The Best UVB Bulbs for Tortoise in 2022

TheCritterCove is reader-supported. When you buy via links on our site, we may earn an affiliate commission at no cost to you. See more here.

best uvb light for tortoises

Getting to know why light is necessary for your pet tortoise and what UVA and UVB rays do for them, will make everything easier to understand when looking for the best UVB bulb.

The lights aren’t just so we can see them better when it’s dark but to help them grow healthy and maintain the right amount of nutrients in their day-to-day life.

When purchasing the best UVB light for a tortoise you will need to keep into consideration some factors that will decide the well-being of your tortoise.

Just as we need the sun to regulate our activities and help us with vitamin D synthesis, so also our reptile friends depend on sunlight.

Without the right amount of light and heat, your pet tortoise will have health issues ranging from minor to very serious ones.

With proper lighting and heating from the best UVB bulbs, you will have a healthy and happy pet.

Why is Light Important for Tortoises?

The primary point that we need to cover is that tortoises are reptiles and the importance of this is that all reptiles do something called thermoregulation.

Basically, we humans maintain our constant body temperature throughout the day, however, reptiles can only rely on outside light sources in order to raise or lower their body temperature.

Reptiles can raise their body temperature to increase metabolism or lower them to be more dormant and they can achieve this by moving to various areas of their surroundings to warm up or cool down.

These can be done through radiationconvection or by the evaporation of body fluids.

It may be either raised or lowered by the conduction of heat to or from the substratum or the air.


Conductive heat

Conductive heat is the transfer of heat within an object (such as down a long metal pole) or between two objects that are touching each other. 

The reptile sitting on a basking spot that has been warmed by the sun/heating element glowing on it, or from within in the case of a heating pad/rock.

Convective heat

Convective heat usually involves the movement of either air or water and the heat is carried via movement of this matter.

The warm air/water that blows/flows across the reptile.

Radiant heat

Radiant heat transfer involves the flow of thermal energy by electromagnetic waves. An example of radiation transfer is the reptile or amphibian basking in the sunlight.

The reptile absorbs the electromagnetic radiation from the sun/heat element.

The Best UVB Bulbs For Tortoise

amazon product

Top Pick

Zoo Med 2 Pack of T8 ReptiSun 10.0 UVB

If you click this link and make a purchase, we earn a commission at no additional cost to you.

The best uvb bulbs for tortoises are the tube UVB light bulbs and are a little bit more expensive but a little bit more powerful and they usually fit in your standard tortoise enclosure with them also being very safe to use for your turtle.

The UVB tubes are produced for reptile use and are often categorized according to their percentage UVB output. 

They are available offering from 2% UVB to 8% UVB output. 

The most popular tubes offer 3% or 5% UVB output. 

In the vast majority of cases the 3% tubes are perfectly adequate, granted they are correctly placed.

For a 3-5% UVB tube, 10-12 hours daily has shown a adequate level of exposure for most tortoise species. 

Concerns have been displayed about the safety of tubes with outputs greater than 5% where there may be a possibility of eye damage occurring with some tubes in some circumstances.

amazon product

Top Pick

Zoo Med ReptiSun 10.0 UVB Mini Compact Fluorescent (13 watts)

If you click this link and make a purchase, we earn a commission at no additional cost to you.

What is UVB Light and Why do Tortoises Need it?

The UVB light is a type of light that the sun releases and is part of the UV Spectrum. 

This UV Spectrum is broken up into 3 parts, these being the UVA, UVB and UVC lights and they can all be found in the direct sunlight.

The UVB light helps your tortoise get vitamin D3 which also absorbs calcium to build a hard shell and strong bones.

You can also expose your tortoise to a UVA light as this will help him regulate his behaviors such as feeding, daily movement, and mating.

These two types of ultraviolet lights perform different roles for your reptile pet and mixing them will ensure him a long-lasting life.

Lack of UVB Light Source

Enclosing your tortoise in an indoor shell and away from heat and any source of UVB will lead to a deficiency in vitamin D3.

This will affect its ability to metabolize calcium and results in metabolic bone disease.

Symptoms of metabolic bone disease are limping, bow legs, softening of the lower jaw with unusual flexibility, difficulty in raising body off the ground, lack of appetite and soft-shell.

Reduction in calcium levels may result in lethargy, tremors, twitches, weakness, seizures, depression and even death.

The Importance of UVA Light

vitamin D pathway

The pathway begins when a cholesterol, provitamin D, (7DHC) is manufactured by  the cells in the skin. When revealed to the UVB at wavelengths between 290 – 315nm, this provitamin D is converted very fast to previtamin D3.

Previtamin D3 is then isomerized (modified by a re-arrangement of atoms in the molecule) gradually, in warm skin over several hours to vitamin D3.

UVB is an acronym that stands for ultraviolet B-rays. Your tortoise needs UVB for the synthesis of vitamin D3 and this can be gotten naturally from the sun.

Heat is needed for the reaction to proceed at a normal rate.

Reptiles obtain this heat from the sun or any other heating source, as they bask.

The vitamin D3 is released from the skin cell membranes and is taken up by a “vitamin D-binding protein” into the plasma.

It is therefore carried in the bloodstream from the skin to the liver, where it is hydroxylated to calcediol, 25-hydroxy-vitamin D3.

This is the substance that is tested for in blood samples taken to assess the reptile’s vitamin D status.

amazon product

Top Pick

Zoo Med ReptiSun 5.0 UVB Mini Compact Fluorescent (13 watts)

If you click this link and make a purchase, we earn a commission at no additional cost to you.

Using UVB Light Bulb The Right Way

Lifespan of a Light Bulb

When using UVB bulbs for your pet, you have to bear in mind the fact that the bulbs deteriorate in their UVB output over time.

It is recommended that you change the bulb after 10 months or as recommended by the manufacturer.









10-12 MONTHS


The bulb may still produce lighting but it doesn’t mean that it still emits UVB, so distinguish between both functions.

Setting the Light Bulb in the Enclosure

There is a right way to use the bulb to get the best effects. Placing it with nothing but air standing between it and your tortoise ensures that no amount of UVB is absorbed.

UVB is not like x-rays or other forms of electromagnetic radiation that penetrates objects.

The UV light wavelengths are filtered by plastic and glass so when placing them in the habitat be sure they have direct exposure to the enclosure.

It gets absorbed and so your tortoise will still suffer from vitamin D deficiency if there is anything shielding the UVB from reaching it.

Also for the best effects, you do not have to exceed 10 to 15 inches above your tortoise when mounting the bulb except otherwise stated by the manufacturer. This way your tortoise gets the adequate amount it needs.

Placing the bulb too close can cause burns so you should avoid that.

When buying a UVB bulb, ensure to check the amount of UVB it delivers. This is so that you will purchase a bulb that meets the needs of your tortoise. Too low will not be beneficial and too high will be harmful.

Most species of tortoise, however, need about 4% of UVB.

There are bulbs that are made to provide heat, or light and also bulbs that are made to provide both.

All these are essential for your tortoise to be healthy so check out the features of the bulb you are about to buy and ensure it gives you what you want.

Daytime and Night Lights

The UVB bulbs are meant to mimic life in the open. So you cannot leave the bulb on for 24 hours. Light gives energy and marks the beginning of activities.

So when it is daytime, you put the UVB on so that your pet can stay awake and when it is night, you put it off so your pet can rest.

It is generally advisable to leave the bulb on for 12 hours of daytime and off for 12 hours of nighttime.

This means that if you are using one bulb as both heat, light and UVB source, you need to have another source of heat for your tortoise when the UVB light is off.

Common Questions About Tortoise UVB Lights

UVA or UVB for the tortoise?

Both are very essential to the health of your tortoise. UVA light helps regulate natural behaviors of your tortoise like feeding, mating, diurnal movement and others like this.

How long does a tortoise need a heat lamp?

A tortoise needs heat for 8 to 18 hours.

How long should a tortoise lamp be on?

You should turn it on for 12 hours signifying day time. When it is night, you have to turn it off so your pet tortoise can get some rest.

What is the right wattage of UVB bulb for a tortoise?

There is no specific wattage of UVB bulb for your tortoise. The wattage you choose should depend on the size of its habitat and temperature of the region. But ideally, 13, 75 and up to 200 watts will do just fine.


The use of UVB bulbs cannot be overemphasized if you really want your tortoise to be healthy and happy.

It is essential in its vitamin D synthesis and calcium metabolism so that your tortoise can make use of it to build strong bones and a hard shell.

The bulbs are a bit expensive but compared to their benefit, they are totally worth it. Lack of a source of UVB for your tortoise means death in the long run.