Addition issues that can occur in tame dragons are vitamin A deficiency and metabolic bone disease. Vitamin A deficiency is the shortage of vitamin A or carotenes. The dragon usually obtains vitamin A through the consumption of leafy greens and insects. This deficiency is found typically in tame dragons, since wild dragons have a surplus of greens and insects to eats. The lack of vitamin A can increase the parasitic issues, weakening the immune system, and can lead to the death of the dragon if the diet imbalance is not corrected. The metabolic bone disease is a product of lack of UVB light and calcium. Natural light gives off vitamin D3. This vitamin is vital to break down the calcium the dragon consumes, enhancing the importance of light. The disease can cause soft bones and muscle cramping (Langerwerf, 2006, p. 54-55). According to Langerwerf, signs of an unhealthy dragon include abnormal feces, inability to right itself when turned upside down, limping, sluggish behavior, refusing food, sunken eyes, vomiting, and weight loss (2006, p. 54).