Vitamin D for Cats

Vitamin D, also known as the sunshine vitamin, is an essential vitamin for cats. Their feline body requires it to work properly, and a deficiency in vitamin D can result in health problems and disease. While normally, cats get enough vitamin D in their food to stay healthy, but there are some situations which can cause an imbalance of this needed vitamin. 

What does vitamin D do for cats? Do indoor cats suffer from vitamin D deficiency? Can you give vitamin D to a cat? What happens if a cat eats a vitamin D pill? Read on to find out the answers to these questions and learn about vitamin D for cats!  

Vitamin D is crucial for maintaining optimal health in cats. It contributes to bone health by managing calcium levels in the body by controlling the movement of calcium in and out of the bones, the absorption of calcium from the intestine, and the amount of calcium excreted by the kidneys.

In addition to playing a role in bone growth and maintenance, vitamin D is also necessary for the proper functioning of muscles, nerves, and the immune system.  

The recommended allowance of cholecalciferol (vitamin D3) for adult cats is 1.75 mcg/1,000 kcal ME. For weaned kittens, it is slightly lower at 1.4 mcg/1,000 kcal ME. Kittens also have a minimum requirement of 0.70 mcg/1,000 kcal ME. For both age groups, the maximum amount is 188 mcg/1,000 kcal ME. 

The recommended amount of vitamin D content in dry cat food is at least 500 IU/kg for adult cats and at least 750 IU/kg for kittens and pregnant cats. The maximum amount for adult cats is 10,000 IU/kg. Note that these requirements refer to per kg of diet, not per kg of body weight.

Unlike humans, cats do not synthesize vitamin D in their skin in response to sun exposure, so they need to obtain it through their food. Wild cats can consume vitamin D from the prey they hunt, while pet cats get it from cat foods formulated with vitamin D. Other common food sources of vitamin D for cats include:

• Fish
• Liver
• Egg yolks
• Beef 

A good-quality commercial pet food should contain all the vitamin D your cat needs, and there is usually no need to add supplements. If you’re concerned that your cat isn’t getting enough vitamin D from their food alone, talk to your vet before adding a supplement. 

Cats can become deficient in vitamin D if they are not fed a proper diet. When vitamin D levels decrease, so do calcium and phosphorus absorption. This can lead to bone abnormalities, as well as other nutritional and metabolic issues. A vitamin D deficiency can cause rickets in kittens and osteomalacia in adult cats, and has also been linked to congestive heart failure and an increased risk of cancer. 

Signs of rickets

Rickets is often seen in kittens who are fed diets deficient in vitamin D, typically homemade ones without supplementation. The most common signs of rickets in kittens include:

• Quietness
• Reluctance to move or play
• Lameness in the hind legs
• Bowing of the legs
• Inability to control muscle movements
• Swollen joints

Signs of osteomalacia

Osteomalacia, which means “soft bones,” is similar to rickets, but develops in mature bones. Signs of osteomalacia in adult cats include:

• Failure to thrive
• A poor-quality coat
• Pica
• Spinal deformities (lordosis or kyphosis)
• Brittle bones

Treatment of vitamin D deficiency

Correcting the diet is the primary treatment for rickets in kittens. This can be achieved with a high-quality commercial cat food containing an adequate amount of vitamin D. Rickets is a treatable condition, especially if there are no broken bones or irreversible damage to the bone.

Like rickets, osteomalacia is treated with a correction of the diet. The new diet should include enough vitamin D, calcium, and phosphorus to support the bones. Cats who are being treated for osteomalacia must be confined for the first few weeks to keep them from jumping or climbing as they are susceptible to fractures. While they can be given more freedom after the third week of treatment, limiting their movement until they make a complete recovery is recommended. Cats with minor or no limb and joint deformities can fully recover from osteomalacia within months. 

Since vitamin D is a fat-soluble vitamin, excess amounts are not excreted through the urine. Extra vitamin D is stored in the liver, muscle, and fatty tissue, and too much of it can be poisonous to cats. 

Common causes of vitamin D overdose in cats include: 

• Ingesting rodenticides containing cholecalciferol
• Ingesting prescription medications or supplements containing vitamin D
• Licking psoriasis creams containing vitamin D

While rare, pet foods that have been formulated improperly, whether commercial or homemade, have also resulted in vitamin D poisoning in cats. 

Signs of vitamin D overdose usually start 12 to 36 hours after ingestion. The severity of signs depends on the amount ingested. With smaller doses, a cat may exhibit the following signs:

• Lack of appetite
• Vomiting
• Diarrhea
• Abdominal pain
• Depression
• Increased drinking and urination

A cat may experience potentially life-threatening symptoms if they ingest a higher dose of vitamin D, including:

• Rapid breathing
• Difficulty breathing
• Gastrointestinal bleeding 
• Slow heart rate
• Arrhythmia
• Kidney failure

Treatment of vitamin D overdose

The sooner a cat is treated for vitamin D poisoning, the better their chances for a full recovery. Treatment depends on the amount ingested and the time since ingestion. Treatments may include:

• Induced vomiting
• Activated charcoal 
• Intravenous fluids
• Steroids
• Antacids
• Anti-nausea medications
• Medications to prevent absorption of vitamin D
• Medications to decrease calcium and phosphorus levels

Contact your vet immediately if you think your cat has overdosed on vitamin D. 

Cats who get enough vitamin D from their diets likely won’t need vitamin D supplements. In fact, too much vitamin D can do more harm than good and lead to toxicity. Cats who have been diagnosed with a vitamin D deficiency, rickets, or osteomalacia may benefit from taking vitamin D supplements, which come in the form of chewable tablets and liquid drops. Calcitriol, the active form of vitamin D, is prescribed to cats with chronic kidney disease. 

Vitamin D is toxic to cats in high doses, so always consult your vet before adding a supplement. If your cat isn’t getting sufficient vitamin D from their food, your vet may recommend a multivitamin supplement to help provide nutrients in appropriate levels. 

Vitamin D plays many important roles in the body, including maintaining bone health. Too little vitamin D in cats can lead to rickets and osteomalacia, while too much can cause poisoning. Vitamin D for cats is obtained through food, and supplements are not necessary for felines who eat a complete and balanced diet.