According to Dr. Julia Whittington, exotics veterinarian at the University of Illinois Veterinary Teaching Hospital in Urbana, reptiles cannot absorb calcium from the diet efficiently without active vitamin D, also known as vitamin D3. Vitamin D3 helps the intestines absorb calcium from food. UVB light absorbed through the skin helps animals convert inactive vitamin D to active vitamin D3. Without proper sun or UVB exposure, pet reptiles can be deficient in vitamin D3 and therefore deficient in calcium.
Calcium is vital for bone growth and maintenance, muscle function, and metabolism. When blood calcium levels are low—a condition called hypocalcemia—an animal may suffer muscle twitches and lethargy. Low blood calcium can also lead to metabolic bone disease; to compensate for blood calcium deficiency, the body may utilize stored calcium from the bones to maintain blood levels. This can be serious problem for growing reptiles, causing poorly developed or soft “gumby” bones that are prone to fractures, according to Dr. Whittington. Long-term calcium deficiency can also lead to secondary hormonal problems involving the parathyroid glands that help regulate calcium levels.
To prevent hypocalcemia, owners need to understand how to supply both proper UVB light and adequate dietary calcium to their reptiles. Dr. Whittington explains that one common mistake owners make is using plant grow lamps to supply light for their reptiles. These lamps supply the UVA light needed by plants, but do not supply UVB rays. Many people put their reptiles near windows to get sunlight, unaware that plastic and glass block UVB rays. A proper set-up will allow UVB rays from a lamp to reach a reptile without any obstruction. Placing a mesh screen between the lamp and the animal, for example, will allow UVB rays through.
Of course, even if a reptile produces enough vitamin D3, plenty of dietary calcium must also be provided for a reptile to absorb what it needs. Some store-bought reptile foods, such as crickets, are low in calcium. Too much phosphorus can interfere with calcium absorption, so maintaining a proper calcium/phosphorus balance in the diet is also important.
If a reptile is diagnosed with hypocalcemia, the first step is to determine the cause. A veterinarian can rule out kidney disease, which causes calcium to be eliminated through urine. If the deficiency is caused by lack of calcium intake or absorption, the next step is to maintain proper hydration, decrease dietary phosphorus, and increase dietary calcium and UVB exposure. Calcium can be supplemented orally or can be injected. Also, injections of vitamins A, D, and E can help jump-start calcium absorption by the gut.
With metabolic bone disease, blood calcium levels may appear normal because calcium is taken from the bone to maintain normal levels. In this case, injections of the hormone calcitonin can help bring calcium back into bones, but only if blood calcium levels are sufficient.
Recovery from severe hypocalcemia or metabolic bone disease can be a slow process, but Dr. Whittington says that she has seen many animals recover. Of course, the best way to treat hypocalcemia is to prevent it by supplying ample calcium in the diet, maintaining a proper calcium/phosphorus ratio, and supplying a good source of UVB light.
If you have any questions regarding hypocalcemia, dietary calcium, or UVB light for your reptile, contact your local exotics veterinarian.