Metabolic bone disease of the wall lizard
Metabolic bone disease (MBD) is a very common disorder among reptiles kept in captivity, including the wall lizard. It affects the skeleton which becomes fragile and gradually deforms. This disease is not caused by a microbe: it results fro...
What is it?
Metabolic bone disease (MBD) is a very common disorder among reptiles kept in captivity, including the wall lizard. It affects the skeleton which becomes fragile and gradually deforms. This disease is not caused by a microbe: it results from a nutritional imbalance and a lack of exposure to appropriate light. Without treatment, it can make the animal unable to move normally and threaten its life.
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 discreet: the animal moves less, seems stiff or tired. \n\nOver time, the legs and jaw may become deformed, swollen, or appear "rubber-like" as the bones lose their normal rigidity. \n\nWe may observe lameness, difficulty climbing or standing up, trembling of the limbs, or even episodes of spasms or convulsions in advanced forms. \n\nAppetite often decreases, and the lizard may have difficulty catching or swallowing prey if the jaw is affected. \n\nIn severe cases, the animal remains prostrate, unable to rise on its legs.
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 imbalance of calcium and phosphorus in the diet, often compounded by a lack of vitamin D3. \n\nThis vitamin is essential for the intestine to properly absorb calcium; However, it is normally produced by the lizard's skin under the effect of ultraviolet B (UVB) rays from the sun. \n\nIn captivity, if the terrarium does not have suitable UVB lighting or if it is too old and ineffective, the lizard cannot produce enough vitamin D3, even if its diet contains calcium. \n\nThe body then compensates for this lack by drawing calcium from the bones, which gradually weakens them.
Absence or poor quality of UVB lighting in the terrarium.\n\nDiet consisting solely of insects not supplemented with calcium ("naked" prey).\n\nImbalance of the calcium/phosphorus ratio in the given prey (crickets, worms, etc. naturally rich in phosphorus).\n\nAbsence of heat bathing area ("basking") allowing good thermoregulation, necessary for calcium metabolism.\n\nYoung animals in growth or pregnant females, whose calcium needs are higher.\n\nLack of direct solar exposure not filtered by glass (glass blocks UVB).
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian specializing in exotic animals carries out a complete clinical examination, observing the posture, the flexibility of the bones (especially the jaw and legs) and the gait of the animal. \n\nX-rays allow you to visualize bone density and look for deformities or fractures. \n\nA blood test may be offered to assess calcium and phosphorus levels, although this remains technically delicate in such a small animal. \n\nThe veterinarian also questions the owner about the breeding conditions: type of lighting, diet, supplementation, to identify the origin of the imbalance.
Treatment
Management is primarily based on correcting captivity conditions: installation or replacement of UVB lighting, adjustment of diet and calcium and vitamin D3 supplementation. \n\nIn more advanced cases, the veterinarian can prescribe appropriate calcium supplementation, in injectable or oral form depending on the severity. \n\nSupportive treatment (fluid therapy, pain management) may be necessary if the animal is very weakened or has convulsions. \n\nHealing existing bone deformities is not always possible, but early correction often stops the worsening and restores a better quality of life.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Install quality UVB lighting, suitable for daytime lizards, and replace it regularly even if it is still illuminating (UVB emission decreases over time without the visible light decreasing).\n\nRegularly sprinkle the prey (crickets, worms, fruit flies) with a calcium supplement before giving them to the lizard, varying the intake according to age and stage of life.\n\nOffer a varied diet to limit the deficiencies.\n\nArrange the terrarium with a thermal gradient and a heating zone allowing the lizard to regulate its body temperature.\n\nHave the installation of the terrarium and the state of health of the animal checked regularly by a veterinarian who knows reptiles.
Possible complications
Spontaneous fractures of weakened bones, even during normal movements.\n\nPermanent deformities of the spine, legs or jaw.\n\nLong-lasting difficulty feeding if the jaw remains deformed.\n\nConvulsions and neurological disorders linked to a severe drop in blood calcium, which can be life-threatening.\n\nProlonged immobilization favoring other secondary disorders (bed sores, infections).
When to see a veterinarian
The lizard moves less than usual or appears stiff.\nThe legs or jaw appear soft, swollen or deformed.\nThe animal limps or has difficulty standing up on its legs.\nTemblors or spasms are observed.\nThe appetite decreases or the animal is no longer able to catch its prey.\nThe animal remains lying down and is no longer able to get up.
Prognosis
The prognosis depends greatly on the precocity of treatment. \n\nDetected early, with rapid correction of lighting and diet, the evolution is often favorable and the animal can return to a normal life. \n\nOn the other hand, if the disease is diagnosed at an advanced stage, with marked bone deformities or convulsions, the after-effects can be permanent and the prognosis becomes more guarded.
Frequently asked questions
Does the wall lizard really need UVB in captivity?
Yes. Even if it lives outside in the wild, in a terrarium it depends entirely on the UVB lamp to produce its vitamin D and absorb calcium correctly.
Is giving lots of calcium enough if I don't have a UVB lamp?
No. Without sufficient vitamin D3, ingested calcium is poorly absorbed by the intestine, regardless of the quantity given. The UVB lamp remains essential, except in the case of direct vitamin D3 supplementation validated by a veterinarian.
Can you treat a lizard whose legs are already deformed?
We can often stop the deterioration and improve the comfort of the animal, but the bone deformities already established generally do not disappear completely.
How do I know if my UVB lighting is still effective?
UVB tubes lose their effectiveness over time even though they still illuminate visually. It is advisable to replace them according to the manufacturer's recommendations, generally several times a year to one year depending on the model, and to seek advice from a veterinarian or reptile specialist.
References
AVMA — American Veterinary Medical Association
Content reviewed by the TunisieVet editorial team · Updated 28 September 2026
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