Calcium Supplements

By Rania Gollakner, BS, DVM, MPH

What are calcium supplements?

Calcium supplements are various forms of calcium used to treat or prevent low calcium blood levels (hypocalcemia) in many species. Calcium with lactate, citrate, ascorbate, carbonate, gluconate, or phosphate may be available. Bone meal has also been used as a calcium source; however, the effects are similar when compared to the manufactured supplements and bone meal may contain undesirable components. Calcium derived from coral is not recommended due to environmental concerns.

Commercially prepared diets for pets are complete and balanced, and do not need additional calcium supplementation under normal circumstances. Use of calcium supplements may be required when feeding a homemade diet, or in pregnant or nursing pets. Calcium supplementation should only be used under veterinary supervision, as too much calcium can cause other health problems.

What are dietary supplements?

Dietary supplements are substances that can be used to supplement the diet, such as vitamins, minerals, amino acids, herbs, botanicals, enzymes, and probiotics. While many supplements are sold over the counter, they still contain ingredients that have biological effects that should be managed by your veterinarian. Follow your veterinarian’s directions and cautions very carefully as their directions may be significantly different from those on the label.

There are differences in how countries regulate supplements. In the United States, these substances are not as vigorously regulated by the FDA as other medications, which means they can be sold without the manufacturer proving their effectiveness, safety, and without a guarantee of consistent or accurately reported ingredients. In Canada, products that have been evaluated for quality, safety, and effectiveness by Health Canada and authorized for sale will have a license number on the label.

How effective are calcium supplements?

Calcium supplements are very effective when used properly to treat low blood calcium or to satisfy the daily dietary intake requirement.

How are calcium supplements given?

Calcium supplements are given by mouth in the form of a tablet, capsule, gel cap, or powder. They can also be given by injection in the hospital setting. Calcium should be given with food, either just before eating or mixed into the food. This medication should take effect within 1 to 2 hours; however, effects may not be visibly noticeable and therefore laboratory tests may need to be done to evaluate this medication’s effectiveness.

What if I miss giving my pet the supplement?

If you miss a dose, give it when you remember, but if it is close to the time for the next dose, skip the dose you missed and give it at the next scheduled time, and return to the regular dosing schedule. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

When used at appropriate doses, calcium supplement side effects are uncommon but may include constipation. When doses are too high, it can lead to deficiencies of other nutrients, bone development abnormalities, bladder stone development, or mineralization (hardening) of the soft tissues, and lead to changes in drinking or urination habits, vomiting, lack of appetite, or weakness.

This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this supplement?

Do not use calcium supplements in pets with high blood calcium. Calcium supplements should be used cautiously in pets with heart or kidney disease or in pets receiving digoxin or calcitriol. Use during pregnancy or in nursing mothers has not been specifically studied, but is generally considered safe when used at proper doses and under the guidance of your veterinarian.

Are there any drug interactions I should be aware of?

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.

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.

Is there any monitoring that needs to be done with this supplement?

Your veterinarian may monitor your pet to be sure that the medication is working. This will include monitoring blood calcium levels. Other mineral blood levels, parathyroid hormone, kidney values, and urine calcium levels may also be monitored.

How do I store calcium supplements?

Most formulations should be stored at room temperature around 77°F (25°C) and protected from freezing.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.

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