Calcium and Bone Health in Cats: Why an All-Meat Diet Breaks Bones

Quick answer

A cat on a complete, life-stage-appropriate diet already has its calcium sorted. The bone problems in cats come from diets built out of meat.

A cat eating a complete commercial diet does not need calcium. It needs you not to add any. The real feline bone disease is the opposite problem: a cat, usually a kitten, fed meat and nothing else.

Muscle meat contains many times more phosphorus than calcium. Fed alone it forces the body to strip calcium out of the skeleton to keep blood levels normal, and within weeks a growing kitten has bones that break during ordinary play. The condition is called nutritional secondary hyperparathyroidism, and it is entirely preventable.

• Do not give calcium supplements to a cat on a complete diet. More is not better and it causes its own problems.
• An all-meat diet, including chicken, mince, or raw muscle meat, is the classic cause of feline bone disease. Wild cats eat whole prey, which is a completely different thing.
• A kitten that has stopped jumping, is reluctant to move, is lame, or cries when picked up needs a vet the same day.
• Home-prepared and raw diets must be formulated by a qualified veterinary nutritionist. Internet recipes for cats are frequently deficient.
• Cod liver oil and liver-heavy diets cause vitamin A toxicity in cats, which fuses the neck and is crippling.

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Never give a cat human calcium tablets, vitamin D supplements, or cod liver oil.

Vitamin D given to a cat in a human dose causes blood calcium to rise, which damages the kidneys and deposits calcium into soft tissues. It is the same mechanism as the rat poison that contains cholecalciferol. Cod liver oil and other liver-heavy feeding cause the opposite excess, vitamin A toxicity, which in cats produces bony outgrowths that fuse the neck vertebrae and the front limb joints. Affected cats cannot groom, cannot turn their heads and are in constant pain. Both of these are owner-caused, both are described in cats specifically, and neither is reversible once the changes are established.
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Decide in 60 seconds

Why meat alone breaks a cat

A cat's skeleton is a calcium store as well as a structure. The body will always protect the blood calcium level first, because calcium is required for nerves, muscle and the heartbeat, and it will spend the skeleton to do it.

Feed a diet that is high in phosphorus and low in calcium, and blood calcium starts to drop. The parathyroid glands respond by releasing parathyroid hormone, which pulls calcium out of bone and puts it back into the blood.

That system works. Blood calcium stays close to normal, the cat carries on eating and playing, and there is no obvious sign anything is wrong. Meanwhile the bones thin out.

In an adult cat this takes a long time. In a growing kitten it can take weeks, because the skeleton is being built at the same time as it is being raided, and the result is bone that looks almost transparent on a radiograph.

The first sign is usually mechanical. A kitten jumps down from a chair and fractures a leg. Or it goes quiet, stops jumping, resents being picked up, and walks with short careful steps because the bones themselves hurt.

Two consequences catch owners out. A pelvis that has bent inward narrows the birth canal and the passage for faeces, causing constipation that can persist for life. And a vertebra that collapses can compress the spinal cord, producing weak or paralysed hind legs.

Why "what cats eat in the wild" is a bad argument

A wild cat eats a mouse. It eats the bones, the organs, the skin and whatever is in the gut, and the whole animal is a balanced meal built by evolution.

A bowl of chicken breast is not a mouse. It is one tissue out of an animal, selected because humans like it, and it lacks the bone that carries the calcium, the organs that carry the vitamins, and the balance that makes the rest of it safe.

The same argument gets used for liver. Liver is a genuine part of a natural diet, in small amounts, and liver as a large part of the diet causes vitamin A toxicity, which in cats produces new bone growth around the neck and shoulder joints. Those cats cannot turn their heads to groom, cannot look up, and are in chronic pain.

Balance is the whole point. Neither deficiency nor excess is fixed by adding more of something.

What healthy bone and movement look like

A cat reaching full stretch up a post is loading its spine, shoulders and hind limbs through their whole range. A cat that has stopped doing this has usually stopped because it hurts.

A kitten that jumps without thinking.

Confident jumping up and down from furniture, landing softly, and climbing. A kitten that hesitates before a jump it used to make, or that takes the long way round, is telling you something.

Full-body stretching.

Reaching up a scratching post, arching, and stretching out on waking. Cats do this constantly when they are comfortable.

Straight limbs and a normal gait.

No bowing, no swelling around a joint, no short shuffling steps, no dragging.

No reaction to being picked up.

A kitten that cries, tenses, or turns to bite when lifted around the body is often in bone or joint pain, not being difficult.

Steady growth.

A kitten that is gaining weight and length on schedule. Poor growth alongside reluctance to move is a strong combination.

Normal defecation.

Regular, formed stool. Persistent constipation in a young cat that has been on a meat diet is a reason to have the pelvis imaged.

Feeding for bone health, which is mostly just feeding properly

Weighing the ration matters for weight control. For bone health, the thing that matters is that the food is complete for the cat's life stage.

Use a food labelled complete for the life stage.

Look for a statement on the packaging that the food is complete and balanced, and for which life stage. Growth and reproduction is not the same as adult maintenance, and a growing kitten needs a growth formulation.

Complementary foods, which include most pouches sold as treats, toppers, or "in jelly" side products, are not designed to be a whole diet. Read the label rather than the marketing.

Do not add anything to a complete diet.

No calcium powder, no bone meal, no eggshell, no vitamin drops. A complete food is a formulation, and adding one mineral changes the ratios of several others. Excess calcium during growth also interferes with the absorption of other minerals, including zinc.

If you feed home-prepared or raw, get it formulated.

Not adjusted, not checked against a website. Formulated by someone with a qualification in veterinary nutrition, for your cat, and then followed exactly. Surveys of publicly available home recipes for cats repeatedly find nutrient shortfalls, and the person following the recipe has no way to detect them until the cat is ill.

Do not feed bones as a calcium source.

Cooked bones splinter and cause obstructions and perforations. Raw bones carry their own risks of fractured teeth, obstruction and bacterial contamination. There are safer ways to get calcium into a cat, and the simplest is a food that already has it.

Milk is not a calcium plan.

Most adult cats lose the ability to digest lactose, so cow's milk mainly produces diarrhoea. Special cat milks avoid the diarrhoea and are still just extra calories.

Kittens.

Feed a growth diet until your vet advises switching, which is usually around the end of the first year, and later in large slow-maturing breeds. Free access to a complete kitten food is more appropriate for a growing kitten than restricted meals.

Older cats.

The question in an older cat is usually phosphorus rather than calcium. In chronic kidney disease, controlling dietary phosphorus is one of the interventions that most reliably slows progression, and that is achieved with a prescription renal diet and sometimes a phosphate binder. Adding calcium on your own initiative works against the whole plan.

Pregnant and nursing cats.

Demand rises steeply during lactation. The answer is a growth or reproduction formulation fed generously, not a calcium supplement. Supplementing calcium during pregnancy is specifically discouraged, because it can suppress the hormonal machinery that mobilises calcium when it is really needed.

What the vet will do if bone disease is suspected

Expect a careful examination of gait, limbs, spine and pain response, and questions about exactly what the cat has been eating and for how long.

Radiographs are the key test. Bone that has lost mineral looks abnormally faint, the cortices look thin, and folding fractures or collapsed vertebrae may be visible.

Blood tests assess calcium, phosphorus and kidney function. Blood calcium is often close to normal, which is the point: a normal result does not exclude the disease, because the whole mechanism exists to keep that number normal.

Treatment is a correct diet plus confinement, usually for several weeks, with repeat imaging. Pain relief is prescribed by the vet, not sourced at home. Some fractures need surgical management, and some pelvic narrowing needs later treatment for constipation.

The outlook for a kitten caught early and confined properly is good. The bone remineralises. What does not reverse is a pelvis that has already deformed, which is another reason not to wait and watch.

What never to do

Never supplement calcium in a cat on a complete diet.

Never feed a kitten meat alone, in any form, for any length of time. This includes chicken, beef mince, fish, and raw muscle meat, and it includes doing it as a temporary measure while you decide on a diet.

Never give human vitamin D, calcium tablets, or cod liver oil to a cat.

Never assume a raw or ancestral diet is automatically balanced. The ones that are balanced are the ones that were formulated to be, and that is a property of the recipe rather than of the philosophy.

Never let a kitten with suspected bone disease jump, climb or play freely while you wait for an appointment. Confine it to a carrier or a small room with everything at floor level.

Never give a cat human painkillers for suspected bone pain. Paracetamol is lethal to cats and ibuprofen and aspirin are toxic.

Never feed cooked bones.

Never interpret a normal blood calcium result as proof that the diet is adequate.

When to get help

For almost every cat, bone health is a solved problem the moment the diet is complete and nothing is added to it.

Go immediately for a cat with muscle tremors, twitching or a seizure, a kitten that cannot use its hind legs, or any suspected fracture.

Go the same day for a kitten that has stopped jumping, is reluctant to walk, cries when picked up, is lame, or has a limb that looks bent or swollen, and confine it to a small space until you are seen.

Book this week if your cat or kitten has been eating meat alone or a home-prepared diet that has not been formulated, even if it looks completely well. Radiographs and blood tests are how this is found before something breaks.

Book a nutrition consultation before starting any home-prepared, raw or restricted diet, and ask specifically about formulation by someone qualified in veterinary nutrition.

Bring the exact food, including the packaging, everything else the cat eats, how long it has been fed that way, the cat's age, and any weights you have recorded. In a nutritional bone problem the diet history is the diagnosis.