UV light for chameleons

Keeping chameleons in captivity failed in the past due partly to a limited understanding of their need for ultra violet light. Sadly, the situation has only improved slightly today and the need for UV light for chameleons is too often ignored.

I still get photos of Veiled chameleons with chronic MBD from owners who thought they could get away without a UV light. They write to ask how they can ‘fix’ their pet’s MBD. In most, if not all, cases they can’t.

The correct use of UV light is essential for a healthy chameleon. But it may not be as straightforward as you think. Read on to learn why distance and strength can play a critical part.

Know your UV

UV light for chameleons showing wavelength
UV light wavelength compared to other light

There are three types of ultra violet light: UV-A (long wave), UV-B (medium wave) and UV-C (short wave).

UV-A is part of the chameleon’s visible spectrum. It allows it to see its surroundings in a slightly different way to humans but it is UV-B that is important for vitamin D3 synthesis in reptiles. UV-B has a wavelength in the range of 290 to 320nm (nanometres).

UV-C is harmful and is used in ultra violet sterilisers.

The process of vitamin D3 synthesis in the skin as a result of exposure to ultra violet light involves complex topics such as PTH (parathyroid) hormones and pre-vitamin D3 conversion.  As such, these are outside the scope of this blog. It’s enough to repeat: UV light is essential for a healthy chameleon. It’s also crucial if a female is to lay viable eggs.

Generally, a UV light for chameleons does not produce heat. It should not be confused with other types of lighting, such as basking or Infra-Red lights.

The sun – the perfect UV light for chameleons

The cheapest source of UV-B is the sun. This is obviously far better than any artificial source.  Anyone who has read any of my books or blogs elsewhere will know I’m a huge advocate of exposing chameleons to natural sunlight. But only in the right location and situation. Obviously, you must exercise common sense how you expose your chameleon. And not all climates are suitable.

Even a few hours outdoors each week will be beneficial.  In South Africa, it was my habit to place my chameleons outside as much as possible, even in the winter.  Unless the temperatures were below 16°C, I would put my Panther chameleons outside against a sunny wall and out of any cold winds during the middle of the day.

In Malaysia, I keep my adult Veiled chameleons outside 24 hours a day. However, the cages are placed so they get a mix of sun and shade. Daytime temperatures in the open can reach 36°C but inside the cages it rarely goes above 32°C.

The cages house small bushes so the chameleons can crawl among the leaves to escape the sun if they wish. An automated watering system helps keep the bottom of the cage moist and at a lower temperature, even on hot days.

Not all species would be survive outside in a hot, tropical climate.

There are subtle differences in behaviour under artificial light compared to natural sun light.  Studies show that in the wild chameleons can regulate their ultra violet light exposure, moving in and out of the sun as required.

How much UV is natural?

Under artificial light, there is evidence that some species are attracted to the ultra violet light a bit like moths. This may mean they do not regulate their exposure as they would in the wild.

This is not necessarily as bad as it sounds when one compares outside UV and that from a UV light using a UV meter.  On a sunny day at noon in Gauteng, a UV meter might read 450 mW/cm2. This may be reduced by cloud or by taking the reading earlier or later in the day but it is still quite intense.

UV light for chameleons showing wavelength
UV light emission from a 5.0 ReptiGlo UV light.

It is worth noting that the altitude on the Highveld (between 1,500 and 1,700 metres above sea level) results in meter readings higher than at sea level. At lower altitudes a reading of 300mW/cm2 might be normal at noon on the equator.  For comparison, a 5.0 ReptiGlo UV light for chameleons will register roughly 17 mW/cm2 at 30 cm from the tube.

Does this comparison mean that either a stronger light is needed indoors or that artificial light is ineffectual? No. If used correctly artificial light can be quite sufficient and beneficial. Using a stronger light would probably result in health issues, including eye damage.

UV Strength

The key thing to remember is the strength of the light falls off with distance from the source.  The following chart for a 5.0 UV tube, shows this clearly:

Strength of the UV as distance from the light  increases
Distance in cm 5 10 15 20 25 30 35 40 45 50
mW/cm2 100 54 37 28 22 17 14 13 11 9


From this chart it can be seen that at 30cm the strength of the light is 17 mW/cm2.  Research and experience show this is an acceptable reading for captive chameleons.

But the chart shows the further down the cage the chameleon travels away from the light source, the lower the ultra violet intensity. By 50cm the light is barely producing any worthwhile UV light.

UV lights for chameleons when they are small
UV lights above baby chameleons. Note the ends overlap to make up for reduced UV.

Another point to bear in mind is that the last few centimetres at each end of the tube produce far less UV than the middle. Therefore, always use the longest tube you can for your cage.

The majority of UV lights on sale in South Africa as tubes normally have an effective lifespan of about nine months. I’ve tested several with a UV meter during use and found some still producing ultra violet at full strength several months after this. However, unless you’ve invested in a UV meter it’s better to assume that nine months is the limit.


If you’re planning on keeping a chameleon, it is essential you invest in UV lighting. If you skimp on this you will end up with a sick chameleon. The only alternative is exposure to direct natural sunlight.

Keeping a chameleon in a window will not work. When the sun hits the window, the temperatures in the chameleon cage are likely rise very quickly. Never put a glass cage outdoors, even with the lid off.

Most types of glass filter out the UV light for chameleons. That means that most conservatories and glasshouses will not work unless special glass is used.

The information shown above is for the ‘normal’ chameleons kept in captivity, e.g. Veiled, Panther, Carpets, etc.  Veiled chameleons are especially prone to MBD and poor UV light is often a direct cause.

There are species that are not as dependent on UV, for example, certain Brookesias that spend their time on the forest floor. Montane species may come from areas with intense cloud cover but when it breaks, the altitude can mean the UV intensity is high. A normal UV set up should be used unless you find evidence to show the species has specific requirements.

UV light for chameleons is essential to avoid MBD
Chameleon suffering severe MBD due to lack of UV lighting