Introduction to UV Lighting Requirements for Reptiles

Proper lighting is an essential part of a reptile’s environment. It is vital for the reptile’s overall health, including feeding behavior, activity level, and skin maintenance.  Because captive reptiles are not exposed to adequate levels of sunlight, their housing system must be equipped with a source of full-spectrum ultraviolet (UV) light that will provide them with the proper type and amount of light that they need to be healthy.  All diurnal (active during the day) and some nocturnal (active at night) reptiles will require UV lighting.

Types of lighting:

The best source of ultraviolet rays for reptiles is natural sunlight. The problem with using natural sunlight as your reptile’s source of UV rays is that reptiles are most often kept in glass or plastic enclosures.  Even if you were to keep your companion reptile in an area where it will be exposed to lots of sunlight, not all wavelengths of UV rays are able to penetrate through glass and plastic. This is why bulbs that produce UV rays are essential to a companion reptile habitat.

When purchasing a light for your companion reptile’s housing system, it is important to select the correct type of bulb. Some bulbs may not produce the correct type of light and, therefore, will not provide the reptile with the full-spectrum light it requires. The best type of bulb to purchase is a fluorescent bulb that produces UV wavelengths from 290 to 320 nanometers.  Mercury vapor lamps are the only other light source that can produce these wavelengths.

The bulbs should be placed near areas where the reptile will rest or bask to ensure that it is getting as much UV exposure as possible. It is recommended that the UV lights are placed within 18 inches of these areas, while mercury lamps can be placed within several feet of them.


Photoperiod refers to the daily cycle of light and darkness in your reptile’s enclosure.  It affects the reptile’s physical functions and behavior. All animals have a specific photoperiod to which their body responds. For reptiles, there are daily photoperiods and annual photoperiods. Changes in photoperiod over the course of the year evoke changes in a reptile’s behavior and physiological function. For example, an increase in hours of light may cause reptiles to begin to engage in reproductive activity, while a reduction in hours of light will signal to the reptile that reproduction is not advantageous at that time.

As a reptile owner, it is important to know the photoperiod that your companion reptile would experience in its natural environment. By following the same schedule, you will be able to maintain your reptile’s natural biological clock. Most reptiles’ photoperiods depend on what type of climate they live in, which determines how many hours of light and how many hours of dark they are exposed to.

Tropical and subtropical reptile species should be exposed to 14hours of full-spectrum light during the summer and 10 hours during the winter. Temperate species should be exposed to 16 hours of full-spectrum light in the summer and eight hours in the winter.

The importance of ultraviolet light to nutrient metabolism:

Ultraviolet lighting is also critical for maintaining normal levels of several key vitamins and minerals.  Vitamin D plays an important role in the metabolism and balance of calcium in most living organisms. When an animal does not receive the proper amounts of vitamin D, its health will deteriorate. Vitamin D3 is the most biologically active form of vitamin D and is synthesized from cholesterol. Ultraviolet light is required for this synthesis to occur. Most animals, including humans, are able to get enough UV light for adequate amounts of vitamin D3 to be synthesized by being exposed to natural sunlight for a small period of time each day. Many companion animal diets are also supplemented with vitamin D.

Providing UV light to your reptile enables vitamin D3 synthesis, which means that calcium will be properly digested and stored. Along with UV light, it is recommended that a supplement should be added to your companion reptile’s diet. A powdered vitamin and mineral supplement is often used when crickets or other types of insects are the main food source for a reptile. Placing the crickets in a plastic bag that contains the powder and then shaking the bag will allow for the crickets to become coated in the powder. 

When vitamin D, calcium, or phosphorous blood levels are below normal, the regulation of calcium, phosphorous, and magnesium levels in the blood and bone is affected. This is why symptoms of a vitamin D deficiency will manifest themselves mainly in bone problems. Reptiles with a deficiency will develop weak and spongy bones. This condition is known as metabolic bone disease. Many owners will notice that their reptile’s jaw bones seem swollen. This is actually caused by the fact that the bone has become so soft and weak that the muscle is pulling it outward, making it appear swollen. Many animals with this condition will not be able to eat on their own because their jaw bones are so weak. If you notice that your companion reptile is unable to feed itself, has bone deformities, or is displaying other symptoms or abnormal behavior, contact your veterinarian.             

It is important to understand the type of lighting your specific species of reptile needs and its ideal length of light cycle.  If you intend to breed your reptile, photoperiod and proper UV lighting are even more critical.  Changes in photoperiod will induce mating season in the reptile and UV light for vitamin D synthesis is necessary for bone and egg development and formation. 

Lisa Karr-Lilienthal, Ph.D. & Kaycee Points -University of Nebraksa-Lincoln