics for dogs.

Monitor progress

1. Weigh every one to two weeks.
2. Record weight and body condition.
3. Take photos from above and the side.
4. Adjust food as needed with your vet.

Muscle as well as fat

Gentle exercise helps convert extra calories into muscle rather than just fat. Avoid intense exercise until weight improves.

When a rescue or stray dog is thin

Dogs from shelters or the street are often thin because of poor feeding, parasites or stress. Refeeding must be gradual, because a starved body can react badly to sudden large meals. Start with small portions of a digestible food several times a day and increase over days to weeks under veterinary guidance. Deworm and check for other illness early, and give the dog a quiet, predictable place to eat.

The takeaway

Find the cause first, then feed gradually and generously with the right food. Your vet is your partner.

This article is general educational information, not veterinary advice. Every dog is different. If your dog is unwell, or you are unsure about a symptom, diet change or medication, contact your veterinarian.