Adequate UV-B lighting is essential for the health and welfare of many companion reptile species, yet deficiency remains among the most common preventable welfare problems in reptile keeping.
UV-B deficiency in reptiles causes suffering that is slow to develop and easily missed until it becomes severe. Metabolic bone disease progresses over months, causing progressive weakness, difficulty moving, and eventually fractures and neurological signs from calcium deficiency affecting muscle function. By the time clinical signs are obvious, significant welfare harm has already occurred. The insidious nature of the condition — developing slowly under seemingly adequate conditions — makes prevention through correct lighting setup and regular lamp replacement critical. The UV-B requirements of different species vary enormously and are frequently underestimated in basic care sheets. A tortoise basking in UV Index 3 light from a lamp placed 60 cm away may receive far less than the UV Index 6-8 recommended for its species. Accurate measurement tools make appropriate provision achievable and should be standard equipment for reptile keepers.