Fibrose osteodystrofie or Metabolic Bone disease is a common problem with Iguanas. It can be described as a deformity on the bone structure.

The most common food-related diseases with Iguanas are caused by food with a low potassium rate or a high phosphor-rate and/or a shortage of vitamin D3. Bugs, a lot of vegetables and fruit are very low on potassium and vitamin D3. Because the animals spend most of their time indoors, normal synthesis of the vitamin D3 is blocked. A daily dose of UVB-radiation is necessary for the formation of vitamin D3 with Iguanas. Insufficient exposure to ultraviolet light in the wave area of 290-315 nanometers will cause MDB. Vitamin D3 ensures the absorption of potassium from the stomach- and colon area and will balance the potassium- and phosphor-levels. When the Iguana suffers from a shortage in potassium it will extract potassium from its own bones. This will make the bones rubbery and fragile. MDB can also be caused by kidney inflictions.


lethargic behaviourlethargic behaviour

A poorly adapted diet is one of the many causes of MDB. It is very important to select fruit and vegetables with the correct potassium/phosphor ratio. The recommended ratio with Iguanas is 2:1. Other than that there are different kinds of vegetables with a high concentration of oxalic acid. Ex.: rhubarb, spinach and beetroot. This oxalic acid can prevent the Iguana from extracting a sufficient amount of potassium from the colon; this will lead to an insufficient flow of potassium from the digestive system to the blood.


Perceptible symptoms:

  • a soft trembling of the toes
  • a spastic, shaky way of moving
  • shaking, convulsions of the paws, toes or muscles in the body when in rest
  • shaking and trembling when being held
  • lazy behavior
  • swelling of the lower jaw or a very soft lower jaw
  • nicks in the tail
  • an unusual posture (ex.: low on its paws when walking)
  • swollen limbs
  • hard bumps or swelling of the long bones in the paws
  • bumps along the spine and tail
  • softening of chest and/or back
  • not being able to seal the beak completely
  • dragging across the ground and the lack of strength to climb and hold on properly
  • Also bone fractures, anorectic behavior and constipation may be an indication of MDB.


IT is very important to handle an Iguana with MDB as infrequent as possible to prevent bone fractures and their complications. Also climbing rocks, branches and the cork on the back of the terrarium need to be removed. During the treatment it is advised to examine and weigh the Iguana weekly. The careful watching of the Iguana’s physical condition, especially in the beginning of the treatment, is very important to monitor its progression.

A slight case of MDB is when there are only sensible and barely visible symptoms. When you have not seen the trembling and feel the disfigurements on the bones, the reptile is in a relatively severe condition. A mild case can often be treated by optimal care; this means the correct nutrition and a well-adapted terrarium. When you have the possibility to expose the Iguana to direct sunlight for half an hour a day, please do so. Do remember that glass or plexi don’t let through the UVB radiation. A sever case can reflect all the above named symptoms. In this case a more intense training is required. X-rays and blood exams can help to determine the severity of the situation.

When there is a fracture it is common to fix the fracture externally because the weak bone structure prevents internal fixation. When there are more broken bones or a broken back- or neck-bone fixation might not be an option. Rest in an adapted terrarium without any climbing possibilities and the treatment of the metabolism problems (potassium) that goes together with this condition, will resolve the general orthopedic problems.

Every stadium of MDB should be treated in the same way First potassium will be injected, when orally provided; it should be complemented with oral vitamin D3. An adaptation of the nutrition is at hand and often the reptiles will have to be forced to eat. The easiest way to do this is to use a preparation with added minerals and vitamins. Ex.: Olvarit baby nutrition, nutrilon soja, cat- or dog food, parrot food. A vet can help you with the dosage and the duration of the treatment and the choice of food.

Then there are often occurring infliction that needs to be treated like an inflammation of the mucus in the beak and abscesses on different parts of the body.

An Iguana can suffer from longtime and even permanent consequences of MDB. Vertebrae-inflictions like scoliosis (bends the vertebrae) and kyphosis (the back is hollowed out backwards) can be present at the time of the diagnosis and worsen as time passes. Deformities of the lower jaw can become more explicit when the Iguana grows and can prevent the Iguana from eating on its own. The Iguana will then have to be fed or even have an operation.
It is very important to consult a vet as soon as possible and determine a way of treatment. In general MDB is not a life-threatening problem when it is caught in time and treated properly. De deforming on the skeleton are permanent. Other than that potassium can be stored in the kidneys, the stomach and the lungs; this may not be an immediate problem, but it can eventually lead to chronic kidney failure and eventually death.

Author, Evert Henningheim
Elliot R. Jacobson, DVM, PhD, DACZM (2003) Biology, Husbandry, and Medicine of the Green Iguana. Original edition., Krieger Publishing Company, Malabar, Florida, USA.

Source: Dr. Marja Kik, veterinarian for reptiles