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Last updated January 1, 2014

Tetany in Reptiles

Muscle twitching caused by calcium deficiency

Melissa Kaplan, 12/30/2003


One of the hallmarks of moderate to severe metabolic bone disease (MBD) in animals, including reptiles, is muscle twitching, typically seen in the toes and legs.

Tetany occurs when the concentration of calcium ions (Ca++) in extracellular fluids (such as plasma) falls below normal. Calcium plays an important role in the proper functioning of the central nervous system, in cardiac and other organ functioning, in digestion, and in reproduction, as well as in building and keeping bones strong.

When the body is not getting enough calcium, the effect on the nervous system is to create a state of increasing hyperexcitability of the nerves. The nerves spontaneously discharge, sending impulses to skeletal muscles, which in turn results in the spasmodic contractions we tend to call "twitching."

Mild tetany is characterized by tingling in the fingers, toes, and lips. Since animals cannot tell us when they are experiencing these symptoms, and they may not initially alter the animal's behavior, pet owners may not see any signs of mild tetany unless their pet begins to show signs of favoring one or more feet, or perhaps rubbing or scratching at their mouth.

Acute tetany is where we see the muscular contractions, the twitches and tremors. Cramping may also occur in various muscles, and perhaps in the gut (as prolonged calcium deficiency will affect the gut's ability to function, ultimately causing the digestive processes to shut down). Left untreated, advanced severe tetany and cramping can lead to death, in humans and in animals.

In captivity, we see this most often occurring in lizards such as green iguanas, whose diets are often deficient in calcium, or their bodies are denied adequate exposure to UVB, resulting in their not being able to make enough pre-vitamin D and so cannot properly metabolize sufficient amounts of calcium to provide for all of their body's needs.

Abnormally low extracellular calcium ion concentration may also be caused by the parathyroid glands not able to produce or release enough release parathyroid hormone, the substance responsible for the regulation of calcium concentration in the body. Bodily fluids that are highly and persistently alkaline (pH over 7) can also result in severe tetany; this may be as a result of persistent vomiting, rapid breathing, or excess activity of aldosterone, a naturally occurring hormone that plays a role in electrolyte balance.

In the case of tetany caused MBD, the environment and diet need to be corrected in all cases. Depending on how severe and prolonged the MBD is, the pet may require injections of vitamin D and/or calcium, and may require boosted levels of oral calcium supplementation until the serum calcium levels are normalized and the body has resumed normal functioning.



Tetany is at the root of the disease named tetanus, caused by the bacterium Clostridium tetani.

Magnesium is an important co-factor in calcium metabolism. Magnesium deficiency may also cause tingling, numbness, shooting pains, cramping and twitching of hands, feet and toes, as well as cramping and twitching of the legs. Magnesium deficiencies are rare in reptiles such as green iguanas, as, when fed a proper diet, they will obtain sufficient magnesium.

A poor diet can lead to deficiencies in magnesium and other calcium metabolism co-factors, so the importance of feeding a healthy diet, and using appropriate multivitamin and mineral supplements as needed to assist the pet through high need periods (growth and development; reproduction; recovery from illness, injury, surgery, acute stress), cannot be stressed enough.

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