Why Is My Dog 's Vitamin D3 Level Abnormal ?
Why Is My Cat 's Vitamin D3 Level Abnormal ?
To see what normal blood and urine values are for your pet, go here
For an explanation of causes of most abnormal blood and urine tests go here
To see how tests are often grouped, go here
Ron Hines DVM PhD
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Your Pet's Blood Vitamin D 3 Levels
Cholecalciferol, Calcitriol, 25-hydroxy vitamin D test, 25(OH)D3
Vitamin D, in its D3 form, is one of the essential fat soluble vitamins that your dog or cat obtains from its diet.
You and I can do with dietary sources of vitamin D2 or simply produce vitamin D from cholesterol-like compounds in our skin (7-dehydrocholesterol) when we are exposed to sunlight. But most carnivores, including dogs and cats have lost that ability. Your pet would normally obtain adequate D3 from liver, egg and meat ingredients in its diet. But pet food manufacturers fortify their foods with extra vitamin D3 - just to be sure.
Adequate vitamin D3 is essential to maintain proper levels of calcium and phosphorus in your pet’s blood. That in turn, keeps your pet’s bones properly mineralized and strong. Proper blood calcium levels are dependent on vitamin D3 stores as well as your pet’s parathyroid gland. That circulating calcium is essential for normal nerve function, muscle contraction and many other vital body processes.
How much vitamin D3 your pet actually requires is very dependent on the balance between calcium and phosphorus in its diet. Things function best when there is approximately 1.2 parts calcium to 1 part phosphorus in the diet of your dog or cat. Growing puppies and kittens require more vitamin D3 than adults.
When a puppy or kitten does not receive enough vitamin D3 in its diet, the result can be twisted, bowed bones (rickets). When an adult pet does not receive enough vitamin D3, the result will be weak bones that are subject to fracture (osteomalacia, osteoporosis).
Too much vitamin D in your pet's diet is just as bad as too little. When
a pet receives too much vitamin D in its diet (hypervitaminosis
D), tissues throughout its body are injured as calcium deposits in the
wrong places (metastatic calcification).
Poorly thought out diets are the most likely cause. Well-meaning pet owners might easily conclude that their pets will do just fine on the foods that they themselves do well on. That is particularly true if the owners themselves limit their consumption of meat.
To compound that potential problem, the amount of vitamin D3 in lean red meat is quite low. Liver, egg yolks and fish oils are a much better source. Red meat has a calcium to phosphorus ratio in reverse to what dogs and cats need to consume. That unhealthy, reversed ratio makes the effects of insufficient vitamin D3 even worse.
Vitamin D3 is not abundant in grain, vegetables, nuts or fruit. And your dog or cat can't simply cook some up with a walk in the sunshine like you and I can.
Reasons Your Pet’s Vitamin D3 Levels Could Be Too High (Hypervitaminosis D) :
Accidental consumption of certain rat or mouse poisons is the most common cause of excessively high vitamin D blood levels. That occurs more commonly in dogs than in cats.
The next most common cause is giving your pet too much vitamin supplement or fish oils containing vitamin D (like cod liver oil).
The next most common cause is probably feed manufacturing errors when too much vitamin premix is added to a batch of dog or cat food or to a powdered vitamin supplement.
Certain toxic plants also contain vitamin D. Pets that accidentally eat them can also end up with vitamin D toxicity as can those that accidentally eat a certain psoriasis medication (Dovonex, Calcipotriol).
High blood vitamin D levels also occasionally occur in certain cancers (lymphomas) and chronic inflammations (granulomatous diseases) that stimulate macrophage cells ( eg histoplasmosis, coccidiodomycosis, blastomycosis, etc.).
Complementary Tests :
Finding normal blood calcium levels are not a guarantee that dangerous metastatic calcification will not occur as a result of too much vitamin D.