Iguana Metabolic Bone Disease
Metabolic bone disease (MBD) is a very common disorder in captive green iguanas. \n\nIt results from an imbalance in the metabolism of calcium and phosphorus, often aggravated by a lack of vitamin D3. \n\nBones gradually become fragile and...
What is it?
Metabolic bone disease (MBD) is a very common disorder in captive green iguanas. \n\nIt results from an imbalance in the metabolism of calcium and phosphorus, often aggravated by a lack of vitamin D3. \n\nBones gradually become fragile and deformed, as the body draws calcium from the skeleton to maintain normal levels in the blood. \n\nThis is one of the main causes of veterinary consultation in young iguanas that are poorly nourished or poorly exposed to light.
Key point
Serious illness if diagnosed late: it can lead to convulsions, multiple fractures and threaten the life of the iguana.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
The first signs are often subtle: the iguana becomes less active, eats less, and may appear limp or tired. \n\nAs it progresses, we observe swelling of the jaws (“rubber jaw”, soft to the touch), legs that become deformed, a hesitant gait or lameness. \n\nThe animal may have difficulty getting off the ground, climbing, or refuse to move due to pain. \n\nIn advanced forms, tremors, muscle spasms or real convulsions may appear, linked to a blood calcium level that is too low. \n\nFractures can occur spontaneously, even with gentle handling.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
The main cause is an unbalanced diet: excess phosphorus in relation to calcium, or insufficient calcium intake (plants poor in calcium, lack of supplementation). \n\nA lack of exposure to ultraviolet B (UVB) rays prevents the iguana from synthesizing vitamin D3 itself, essential for the absorption of calcium by the intestine. \n\nOther factors can make the disorder worse, such as underlying kidney disease that disrupts calcium and phosphorus metabolism.
Young, growing iguanas are most vulnerable because their calcium requirements are high. \n\nA terrarium without a suitable UVB lamp, or with a lamp that is too old or too far away, greatly increases the risk. \n\nA diet based on lettuce, fruits or plants poor in calcium (instead of green leaves rich in calcium) promotes the disease. \n\nA lack of exposure to natural sunlight (filtered, without glass) is also a significant risk factor.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian relies on dietary and lighting history, clinical examination (jaw, paws, spine) and x-rays to assess bone density and detect possible fractures or deformities. \n\nA blood test allows you to measure the levels of calcium, phosphorus and sometimes vitamin D, and to check the functioning of the kidneys.
Treatment
Management combines a gradual correction of the diet, appropriate calcium supplementation under veterinary supervision, and the installation or improvement of appropriate UVB lighting. \n\nIn severe cases with very low blood calcium, calcium supplementation by injection may be necessary urgently. \n\nNutritional support and sometimes limited restraint of the animal are useful while the bones solidify. \n\nSurgery is only considered in the event of a serious fracture, once the general bone condition has stabilized.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Prevention is based on three pillars: a plant-based diet rich in calcium with a good calcium/phosphorus ratio, appropriate calcium supplementation, and quality UVB lighting, renewed regularly according to the manufacturer's recommendations. \n\nOccasional access to natural sunlight, without UV-blocking glass, is beneficial. \n\nRegular veterinary checks allow early signs to be detected before deformities appear.
Possible complications
Without treatment, the disease can progress to irreversible bone deformities, multiple spontaneous fractures, inability to move or feed alone, and seizures linked to dangerously low blood calcium. \n\nIn the most serious cases, the outcome can be fatal.
When to see a veterinarian
The iguana eats less or becomes abnormally calm and prostrate.\nThe jaw appears soft, swollen or deformed.\nThe animal limps, has difficulty getting up or refuses to move.\nTremors, spasms or convulsions appear.\nDeformity of the legs, tail or spine is visible.
Prognosis
The prognosis is favorable if the disease is detected early and the diet and lighting are corrected quickly: young animals can recover a good quality of life. \n\nOn the other hand, already established bone deformities often remain permanent, and very advanced cases with convulsions or multiple fractures have a more guarded prognosis.
Frequently asked questions
Can an iguana fed only lettuce develop this disease?
Yes, lettuce is low in calcium and high in water. A diet based on it, without other plants rich in calcium or supplementation, strongly exposes the iguana to metabolic bone disease.
Is a regular UVB lamp enough?
No, you need a lamp specifically designed to emit UVB at a level suitable for reptiles, positioned at the right distance, and replaced regularly because its effectiveness decreases over time even if it still illuminates visually.
Can bone deformities disappear with treatment?
The deformities already present do not generally disappear completely, but early treatment can stop their worsening and improve the comfort of the animal.
Does this disease only affect young iguanas?
It is more common and more severe in actively growing young people, but adults who are malnourished or poorly exposed to UVB can also be affected.
References
AVMA — American Veterinary Medical Association
Content reviewed by the TunisieVet editorial team · Updated 27 September 2026
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