Bearded Dragon UVB Light: T5 HO Setup, UVI, and Replacement Schedule

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A bearded dragon UVB light is not optional equipment. It drives the vitamin D3 synthesis that lets a dragon absorb calcium from its diet.

A missing, weak, or badly placed bearded dragon UVB light can undo a perfect diet. The result is metabolic bone disease.

This guide covers UVB only. It walks through bulb type, UV Index targets, distance, mesh loss, tube length, photoperiod, and replacement timing. For heat bulbs and the rest of the setup, see the bearded dragon lighting guide.

Why Bearded Dragons Need UVB Light

Wild bearded dragons live across deserts, dry forests, and scrublands in central and eastern Australia. They spend much of the day basking on branches, rocks, and fence posts in open sun.

That sunlight supplies the ultraviolet B wavelengths that skin uses to make vitamin D3. The MSD Veterinary Manual puts the useful band at 283 to 304 nanometers.

Vitamin D3 controls how much calcium a dragon can absorb from food. A dragon kept under ordinary room lighting gets almost no usable UVB, no matter how bright the room looks. Window light does not help either, because the RSPCA notes that UVB does not pass through glass.

A dedicated UVB light replaces that missing sun exposure. Skipping it, or running it wrong, is one of the fastest paths to metabolic bone disease.

T5 HO Tubes Are the Standard Choice

Three bulb formats show up in the reptile trade. These are compact coil bulbs, mercury vapor bulbs, and T5 high output linear tubes, usually called T5 HO.

Coil bulbs put out UVB in a narrow, uneven cone. Mercury vapor bulbs lock heat and UVB into one spot.

A T5 HO tube spreads UVB evenly along its length. It also lets you run heat and UVB from separate fixtures.

The RSPCA specifies a high output 10 to 12 percent tube, and Reptiles and Research recommends T5 HO desert tubes with a reflector. Most current bearded dragon UVB light setups use a T5 HO tube in the 10 to 14 percent range.

UC Davis sets a lower floor: no less than 5 percent UVB within 12 inches of the basking site. Treat that as the minimum for an older T8 fixture, not the goal. A 5 percent T8 tube rarely reaches a desert basking UV Index at a safe distance.

UV Index Targets and Ferguson Zones

UV Index, or UVI, measures how strong the UVB is at a given spot. It is the same scale weather reports use for sunburn risk. Bearded dragons sit in a high sun exposure group among reptiles.

The UV Tool, published in the Journal of Zoo and Aquarium Research, assigns Pogona vitticeps to Ferguson zones 3 to 4. Those zones cover a daytime UVI of 1 to 3.5 and a basking maximum of 2.9 to 9.5.

For these zones the authors recommend the sunbeam method. That means a basking area at UVI 3 to 5, like mid morning sun, and shade at zero.

The RSPCA gives the same basking figure of 3 to 5. Reptiles and Research targets a UVI of 4.

A gradient matters as much as the peak. It lets a dragon move toward or away from UVB the way it would adjust basking time outdoors.

Distance, Mesh, and Tube Length

UVB output falls off quickly with distance. The percentage on the box only tells you the output at the tube surface, not at the dragon. Reptiles and Research places the basking surface 30 centimeters, or 12 inches, below a reflected T5 HO desert tube.

Mesh matters. Reptiles and Research measured roughly a 30 percent loss through a standard screen lid.

The UV Tool authors advise the widest mesh possible. A tube mounted inside the enclosure needs more distance than the same tube on top of the screen.

Treat these distances as starting points drawn from manufacturer charts, not fixed rules. Tube age, reflector design, and mesh gauge all shift the real number, which is why a meter reading matters.

The tube should span one third to one half of the enclosure length, placed over the basking end. That gives full coverage where the dragon basks and leaves the other half in shade. A tube that covers the whole tank removes the zero UVB retreat the species needs.

Photoperiod: How Many Hours a Day

Run the UVB tube on the same timer as the basking lamp. The RSPCA uses 12 hours on and 12 off.

UC Davis suggests about 14 hours of daylight and 10 of darkness. Either works, and many keepers run 14 hours in summer and 12 in winter to mimic the seasons.

Switch everything off at night. UVB has no benefit in the dark, and constant light disrupts sleep.

Bearded dragons bask in the first hours after lights on. A morning feeding under full UVB fits that rhythm.

How Long a UVB Bulb Lasts

A UVB tube can glow white long after its real UVB output has dropped. Visible light and UVB fade on different timelines.

A tube that still lights the tank may no longer be doing its job. This is the single most common UVB mistake.

Authorities differ here. UC Davis says every 3 to 6 months and NC State says every 6 months. The MSD Veterinary Manual says once a year.

The vet school figures reflect T8 and compact bulbs, which lose output fast. Manufacturer data for T5 HO tubes supports 12 months. Mark the install date and use the shorter interval for anything that is not a T5 HO.

Measuring UVB Instead of Guessing

Distance charts and package percentages are estimates. The only way to know the actual UVI a dragon basks under is to measure it.

Hold a UV Index meter at the basking spot with the sensor facing the tube. A meter belongs in every reptile UVB lighting kit.

A meter reading catches problems a chart cannot. It flags an aged tube, a slipped reflector, or mesh that blocks more than expected. Check new tubes at install, then every two or three months.

UVB and Metabolic Bone Disease

Metabolic bone disease, or MBD, is one of the most common conditions seen in pet bearded dragons, and how long a dragon can go without UVB matters. It develops when a dragon cannot absorb or use enough calcium relative to phosphorus.

Feeder insects are high in phosphorus and low in calcium. The dragon depends on calcium dusting and on UVB driven vitamin D3 to close the gap.

The MSD Veterinary Manual notes that dietary vitamin D matters only when the animal cannot make its own. A weak tube creates exactly that situation. Distant, aged, or heavily blocked UVB leaves a dragon short on vitamin D3 even on a well supplemented diet.

Early signs include softened jaw bones, swollen limbs, tremors, and reluctance to move normally. A dragon showing any of these signs needs a reptile experienced veterinarian promptly. MBD can progress quickly once symptoms appear.

Morphs That May Need Less UVB

Some color and pattern morphs, including translucent, hypomelanistic, and scaleless dragons, have reduced pigment or scale coverage. No published study sets a separate UVI for them.

Keeper practice is to aim for the low end of the basking range, around 3. Watch for squinting or eye irritation.

Common UVB Mistakes

The most frequent error is letting a tube run well past its replacement date. It still produces visible light, so the mistake goes unnoticed until the dragon shows signs of MBD.

A close second is mounting a tube on a mesh lid at the distance meant for an open fixture. That can cut the basking UVI by a third or more.

Other mistakes are easy to list. A tube far shorter than one third of the tank.

A compact bulb placed inches from the dragon to make up for its narrow beam. A tank by a window on the theory that sunlight through glass counts, which it does not.

Recommended Bearded Dragon UVB Lights

The setups below cover both starting from scratch and replacing an aging tube. Every option below is a T5 HO desert strength bulb or fixture, matched to the UV Index targets and Ferguson zoning covered above rather than a generic percentage on the box.

01 · Best overall kitT5 HO UVB kit

Arcadia ProT5 Kit Desert 12%

Best for a first full desert UVB setup

• 12% desert output tube plus matched reflector
• Mount above open mesh, not glass or plastic
• Target UVI 3.0 to 6.0 at the basking spot

Why we pick it

• Fixture and tube are sold as a matched pair, so the reflector data behind the UVI targets above actually applies
• Desert strength suits open basking setups without extra shading

Keep in mind

• Measure with a UV index meter before trusting the label percentage

Check price on AmazonMount over mesh only, never behind glass

02 · Best replacement tubeT5 HO UVB tube

Zoo Med ReptiSun T5 HO 10.0

Best for swapping an existing fixture on schedule

• 10.0 desert strength T5 HO tube
• Fits standard T5 HO fixtures and hoods
• Replace on a fixed schedule, not by eye

Why we pick it

• Common desert strength that pairs with most existing T5 HO fixtures without a new hood

Keep in mind

• Replace annually even though the tube still lights up, since UVB output drops well before visible light does

Check price on AmazonLog the install date on the fixture

03 · Best upgrade fixtureUVB fixture

Arcadia ProT5 Fixture

Best for raising usable UVI from a tube you already own

• High output reflector housing for T5 HO tubes
• Works with desert or forest strength tubes
• Meaningfully raises usable UVI at the same distance

Why we pick it

• A documented reflector design gets more usable UVB to the basking spot from the same tube, instead of wasting light sideways

Keep in mind

• Skip off brand fixtures with no published reflector data, since UVI targets assume a known reflector

Check price on AmazonRecheck UVI after swapping fixtures

04 · Best budget fixtureUVB fixture

Zoo Med T5 HO Terrarium Hood

Best for a working setup on a tighter budget

• Standard T5 HO hood and reflector
• Fits common terrarium widths
• Lower reflector efficiency than premium hoods

Why we pick it

• A functional, affordable way to run a T5 HO desert tube while still hitting basking zone UVI with correct distance

Keep in mind

• Expect somewhat lower usable UVI at the same distance, so measure and mount closer if needed within the target range

Check price on AmazonMeasure UVI before finalizing distance

For a full desert basking setup including heat, see our bearded dragon heat lamp picks.

Frequently Asked Questions

What percentage UVB bulb does a bearded dragon need?

A 10 to 14 percent T5 HO tube is the standard. The RSPCA specifies 10 to 12 percent high output. The percentage only matters together with distance, mesh, and reflector, so the real target is a basking UV Index of 3 to 5.

How far should a UVB bulb be from the basking spot?

About 12 inches for a T5 HO desert tube on a mesh lid. Inside the enclosure, with no mesh, 15 to 20 inches. Confirm with a UV Index meter, since tube age and mesh gauge change the number.

What UV Index does a bearded dragon need?

The UV Tool places bearded dragons in Ferguson zones 3 to 4. It recommends a basking area at UVI 3 to 5 with shade at zero, and the RSPCA gives the same range.

Can a compact UVB bulb replace a T5 HO tube?

Only as a stopgap. A compact bulb throws a narrow cone that cannot cover a basking dragon evenly.

It also loses output within about six months. A T5 HO tube spreads usable UVB along the whole basking zone.

How often should a bearded dragon UVB light be replaced?

Every 6 months for compact and T8 bulbs. Every 12 months for a T5 HO tube, which matches MSD’s once a year guidance.

UC Davis advises 3 to 6 months, which is safest for older bulb types. A UV Index meter settles the question for any specific tube.

Can too much UVB hurt a bearded dragon?

Yes. A tube mounted too close, or a compact bulb inches from the head, can irritate the eyes and skin. Keep the basking UVI under about 5.0 and always leave a shaded area that reads zero.