Do Tortoises Need UVB Light? (Yes — Here’s Why It’s Critical)

Proper lighting is one of the most important parts of tortoise care. UVB light helps tortoises produce vitamin D3, which allows their bodies to absorb calcium and build strong shells. This can be easily overlooked as special lighting is pretty specific to reptile keeping, but it is one of the most important pieces of equipment when keeping Tortoises.

Without UVB lighting or natural sunlight, tortoises can develop serious health issues.

Do Tortoises Need UVB Light?

• Yes tortoises need UVB light to stay healthy. There is no substitute or way around not having UVB lighting.

• UVB helps them produce vitamin D3, which allows their body to absorb calcium and maintain a strong shell and bones.

• Without UVB, tortoises can develop serious health problems like metabolic bone disease. No UVB overtime leads to many problems. Fully preventable with the right light bulbs.

A proper diet is also important to a tortoise health: Learn more:

What Do Tortoises Eat?

What Is UVB Light?

• UVB light is a type of ultraviolet radiation that reptiles use to produce vitamin D3. This light replicates the sun and the ultraviolet radiation the sun gives off everyday.
• In the wild, tortoises receive UVB exposure from natural sunlight while basking. The sun is the best source of UVB and tortoise have evolved to use UVB to produce Vitamin D3 which helps calcium consumption.

• Indoor tortoises require artificial UVB lighting to replicate this natural process. This lighting not only helps your tortoise stay healthy but with it you will notice your pet tortoise become more active and show more natural behavior.

Why UVB Is Important for Tortoises

UVB lighting helps tortoises:

• Absorb calcium– this is very important when it comes to tortoises as their shell and bone structure must be strong for protection and to structurally carry a heavy body.
• Grow strong shells– Strong solid shells are signs of a healthy tortoise. This is their protection and as adults it will be solid and hard to the touch.
• Maintain healthy bones– Healthy bones and skeletal structure is important because tortoises can become heavy. If you have a lot of weight to carry you need a good structure to hold it.
• Support proper metabolism– Metabolism and digestion is important and calcium plays a huge roll in all this.

Without UVB light, tortoises can develop metabolic bone disease, which causes severe skeletal problems. Metabolic bone disease happens over time and can easily be prevented with the right care and equipment and lighting.

What Happens If a Tortoise Doesn’t Get UVB?

• Soft shell (metabolic bone disease)- This happens over time and is caused by now UVB and lack of calcium.
• Weak bones- With the lack of calcium absorption weak bones can become a thing. usually start seeing nails curling.
• Lack of appetite- UVB is important to overall health and a lack of appetite is one of the first signs of something wrong.
• Lethargy- A little later sign of something is wrong is lethargy. Being weak or sleeping all the time or unactive is cause for concern.
• Poor growth- Tortoise should grow at a pretty steady pace and smooth. If the growth is slow, or stunted like this can be from no UVB and low calcium absorption. UVB is just as important as a proper diet, proper enclosure, and environment.

Learn more on why your tortoise might not be eating with this article: Why is My Tortoise Not Eating?

Indoor vs Outdoor Tortoises

• Outdoor tortoises typically receive enough UVB from direct sunlight. Tortoise by nature will bask to warm up throughout the day and this is where they natural will get their UVB intake.

• Indoor tortoises rely entirely on artificial lighting to meet their needs. They must have a UVB light or they will have no way to metabolize calcium and their bones and shell will start to get brittle or soft. It is important to have a working UVB light in your indoor enclosures.

• Proper UVB bulbs should be used alongside a basking heat lamp. I like to use florescent tube UVB bulbs as it covers more area and it creates a great amount of light over a the enclosure without putting off heat. A basking area is there to help warm the tortoise up, so they run hot. I like to have both lights on my indoor enclosers.

Do Outdoor Tortoises Need UVB Light?

• If fully outdoors- they have natural sunlight you will not need to provide a UVB light.
• If indoors partially or part time- Yes, they will need a UVB light. This is important even if they get partial sun or outdoor time each day.

Best UVB Lighting Setup

A proper lighting setup usually includes:

• UVB fluorescent bulb or tube– This is what I like to use for my tropical species, box turtle species and hatchlings. They put off a good strong UVB but not a ton of heat.
• basking heat lamp– These are separate from the UVB tube light and the ones I use are just giving off heat to allow my tortoises warm up when they want. You can get a MVB which is a heat bulb that also puts out UVB. These lights are very very hot and work better for desert species and bigger enclosures.
• appropriate basking temperature– Depending on the species you want a basking range of 90-100 degrees F. For my tropical species I like to go more in the range of low 90s. For my desert loving species I will go mid to high 90s.

The UVB bulb should be positioned above the tortoise enclosure so the animal receives consistent exposure while basking. Also be sure to have the lights on a timer or have a good schedule.

How to Provide UVB Light for a Tortoise

• Use reptile UVB bulbs- These are specifically made for reptiles to provide UVB for your pet. Tortoises are a type of reptile and these type of lights are needed when kept indoors.
• Place the UVB light 10-20 inches from the basking area. This is optimal distance and if you are unsure usually you will see a graph on the UVB bulb box to help pick the best distance.
• Replace the bulb- They don’t last forever. Even if the bulb is putting of light it does not mean its putting off UVB. Best rule is to replace the bulb every 6 months.
• 10-12 hour days is perfect. I keep all my UVB lights on 10 hrs. in the winter, and 12-14 hrs. in the summer.

How Long Should UVB Lights Stay On?

How Long Should UVB Lights Stay On?

For me I like to do about 10-12 hours of UVB lighting during the fall and winter months. During Spring and Summer I will keep UVB lights on for 13-14 hours. This will help replicate the seasons as well as give them a good day and night cycle.

Timers:

I also like to put my lights on timers. Timers are cheap and will help keep things very consistent for your pet tortoise. You can find digital ones, analog ones, and even WIFI timers. These are game changers and can help you with maintained when keep more then one tortoise or species at a time.

Replacing UVB Bulbs

• UVB bulbs lose strength over time. Depending on the manufacture they can last anywhere from 6-12+ months. I found some bulbs can last over a year but if you do not have a UVB meter I would just replace it based on time.

• Even if the bulb still produces light, UVB output decreases. This is something that most new reptiles don’t know. A florescent bulb will run for years and years but the UVB output will be 0 after a certain amount of time.

• Most bulbs should be replaced every: 6–12 months depending of manufacture. I like to replace mine every 6 months just to be safe, but I do have a UVB meter and have seen some lights put good amounts of UVB up to 12 months or more.
• UVB meter- This is a tool you can get that reads the UVB index. They work great if you keep a lot of reptiles indoor and overtime you can save money by using bulbs their whole life cycle. The tool is an expensive investment and not needed, but it does help.

FAQ Section

Conclusion

UVB lighting is essential for tortoise health, especially for animals kept indoors. By providing proper UVB exposure and a balanced diet with calcium, keepers can help their tortoises grow strong shells and maintain good health. When keeping your tortoise indoors UVB light is a must have no way around it. IT is best however to keep your tortoise outdoors when big enough or if all possible. Nothing beats natural sunlight and being outdoors.

What Next

If you’re new to tortoise keeping, start with our Beginner’s Guide to Tortoise Care before choosing your species.

• Full Care Guide → /care-guides/
• Diet & Nutrition → /diet/
• Habitat & Enclosures → /habitat/
• Gear Reviews → /gear-reviews/

Continue building your tortoise’s diet:

• Best Weeds for Tortoises to Eat
• Best Leafy Greens for Tortoises
• Best Vegetables for Tortoises
• Best Fruits for Tortoises