Why is my senior cat losing weight?

Weight loss in a senior cat is almost always a medical issue. Common causes include hyperthyroidism (affects ~10% of cats over 10, causes weight loss despite good appetite), chronic kidney disease (very common over 12), diabetes, and dental disease causing pain while eating. See your vet if your cat loses more than 0.5 kg over 1-2 months.

How does obesity affect a cat's lifespan?

Obesity (more than 20% over ideal weight) can shorten a cat's lifespan by 2-3 years. It significantly increases risks for type 2 diabetes, fatty liver disease, osteoarthritis, lower urinary tract disease, and respiratory problems.

When should I be concerned about my cat's weight?

Weigh your cat monthly. Schedule a vet visit if they lose more than 0.5 kg over 1-2 months, or if you can visibly see their ribs. In senior cats (11+ years), any unexplained weight change — up or down — warrants a vet exam.

Cats

Cat Aging and Weight: What the Scale Tells You

Q: What is a healthy weight for a cat?

Most domestic cats should weigh between 3.6-5 kg (8-11 lbs). Large breeds like Maine Coons can healthily reach 6-9 kg. Body condition score (BCS) on a 1-9 scale is more meaningful than weight alone — a score of 4-5 is ideal.

Weight changes in cats are often the earliest visible sign of an age-related health condition.

Ideal Weight Ranges by Age

Most domestic cats should weigh 3.6-5 kg (8-11 lbs). Large breeds like Maine Coons can healthily reach 6-9 kg. Body condition score (BCS) on a 1-9 scale is more meaningful than weight alone; a score of 4-5 is ideal.

Life Stage	Age	Weight Trend	Key Risk
Kitten	0-1 yr	Rapid gain	Underweight
Young Adult	1-6 yrs	Stable	Obesity (post-neuter)
Mature Adult	7-10 yrs	May gain	Obesity; early organ disease
Senior	11-14 yrs	Slight loss	Hyperthyroid weight loss
Geriatric	15+ yrs	Declining	Muscle loss, CKD

Obesity and Accelerated Aging

Obesity — more than 20% over ideal body weight — significantly increases the risk of:

Type 2 diabetes mellitus
Hepatic lipidosis (fatty liver)
Osteoarthritis and joint pain
Lower urinary tract disease

Reduced lifespan (2-3 years shorter)
Respiratory problems
Reduced immune function
Increased surgical risk

Weight Loss in Senior Cats: Never Ignore It

Unexplained weight loss is one of the most important signs your cat is aging and needs medical attention. Common causes include:

Hyperthyroidism: Weight loss despite good appetite. Affects ~10% of cats over 10.

Chronic Kidney Disease: Nausea, reduced appetite, muscle wasting. Very common over 12.

Diabetes: Weight loss with increased thirst and urination.

Dental Disease: Oral pain often causes cats to eat less. Good pet dental health habits can prevent this common but overlooked cause of weight loss.

Monitor at Home

Weigh your cat monthly. A consistent loss of more than 0.5 kg over 1-2 months warrants a vet visit. Also do a rib check: you should feel ribs easily without pressing hard, but not see them visibly. For complete guidance on supporting your aging cat, our senior cat care guide covers nutrition, vet schedules, and home adjustments.

Cat Age Calculator Signs Your Cat Is Aging