Bearded Dragon Lighting and Heating: UVB and Basking Explained

Bearded dragons need two kinds of light to stay healthy: a strong UVB lamp, so they can make vitamin D3 and use calcium properly, and a bright basking lamp that creates a hot spot at one end of the enclosure. Together these recreate the sunny, warm conditions of their native Australian habitat. Getting bearded dragon UVB lighting and heating right is one of the most important parts of their care, and one of the most common things to go wrong.

Key Points

• Bearded dragons need UVB every day. Without it they cannot use dietary calcium properly and can develop serious bone problems.
• A long linear UVB tube, such as a T5 high-output lamp, is the usual choice. Follow the lamp maker’s guidance on distance and replacement.
• Provide a temperature gradient: a hot basking spot at one end and a cooler area at the other, so your dragon can regulate its own temperature.
• Measure, do not guess. Use digital thermometers with probes, and an infrared thermometer for the basking surface.
• Glass and most plastics block UVB, so sunlight through a window does not count.

Why Bearded Dragons Need UVB

In the wild, bearded dragons spend much of the day in bright sunshine. Ultraviolet B light hitting the skin allows the body to make vitamin D3, which it needs to absorb and use calcium from food. Without enough UVB, the body draws calcium from the skeleton instead. Over time this can lead to metabolic bone disease, which causes weak, soft or deformed bones, tremors and difficulty moving.

UVB also appears to support normal behaviour, appetite and activity, and the bright light of a good setup helps dragons see their surroundings clearly. Reptiles see a wider range of light than we do, so a dim enclosure that looks fine to us may feel gloomy to them.

Choosing A UVB Lamp

For most adult bearded dragons, a linear T5 high-output UVB tube in a reflector is the standard recommendation. These lamps are labelled with a rating such as 10–14%, indicating a strong output suited to desert-dwelling species. Older-style T8 tubes are weaker and need to be much closer to the animal to be effective.

When choosing a lamp:

• Length: a tube covering roughly half to two-thirds of the enclosure length, positioned over the basking end, gives a UV gradient so your dragon can move in and out of it.
• Reflector: a reflector directs light downwards and noticeably increases the UVB reaching the animal.
• Brand guidance: output varies between makes. Reputable manufacturers publish recommended mounting distances and expected UV levels for their lamps. Use these rather than general rules of thumb.
• Avoid cheap compact coils and unbranded bulbs whose output is not clearly stated.

Mercury vapour lamps, which provide UVB and heat in one bulb, are another option, but they need careful placement and are usually best suited to large enclosures.

Distance, Mesh And UV Index

UVB weakens quickly with distance. If the lamp sits above a mesh lid, the mesh can block a substantial share of the output, so the dragon needs to be closer than it would with the lamp mounted inside the enclosure. Many keepers use the UV Index (UVI) as a guide. For bearded dragons, a commonly recommended UVI at the basking spot is somewhere in the region of 3 to 6, falling to near zero in shaded areas. A UV index meter is the most reliable way to check this, but if you do not have one, follow the manufacturer’s distance tables closely.

Provide shade and hiding places so your dragon can always get out of the UV zone. A gradient of light is just as important as a gradient of heat.

Heat And The Basking Spot

Bearded dragons are ectotherms, meaning they rely on their surroundings to warm up. They bask to raise their body temperature for digestion and activity, then move to cooler areas when they have had enough. Your job is to provide the full range.

The figures below are widely used husbandry ranges for adult bearded dragons. Individual needs vary, juveniles are often given a slightly warmer basking spot, and your vet may advise differently for a particular animal.

Area	Typical daytime range
Basking surface (measured on the surface itself)	About 38–42°C
Warm end air temperature	About 30–35°C
Cool end air temperature	About 24–29°C
Night-time	A drop to around 18–22°C is generally well tolerated

The basking lamp is usually a white halogen or similar visible-light heat bulb in a guarded fitting, aimed at a flat rock, slate or branch at the warm end. Visible light and heat from above mimic the sun far better than heat from below. Under-floor heat mats and heat rocks are not suitable as the main heat source and can cause burns, as dragons do not always sense heat from beneath well.

Thermostats And Thermometers

Every heat source should be controlled by a suitable thermostat. A dimming thermostat is the usual choice for basking lamps, as an on-off thermostat makes bulbs flicker and fail. Check that the thermostat you buy is rated for the type of heater you are using.

For monitoring, use a digital thermometer with a probe at each end of the enclosure, and an infrared temperature gun to check the basking surface directly. Stick-on dial thermometers are often inaccurate. Check readings at different times of day, especially when the season changes and your room gets warmer or colder.

Fit guards over bulbs and heaters, or position them outside the reach of your dragon, to prevent burns from direct contact.

Day Length And Night-Time

A consistent light cycle helps regulate behaviour, appetite and sleep. Many keepers provide around 12–14 hours of light in summer, sometimes reducing this slightly in winter. A simple plug-in timer controlling the UVB and basking lamps makes this easy.

At night, all lights should go off. Bearded dragons need darkness to sleep, and coloured “night” bulbs, whether red, blue or purple, can still disturb them. If your home gets cold enough that night temperatures fall well below the range above, a ceramic heat emitter or deep heat projector on a thermostat can provide heat without light.

Replacing UVB Lamps

UVB output declines over time, even though the lamp still looks bright to us. That is why a working bulb can stop doing its job without any visible sign. Manufacturers state how long their lamps remain effective; many T5 tubes are replaced around once a year, and some other types sooner. Write the installation date on the lamp or in a notebook, and replace on schedule. A UV meter lets you check output directly rather than relying on the calendar alone.

Common Lighting Mistakes

• Relying on a window: glass filters out almost all UVB, and direct sun through glass can overheat an enclosure quickly.
• Lamp too far away: especially through mesh, a weak or distant lamp may provide very little UVB at the basking spot.
• No gradient: a small enclosure heated evenly throughout leaves the dragon no way to cool down.
• Guessing temperatures: without thermometers, a basking spot can easily be far too hot or too cool.
• Forgetting replacements: an old UVB tube can leave a dragon without effective UV for months.

Lighting works alongside diet. A varied diet of suitable insects and leafy greens, with a calcium supplement used as advised by your vet or a reputable care guide, completes the picture.

When To Speak To A Vet

Problems related to lighting and heating often develop slowly. Speak to a vet experienced with reptiles if you notice:

• Twitching, tremors or a shaky walk
• Swollen, bent or rubbery-feeling limbs or jaw, or difficulty lifting the body off the ground
• Lethargy, poor appetite or weight loss that is not explained by seasonal slowing down
• Burns or blisters on the belly or back
• Gaping, wheezing or bubbles around the nostrils
• Long periods of inactivity with dark colouring and closed eyes during the day

Some bearded dragons naturally slow down for a few weeks in winter, a process called brumation, but because illness can look similar, it is wise to have a vet check before assuming this is the cause. This article is general guidance; always seek advice from a qualified veterinarian about your own animal.

Frequently Asked Questions

Can I Turn The UVB Lamp Off At Night?

Yes. UVB and basking lamps should run during the day only, usually on a timer, with complete darkness at night.

Is A UVB Bulb Enough To Heat The Enclosure?

Usually not. Most fluorescent UVB tubes give off very little heat, so a separate basking lamp is needed. Mercury vapour lamps are the exception, as they provide both.

Can My Bearded Dragon Go Outside For Natural Sunlight?

Supervised time in natural sunshine, in a secure enclosure with shade, can be beneficial in warm weather. Never leave a dragon in a glass tank or closed container in the sun, as it can overheat quickly.

How Do I Know If The Basking Spot Is The Right Temperature?

Measure the surface with an infrared thermometer. Behaviour helps too: a dragon that basks briefly, then moves away and returns later is usually comfortable.

Investing in good lighting and heating at the start saves a great deal of worry later. For more reptile guides, visit our reptile care hub, or browse the care library for advice on other pets.