Calcium for dogs: when is it necessary and what is a good source?

According to the AAFCO nutrient guidelines for dogs, a dog’s diet should contain calcium, with the percentage required varying for different stages of a dog’s life. For growth and reproduction, the minimum calcium requirement is 1% per kg of diet. For adult dog maintenance it is at least 0.6% to a max of 2.5%.

Calcium is clearly an essential nutrient but that doesn’t mean you should start pumping your dog with calcium supplements. Most commercial dog food already contains the minimum requirement.

Supplementing calcium is only necessary in certain situations, which will be discussed in this article. Overdosing is not only counterproductive, it is hazardous to a dog’s health.

Some natural foods contain calcium. If these foods already form a regular part of pooch’s meals – whether in the form of toppings, treats or an ingredient in the feed – you may need to watch the amount given.

Why is calcium important for dogs?

Calcium plays a key role in developing and maintaining dogs’ skeleton, teeth, heart and hormonal functions as well as regulating the nervous system and blood coagulation. A deficiency in calcium can therefore have serious consequences.

When do I give my dog calcium supplements?

Since store-bought dog food usually has the minimum required calcium intake, additional calcium is not necessary unless your veterinarian recommends it. The following scenarios may require calcium supplementation under veterinary supervision:

  1.       Dogs on homemade diet or raw food
  2.       Nursing dogs
  3.       Dogs with calcium deficiency

1. Dogs on homemade diet or raw food

Fresh meals or raw food – whether those whipped up by yourself or by a home business – may sometimes lack calcium. This is especially so if the meal does not include bones or another ingredient as a replacement of bone.

Fish and certain vegetables may contain calcium but these may not be enough. For this reason, calcium supplement is often recommended to ensure good calcium balance.

The National Research Council cited that dogs fed with mainly meat diets result in major bone loss, pathological fractures, skeletal abnormalities and a condition called secondary hyperparathyroidism.

2. Nursing dogs

Mother dogs who are nursing puppies will have a higher need for calcium in their diet because they are losing large amounts in their milk. However, giving this supplement before delivery is not recommended as this can actually increase the risk of eclampsia.

During pregnancy you should feed her a high-quality growth or lactation diet instead of relying on high-calcium foods. Too much calcium can cause calcification of the soft tissues of the fetus as well as other birth defects.

3. Dogs with calcium deficiency

Another name for this condition is hypocalcemia. This problem can be caused by a range of reasons. The treatment of giving additional calcium depends on the cause and other factors.

What causes calcium deficiency

There are numerous reasons for hypocalcemia but the following are more well-known:

  1.     Kidney failure
  2.     Eclampsia
  3.     Hypoparathyroidism
  4.     Low body protein
  5.     Certain types of poison
  6.     Blood transfusions

1. Kidney failure

One of the more common reasons dogs suffer from lack of calcium is due to kidney failure.  When the kidneys are not working properly, they throw off the calcium and phosphorus balance in the blood resulting in increased phosphorus and kidney enzyme levels. 

Without healthy kidney tissues to play its role in this balance, the body is fighting a losing battle. Calcium is taken from the dog’s bones to balance the phosphorus. In the end this only demineralizes and weakens the bones.        

However, kidney failure can also cause the opposite of hypocalcemia, which is hypercalcemia. This is typically due to a renal secondary hyperparathyroidism.

2. Hypoparathyroidism

The parathyroid gland produces hormones that regulate blood calcium levels. Sometimes this gland can become injured during thyroid surgery, thus impairing its function. Sometimes it has to be removed due to cancer or overactivity, which is causing hypocalcemia.

3. Eclampsia

This is a condition that can affect nursing dogs whereby their blood calcium levels drop drastically. It usually occurs when the mother dog is nursing puppies that are 1 to 4 weeks old. The cause can be either due to

  • excessive loss of calcium from the mother to the developing fetal skeletons,
  • calcium supplementation during pregnancy,
  • producing milk after birth,
  • not receiving a balanced premium growth and development diet while pregnant and nursing, or
  • a hormonal problem with the parathyroid gland.

Small dog breeds such as Chihuahuas, Pomeranians, Toy Poodles, Miniature Pinschers and Shih Tzus are more prone to eclampsia. Eclampsia requires immediate medical attention. 

4. Low body protein

Some of the calcium in your dog’s body is bound to protein. Consequently, low protein levels in the body can result in low calcium levels.

5. Certain types of poison

Antifreeze (ethylene glycol) is the most deadly poison that affects calcium levels. Even tiny amounts, if ingested, can be deadly for a dog. This chemical causes calcium oxalate crystals to be produced and become stuck in the kidneys, causing acute kidney failure.

Certain plants contain insoluble calcium oxalate that can bind calcium in the body, resulting in hypocalcemia. These plants include rhubarb leaves, star fruit and English shamrock.

6. Blood transfusions

Only transfusion of red blood cells can cause calcium levels to drop.

Signs of calcium deficiency in dogs

To have a clearer understanding of the signs, it helps to know what calcium is for. This mineral is actually categorised as an electrolyte. That is why it helps the nervous system to function smoothly. Cells use calcium to send signals to the muscle, heart and brain.

Calcium also regulates the concentration of fluids in a dog’s cells. Therefore, it has a role in blood clotting or thickening. The most basic purpose is of course to form bones and teeth.

Here are some of the symptoms of calcium deficiency:

  1. bones are soft and easily broken
  2. muscle spasms
  3. restlessness
  4. stiffness or tetany
  5. panting a lot  
  6. convulsions
  7. disorientation
  8. aggression
  9. high fever
  10. lethargy

Symptoms 2 to 9 are displayed by nursing dogs affected by calcium deficiency.

Calcium rich foods

It helps to know the types of natural foods that are already rich in calcium, so that you don’t give your dog too much of it.

Dairy products

Milk and cheese contain high amounts of calcium, but they are not good for dogs in excess. Dogs generally lose the ability to digest lactose soon after they are weaned. This explains why so many of them are lactose intolerant.

Cheese has less lactose but it can have a relatively high percentage of salt and fat. The type with the least salt is mozzarella low-sodium cheese (according to the USDA). Different brands of cheese have varying levels, even for cottage cheese.

Small quantities of watered down milk or a slice of cheese are fine. But the minute your dog’s poop becomes runny or shows other signs of intolerance, it’s best to discontinue immediately.


Also a dairy product, it contains large amounts of calcium but it has no sodium and is lower in fat than cheese. Furthermore, it has beneficial bacteria which can help to regulate and improve a dog’s intestinal microflora. Just a dollop is good enough.


Bones are constructed mainly from calcium, so it naturally contains a lot of it. These should be uncooked and from select animal parts only. Cooked bones are not safe because they can splinter easily. Splintered bone is sharp which can become lodged in the throat or intestines then cause perforations.


On top of being rich in calcium, they offer omega-3 fatty acids as well as various vitamins and minerals. The best type of fish is sardine, salmon, tuna and trout. Be sure to cook it thoroughly then remove all the bones before feeding it to your dog.

Legume plants

Well-known legumes include alfalfa, clover, beans, peas, chickpeas, lentils, lupins, mesquite, carob, soybeans, peanuts and tamarind.

Good sources of calcium supplement

It can be a little tricky to calculate the exact amount of calcium in food. In instances where the dosage is a sensitive matter, it may be better to just add calcium supplements to a dog’s food. Here are a few natural sources:

  1. bone meal powder
  2. eggshell powder
  3. seaweed calcium
  4. coral calcium

When not to give calcium supplements

Do not use calcium supplements in pets with high blood calcium and hypercalcaemia. Calcium supplements should be used cautiously in pets with heart or kidney disease, or in pets receiving digoxin or calcitriol.

What I should do before giving my dog calcium supplements

1. Consult your veterinarian first

Read the next section to know why.

2. Check for drug interactions

The following medications should be used with caution when given with calcium: antacids, aspirin, azole antifungals, calcitriol, calcium channel blockers, cefpodoxime, digoxin, dobutamine, estrogens, fluoroquinolone antibiotics, levothyroxine, magnesium sulfate, neuromuscular blockers, phenytoin, potassium supplements, propranolol, sucralfate, thiazide diuretics, verapamil, or vitamin D analogs.

3. Check for interactions with other supplements

Vitamins, herbal therapies, and supplements have the potential to interact with each other, as well as with prescription and over the counter medications. It is important to tell your veterinarian about any medications (including all vitamins, supplements or herbal therapies) that your pet is taking.

What happens if I give my dog too much calcium?

Excess calcium can cause disorders and diseases such as deformations in the hip and osteochondritis dissecans, that is, cracks in the cartilage and bone of the joints.  Giant-breed dogs, in particular, are genetically more prone to develop osteochondrosis (a joint disorder) and hypertrophic osteodystrophy (a bone disorder).

Overdosing can cause vomiting and diarrhea or constipation, especially for some calcium supplements that come in tablet or tasty soft-chew forms.

Some calcium supplements may also contain Vitamin D3 which significantly increases absorption of calcium, and the risk of toxicity. That is why it is better to choose those that contain only calcium which don’t come with any vitamin Ds.

If the supplement comes with Vitamin D, overdosing can cause excessive thirst or urination, weakness, increased blood calcium, and acute kidney failure to develop depending on the dose ingested.

Best calcium supplement for dogs

Wholistic Sea Coral Calcium is made from coral calcium, which naturally contains 38% calcium and 72 trace minerals.  Because minerals are most effective when acting synergistically in the presence of other minerals, this product is able to deliver the most highly available and utilisable form of calcium.

Due to concerns about iodine and lead presence in Japanese waters, Caribbean-origin coral is chosen to produce this supplement. Of course, its raw material is gathered from the top parts of the reef to preserve the precious integrity of the reefs and ocean life.

Wholistic Sea Coral Calcium provides the following benefits:

  •       Helps strengthens immune system
  •       Easy to digest and highly absorbable
  •       Ideal 2:1 ratio of calcium/ magnesium
  •       Supports healthy bones & muscles
  •       Helps regulates body pH

How are calcium supplements given?

Calcium supplements can be in the form of a tablet, capsule, gel cap, powder or injection. The last option is given in a hospital setting.

Otherwise, calcium should be given with food, either just before eating or mixed into the food. This makes calcium powder the easiest to apply as this type can be mixed easily with dog food.

Calcium levels also need to be balanced with phosphorus.  Ideally, dogs should get 1.2 parts calcium for every 1 part of phosphorus. 

What if I miss giving my pet the supplement?

If you miss a dose, never ever compensate by giving your pet double or extra doses in the next meal. As mentioned earlier, calcium overdose can be dangerous. Just give the prescribed dosage the next time you remember.


For normal healthy dogs – whether puppies or adult dogs that are not pregnant – it is best to give them a balanced meal with natural sources of calcium, curated by an animal nutritionist. For example, ground eggshell from free range chickens that is carefully mixed with gently cooked or raw food.


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