How Long Can a Turtle Go Without a UVB Light?

Like most turtle owners, you probably have a UV light installed for your pet so that it can regularly soak up the heat and UVB rays. But you may be wondering if it’s really necessary, or if you can go a few days without one until you have time to buy a replacement.

So how long can a turtle go without a UVB light? There’s not a solid answer to this question; in the turtle owner community, many say that you should never go without it. However, another group of turtle owners claims that UVB light isn’t truly necessary.

In this article, we’ll talk about the benefits of UVB light as well as arguments in favor of and against it. We’ll also discuss the possibility of metabolic bone disease, its symptoms, and its treatment.

What Benefits Does UVB Light Provide for Turtles?

As a turtle owner, you’re responsible for imitating your pet’s natural environment in the wild. A big part of that is providing a high-quality heat and UV light source, which acts as the sun would in nature. 

There are three main reasons that turtles need access to UVB light: to warm up their body temperature, to dry off their shell and skin after being in the water, and to soak up the UV rays, which contain Vitamin D3 and help them process calcium.

Warming up Their Body Temperature

Turtles are cold-blooded, so they rely on their environment to help them regulate their body temperature. This means that turtles will go back and forth between warmer and cooler environments periodically in order to thermoregulate.

In their natural habitat, turtles would bask under the sun’s rays or retreat into the shade to cool down. In captivity, it’s essential to give them the same options.

You’ll see turtles spending time in the dry, warm basking area of their aquarium on a daily basis. It’s important for turtles to soak up the heat from the UV light regularly, because it also acts to kill off bacteria by keeping the immune system working properly.

Drying Out Their Skin and Shell

Since many turtles spend a lot of time in the water, it’s extremely important that they have the opportunity to bask and completely dry off. When a turtle stays in the water for long periods of time, it’s very easy for fungi and bacteria to build up on its skin and shell. Basking in the warm UV light is a great way to combat this.

This light also regulates your turtle’s circadian rhythms, or day and night cycle. Remember, it’s your job to mimic your pet’s natural environment, and this includes creating a consistent day and night pattern! It’s recommended to turn on your UV light when the sun comes up and off when the sun goes down, or to turn it on for 12 hours and off for 12 hours. 

Soaking up the UV Rays

Although UVB rays typically get the most attention in turtle care articles, UVA rays are actually just as important. These two types of UV rays are responsible for multiple different functions in your turtle’s system.

  • UVA rays help to regulate your turtle’s mood, activity level, and metabolism. They also help maintain healthy mating and breeding activities.
  • UVB rays provide Vitamin D3, which is essential for processing calcium. Calcium in turn is responsible for bone and shell health, as well as growth and development.

UV Light Safety Tips 

First, it’s important to note that UV lights lose their effectiveness after six months to a year, so plan on replacing your bulb on a regular basis. Also remember that sitting your turtle by a sunny window won’t provide it with any UVB rays, although it may generate some heat.

When the rays pass through the window, the UVB rays are filtered out, so your pet won’t be getting the Vitamin D3 that it needs.

Hang your UV light about 12 to 15 inches above your turtle, and make sure there’s no chance of it falling in your turtle’s water–you don’t want your pet to get electrocuted! You’ll also want to ensure that you never look directly at the UV light because it can cause blindness.

What’s the Longest a Turtle Can Go Without UVB Light?

There’s a bit of controversy regarding the answer to this question. While many turtle owners agree that it’s not a good idea to go without a UVB light for any period of time, there’s also a large group of owners that claims it’s not necessary as long as your turtle’s diet includes the right amount of Vitamin D3.

Arguments in Favor of UVB Light

The three reasons above (thermoregulation, drying off from the water, and UV rays) make up much of the argument in favor of the use of UV lights. While it is possible to feed your turtle Vitamin D3 so that it can successfully process calcium, there’s a sizable risk of overdose.

UVB rays provide the perfect amount of Vitamin D3 for your pet with zero chance of overdose, so a UV light is considered the safer option.

The argument not to use UV lights also neglects the importance of UVA rays, which are very important for mood, metabolism, and breeding. It also doesn’t mimic a turtle’s natural environment in the way that is recommended, by using a UV light as an artificial sun for your pet.

Those who recommend using UVB light advise against leaving your turtle without it for any longer that you have to. While a day or two without UVB rays may not have any negative effect on your turtle, it’s possible that a prolonged period without it can lead to issues with the bones and shell, as well as growth and development. 

The most common illness that occurs in turtles that aren’t able to process calcium (which UVB rays enable them to do) is metabolic bone disease, which is life-threatening and must be treated by a veterinarian.

Arguments Against UVB Light

There are quite a few turtle owners who claim that it’s really not necessary to have a UV light. As long as a turtle has the correct amount of Vitamin D3 in its diet, it will be able to process calcium efficiently, preventing metabolic bone disease and other issues with growth and development. 

Does My Turtle Really Need UVB Light?

Overall, it’s up to your discretion whether you choose to use a UV light or not. However, a lack of UVB rays paired with a lack of Vitamin D3 is sure to lead to developmental issues and softening of the shell. Metabolic bone disease is expected to develop after a period of time without Vitamin D3 to efficiently process the calcium your turtle takes in through its diet. 

What Health Conditions Can Occur if My Turtle Doesn’t Get Enough UVB Light?

There are a few different issues that commonly take place when turtles don’t get enough UVB rays or the right amount of Vitamin D3 supplements.

Metabolic Bone Disease

Metabolic bone disease is a very serious illness that can be life-threatening for turtles. It’s a result of having too much calcium in the system that cannot be processed successfully. Some of the first signs of metabolic bone disease include:

  • Beginning to move differently than usual when walking and swimming
  • Struggling to climb out of the water
  • General appearance of weakness
  • Tremors

As the disease continues, the symptoms worsen. In advanced cases of metabolic bone disease, you may see:

  • A floppy jaw
  • Refusal to eat
  • Constipation
  • Bowed legs
  • Trouble raising itself off the ground
  • Marks on the bottom of the shell from dragging on the floor
  • Hard lumps along the spine and jaw

Treatment for Metabolic Bone Disease

As with most illnesses, the best treatment is actually prevention. It’s best to keep your turtle from ever getting metabolic bone disease in the first place by providing regular access to UVB rays or a Vitamin D3 supplement. 

Typically, a veterinarian will recommend that you install a UV light and begin creating a regular day and night cycle for your turtle. Oftentimes this helps turtles to get healthier pretty quickly, but they may still have lasting damage from the illness.

In some cases, your veterinarian will give calcium injections or prescribe various supplements for your turtle as well. Fluid therapy and nutritional support are given in severe cases. If any bones are broken as a result of metabolic bone disease, splints may be necessary for them to heal correctly.

While there’s a good chance that your turtle will recover if you catch metabolic bone disease early enough, it’s best not to risk it in the first place by providing your pet with the nutrients it needs to stay healthy.


UV light provides some great health benefits for your pet: heat for thermoregulation, light that mimics the sun and dries your turtle’s body after swimming, and UVA and UVB rays, which aid in all sorts of bodily functions. However, it is possible to provide your turtle with a Vitamin D3 supplement that eliminates the need for UVB rays. 

Without Vitamin D3, unprocessed calcium can build up in your turtle’s body and cause an illness called metabolic bone disease. This disease, although very serious, can be treatable–but make sure to get your pet to the vet if you think it’s suffering from metabolic bone disease!


I’m Devin Nunn, an average joe that just so happens to have a deep love and passion for everything to do with reptiles. Because taking care of them for the vast majority of my life wasn’t fulfilling enough, I decided to begin educating others about them through my articles. read more...