The best UVB bulb for a leopard gecko is a low-output linear tube, specifically the Arcadia ShadeDweller Pro T5 7% or the Zoo Med ReptiSun 5.0 T8. Both produce the gentle levels of UVB that match what leopard geckos encounter in the wild as crepuscular shade dwellers. The right choice between them depends on your enclosure height and your gecko’s morph.
Why Leopard Geckos Need UVB
There’s a persistent idea that leopard geckos don’t need UVB because they’re active at dawn and dusk rather than in full sun. Research has put this to rest. A study on leopard geckos confirmed that individuals exposed to UVB had significantly higher blood levels of vitamin D3 (61 nmol/L compared to 38 nmol/L in unexposed animals), proving they synthesize vitamin D through their skin just like diurnal reptiles do.
Vitamin D3 regulates calcium and phosphorus absorption. Without enough of it, leopard geckos develop metabolic bone disease, a painful condition that causes soft bones, deformities, tremors, and difficulty moving. While D3 powder supplements help, UVB lighting lets your gecko regulate its own vitamin D production naturally, which is closer to how it would live outside a tank.
The Target UVB Level
Leopard geckos fall into Ferguson Zone 1, the lowest UV category. This means their target UV Index at the basking spot is 0 to 0.7, with a maximum of 1.0 to 1.4 if they choose to sit closer to the light. For practical purposes, you want a UVI of roughly 1.0 at whatever surface your gecko basks on. Anything above 2.0 at that distance is too strong.
This is a much lower requirement than bearded dragons or other sun-loving species. It’s why you need a bulb specifically designed for low output rather than a powerful desert-style UVB tube.
Best Bulb Options
Arcadia ShadeDweller Pro T5 7%
This is the most popular choice among experienced keepers. Arcadia designed it specifically for Ferguson Zone 1 and 2 species. It’s a T5 tube, meaning it’s slimmer and more efficient than older T8 bulbs, but tuned to a lower output appropriate for shade dwellers. Mount it 10 to 15 inches from your gecko’s basking area to hit the right UVI range. The bulb packaging states a minimum distance of 10 inches from the animal.
Zoo Med ReptiSun 5.0 T8
The ReptiSun 5.0 is a solid alternative, especially if your enclosure is shorter. T8 bulbs are physically larger and produce slightly less intense output than T5 bulbs at the same distance, which can actually be an advantage for a species that needs very little UV. If your basking surface is closer than 10 inches to the top of the enclosure, a T8 like this is the safer pick.
How to Choose Between Them
There’s no universal winner. The deciding factor is the distance from the bulb to your gecko’s basking spot. Check the manufacturer’s UVI charts (available on both Arcadia’s and Zoo Med’s websites) and find which bulb delivers a UVI around 1.0 at your specific distance. A bulb that’s perfect at 12 inches could be too weak at 18 or too strong at 6.
Avoid Compact Coil Bulbs
Compact or coil UVB bulbs (the kind that screw into a standard lamp fixture) are not recommended for leopard geckos. These bulbs concentrate UV into a narrow beam rather than spreading it across the enclosure, which can cause eye irritation, photokeratoconjunctivitis (essentially a sunburn on the eyes), and skin burns. Linear tube bulbs distribute UV more evenly and create a natural gradient your gecko can move in and out of.
Mesh Tops and UVB Loss
If your UVB bulb sits on top of a metal screen lid, expect to lose 30% to 50% of the UV output before it reaches your gecko. That’s a massive reduction that can push an already low-output bulb below useful levels. You have two options: mount the bulb inside the enclosure using a fixture designed for interior mounting, or account for the screen loss by positioning the bulb closer or choosing a slightly stronger tube. Interior mounting is the more reliable approach since you can reference the manufacturer’s distance charts directly.
Adjustments for Albino Morphs
Albino leopard geckos and other lightly pigmented morphs (Tremper albino, Bell albino, Rainwater albino, blizzard, and similar) are more sensitive to UVB and can develop burns or eye problems at levels that are fine for normal morphs. For these animals, use a weaker T8 bulb instead of a T5, increase the distance between bulb and basking spot, and aim for the lower end of the UVI range. Make sure your enclosure has plenty of shaded hides so an albino gecko can fully escape the UV when it wants to. The goal is to offer UV as an option, not flood the entire tank with it.
How Long to Run the Light
Run your UVB bulb on the same schedule as your daytime heat and visible light, typically 12 hours on and 12 hours off during summer months, shifting to around 10 hours on and 14 hours off in winter. This mimics the natural seasonal light cycle leopard geckos experience in their native range across Afghanistan, Pakistan, and northwest India. A simple plug-in timer keeps this consistent without daily effort.
Bulb Replacement Schedule
UVB bulbs lose output long before they stop producing visible light. A tube that looks perfectly bright may be putting out negligible UV after several months of use. Replace T5 bulbs every 12 months and T8 bulbs every 6 months. If you have a Solarmeter 6.5 UV Index meter, you can test output directly and replace only when levels drop below your target, but most keepers don’t own one. Sticking to the replacement schedule is the simpler path.