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Ultra-Violet lighting is one of the most important things you can provide for your iguana.

UV lighting is broken into three parts: UVA, UVB and UVC.

UVA (320-400 nanometers):

UVA is an important part of sunlight.  It can be found in small amount in regular household light.  It is capable of passing through normal windows.  Working from the Pineal Gland, reptiles exposed to UVA light show increased activity, socialization, appetite and basking behavior.  It generally makes them "feel" good, as it does in humans.

UVB (290-320 nanometers):

UVB is the most critical portion of the light spectrum for iguanas and other diurnal, sun-basking reptiles.  UVB is not found in normal household lighting or "full-spectrum" lighting.  It will not pass-through modern window glass, screen or Plexiglas.  It is for this reason that we are required, through good-husbandry practice to provide a good strong UVB source, either naturally, through unfiltered sunlight or artificially through the use of specialized lamps, specifically designed to emit high-levels of UVB.

UVB is used by the iguana to produce vitamin D3 in the skin, through a process called bio-photosynthesis, This vitamin D3 then converts to Active Vitamin D3 in the liver and kidneys and allows the iguana's digestive system to absorb much needed calcium from the digested food, thereby sending calcium (in serum form) through the blood stream and into the bone matrix.  This adds strength to the bone matrix, making the bones stronger and more flexible.  It also reinforces the nervous system, keeping it strong and healthy. See:

D-UV (290-305 nanometers):

Recent research has identified a further component in the UVB part of the spectrum called D-UV.  This specific portion of the UVB part of the spectrum has been shown to stimulate photo-biosynthesis, the natural process whereby the iguana converts the Vitamin D3 to Active D3.  Light in this range optimizes the process.  As we further research this phenomenon, we are realizing that not all UVB is created equally.  UVB higher than 305 nanometers actually initiates the self-limiting process of UVB absorption.  This means that the UVB in this range is broken down into biologically inactive products called Lumesterol and Tachysterol, which accumulate in the skin.  the key in artificial lighting is to offer the right amount of "good" UVB, thereby helping the iguana efficiently absorb calcium from the digested foods in the hind-gut.

UVC (180-280 nanometers):

UVC is harmful to all living cells.  In nature, it is filtered out by the Ozone layer in the atmosphere.  It is never required nor should be permitted in artificial lighting for both humans and reptiles.

For the most comprehensive and accurate information on the UV Spectrum, See:

Artificial UV Lighting:

Natural sunlight is the cheapest and best UV lighting you can provide.  Just an hour a day in natural, unfiltered sunlight can provide the necessary UV component to keep your iguana happy, healthy and strong.  Many of us do not have the ability to provide daily sunlight for our iguanas, so artificial lighting has been developed to assist in proper husbandry.

There are several different types of artificial lighting available for the iguana keeper.  We will discuss the two most popular types, Fluorescent and Mercury Vapor:

Fluorescent Lighting:

Fluorescent lighting comes in the familiar long, thin tubes we see elsewhere in our daily lives.  Fluorescent lighting is an adequate source of UVA and UVB for iguanas.  It's important that these lights be used properly, following these guidelines:

1) Purchase good-quality, proven fluorescent tubes.  We recommend Reptisun 5.0 or 10.0 manufactured by ZooMed®.  These lights have show to produce the best amount of UVA and UVB for Iguanas and other sun-basking reptiles and are readily available in most reputable pet shops.  For a complete comparison of readily available lighting, please see:

2) Use (2) of these lights in tandem to gain the maximum amount of UVB necessary.

3) Use a good-quality lighting fixture.  Low-cost fixtures have a lesser quality ballast that effects UV output form the lamps.

4) Increase UV output by using a fixture with a highly reflective surface.  Covering the reflector wings with common tin foil (shiny-side out) will increase UV output by 50%.

5) Place the fixture so that it is no farther than 6"-8" from the back of the iguana while basking.  The greater the distance from light to reptile, the less UVB is produced.

6) Replace fluorescent tubes every six-months as a general rule.  UVB weakens and disappears after about six-months.  It's important to realize that even though the tube is still producing light, there may not be any UVB left.  You can readily monitor the UVB amount by using a Solarmeter 6.2 UVB Radiometer.  This handy device will allow you to measure the UVB emissions in microwatts per centimeter squared (mW/cm2), allowing you to know exactly when the tubes have become so weak they need to be replaced.  This can save you money in the long-run as some tubes will produce UVB up to one year.  To learn more about the Solarmeter 6.2, see

Mercury Vapor Lighting:

The most recent advances in UV lighting, and a step up in the artificial lighting option, is the Mercury Vapor lamp.

These reptile lighting tools are not as readily available as fluorescent tubes and cost more money.  But they produce an incredible amount of UVA, UVB and D-UV, significantly higher than fluorescent tubes.

Mercury Vapor lamps are known to be fragile, burn out quickly and pose some dangers to the reptile and humans alike.  They should be used exactly as specified by the manufacturer and very responsibly.

Recent developments in Mercury Vapor lamp design has brought about changes that address these previously mentioned issues.  These include lamp designs that are more stable, last longer and project UVA and UVB much farther than tubes, making them more convenient for larger iguana enclosures.

The best Mercury Vapor lamps on the market are the "Westron Design", these are sold under the name ReptileUV Mega-Ray® and T-Rex Active UV-Heat®.  This new design provides a much more stable and sturdier lamp, which emits larger amounts of UVA and UVB, specifically in the D-UV range, at greater distances for a longer time.

There are two types of Mercury Vapor lamps: the popular self-ballasted (SB) and the newer externally-ballasted (EB).

Self-ballasted Mercury Vapor lamps provide UV and heat.  These lamps, though much more stable, are still prone to damage from jarring.  The Mega-Ray® brand offer a pro-rated 6-month guarantee, the only one of it's kind on the market today.  For light PLUS heat, this is the lamp to have.

Externally-ballasted lamps are the newcomer to the reptile lighting market and are offered exclusively through www.reptileUV.com.  These incredible lamps provide tremendous UVA and UVB, with little heat.  These remarkable lamps last longer than their SB cousins by virtue of the external ballast.  The ballast is what decays and fails in the SB versions, long before the lamp has stopped emitting UVB.  With the ballast used externally, the actual lamp can be replaced while the ballast will continue to perform for up to two years.  The warrantee is the best on the market, with 1-year for the lamp and 2-years for the ballast.  For the serious hobbyist, this is the lamp to have.

As with fluorescents, you should follow these guidelines when using Mercury Vapor lamps:

1) Purchase good quality, proven lamps.  Not all lamps are created equal.  Save the receipts in order to return failed lamps.

2) Follow all manufacturers recommendations for use.  Including mounting, placement and positioning.  This will greatly effect the lamps lifespan.

3) Do not place lamps closer than recommended distances.  This can be harmful to your iguana.

4) Do not place lamps where they are shining on high human traffic areas.  Just like the sun, you should avoid looking directly into the light and not be overly exposed to the UV.

5) Always monitor enclosure heat, especially with the self-ballasted style lamps.  Overheating at the basking shelf might cause the iguana to move away from the UVB source.

6) Mount securely and properly.  Like all lighting products, make sure the lamp is secure and will not fall over onto combustible material.

7) Replace the lamps at the recommended time stated by the manufacturer.  Use of a Solarmeter 6.2 UVB Meter will greatly increase the lifespan of the lamps, showing you exactly when to replace them.

Whichever lighting solution you choose, be sure to use it in the recommended manner and closely monitor lamp performance.  With proper use, you will be providing the best possible UV lighting for your iguana, adding health and happiness to a long life.