Skink Metabolic Bone Disease
Metabolic bone disease (MBD) is a very common disorder among captive reptiles, including the sand skink. It affects the strength of bones. \nIt results from an imbalance between calcium, phosphorus and vitamin D3 in the animal's diet or env...
What is it?
Metabolic bone disease (MBD) is a very common disorder among captive reptiles, including the sand skink. It affects the strength of bones. \nIt results from an imbalance between calcium, phosphorus and vitamin D3 in the animal's diet or environment. \n Without sufficient intake or production of vitamin D3 (thanks to suitable UVB lighting), calcium is not properly absorbed by the intestine. \nThe skink's body will then draw calcium from its own bones to maintain a normal level in the blood. Bones gradually weaken, become deformed and can break easily.
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 skink moves less, eats less, seems tired. \nOver time, visible deformations of the legs, jaw or spine appear. \nThe animal may limp, have difficulty getting up from the ground, exhibit muscle tremors or spasms. \nIn advanced forms, fractures can occur spontaneously, even without apparent trauma, and convulsions or paralysis of the hind limbs are possible. \nThe lower jaw may become soft and deformed ("softened jaw bone"), making food intake difficult.
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 a chronic deficit of calcium relative to phosphorus in the diet (unbalanced calcium/phosphorus ratio), most often associated with a lack of vitamin D3. \nThis lack of vitamin D3 generally comes from insufficient exposure to UVB rays, which are essential for diurnal reptiles like the sand skink to synthesize this vitamin in their skin. \nA diet composed solely of unsupplemented insects (little calcium, a lot of phosphorus) greatly aggravates the imbalance.
Absence of a suitable UVB lamp or UVB lamp that is too old (useful radiation decreases over time even if visible light remains normal). \nPoorly lit terrarium, glass or plastic interposed between the animal and the UVB source (blocks UVB). \n Diet not varied, insects not sprinkled with calcium supplement. \n Young growing animals and breeding females, more exposed due to increased calcium requirements. \nUnsuitable terrarium temperature, disrupting digestion and metabolism.
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 the breeding history (type of lighting, diet, supplementation) and on the clinical examination of the animal, in particular the palpation of the long bones and the jaw. \nX-rays are used to assess bone density and look for deformities or fractures. \nA blood test can be useful to measure calcium and phosphorus levels, although blood values sometimes remain normal even in cases of already established illness.
Treatment
Treatment is primarily based on correcting the causes: provision of suitable UVB lighting and a balanced calcium diet. \nThe veterinarian can prescribe calcium and vitamin D3 supplementation, in a form and frequency adapted to the animal's condition. \nIn severe cases with fractures or inability to move, supportive care (rehydration, nutritional assistance, pain management) is put in place. \nSurgery is rarely indicated but can sometimes be considered for certain fractures.
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, adapted to the needs of the sand skink, and replace it regularly according to the manufacturer's recommendations. \nNever place glass or plastic between the animal and the UVB lamp. \nSprinkle the insects with a calcium supplement before offering them, at a frequency recommended by a veterinarian specializing in reptiles. \nOffer a varied diet adapted to the species. \nHave your skink checked regularly by a veterinarian who knows reptiles, especially young, growing ones.
Possible complications
Spontaneous fractures of the limbs or spine. \n Permanent bone deformities, even after healing. \nInability to eat properly in cases of severe jaw damage. \n Paralysis of the hind limbs, convulsions and in very advanced cases, death of the animal.
When to see a veterinarian
The skink moves less than usual or refuses to move.
It has visible deformation of the legs, back or jaw.
He limps or seems to have pain when moving.
He has tremors, muscle spasms or convulsions.
He no longer eats or visibly loses weight.
A leg or body part appears broken without obvious trauma.
Prognosis
The prognosis depends greatly on the precocity of treatment. \nDetected early, the disease can be stabilized and the animal can regain a good quality of life, even if certain bone deformations may remain visible. \nIn advanced forms with multiple fractures or paralysis, the prognosis is more guarded and recovery is often partial.
Frequently asked questions
My skink looks normal, can he still have this disease?
Yes. At the beginning, the signs are often very discreet: a little less activity or appetite. Deformities sometimes only appear when the disease is already advanced. Regular veterinary check-ups can detect it earlier.
Is a UVB lamp really essential in a terrarium?
Yes, in a diurnal species like the sand skink. UVB allows the skin to produce vitamin D3, necessary for the absorption of calcium. Without effective UVB, even a calcium-rich diet may not be enough.
Does terrarium glazing block UVB?
Yes, glass and most plastics block a lot of useful UVB rays. The lamp must illuminate the animal without any obstacle between it and the skink.
Can my skink fully recover?
It depends on the stage of the disease. If taken care of early, a clear improvement is possible. On the other hand, bone deformities that have been present for a long time do not generally disappear completely.
References
AVMA — American Veterinary Medical Association
WSAVA — World Small Animal Veterinary Association
Content reviewed by the TunisieVet editorial team · Updated 27 September 2026
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