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Metabolic Bone Disease in Turtles & Tortoises

While metabolic bone disease in turtles isn’t exactly a disease as its name implies, this disease causes a lot of harm among pet turtles and in severe cases, this complex disease can be a major killer of young turtles, highlighting the importance of proper husbandry.

Metabolic bone disease in turtles & tortoises refers to all conditions the softens and deforms the turtle’s shell and bone structure. It is also referred to as metabolic bone disorder and there are several types. 

The most common type is secondary nutritional hyperparathyroidism, a condition affecting calcium metabolism in the reptile’s body, which is caused by an unbalanced diet and lack of access to UVA/UVB light.

Other common types include renal secondary hyperparathyroidism, primary hyperparathyroidism (PHPT), fluorosis, osteoporosis, and rickets/osteomalacia.

Metabolic Bone Disease in Turtles & Tortoises

Nutritional Secondary Hyperparathyroidism

As already mentioned, nutritional secondary hyperparathyroidism (also nutritional metabolic bone disease) is the most common form of MBD. This type of metabolic bone disease can be easily corrected or prevented.

Regardless, it’s best to see a herp vet if you think your turtle or tortoise is suffering from MBD. A vet can properly diagnose your turtle and determine the type of metabolic bone disease your turtle is suffering from.

Nutritional metabolic bone disease is caused by one or more of the following – insufficient vitamin D3, insufficient calcium, and too much phosphorus.

It can also be exacerbated by poor humidity, temperature, and lighting. If your tortoise is pyramiding then it is generally down to NSHP (nutritional secondary hyperparathyroidism).


For pet reptile owners, especially those with red-eared sliders and other common reptile species, understanding the signs of metabolic bone disease is crucial. Long time neglect or poor diet can exacerbate these symptoms.

Before you can take action, you need to identify MBD. Since metabolic bone disease is linked to a lack of calcium, most of the symptoms are down to muscles, bone, and shell development.

Signs can differ slightly between freshwater turtles and tortoises as shell development differs between the two.

Shell deformity – Expect shell pyramiding in tortoises and soft shell development in turtles & tortoises as well. Due to the lack of calcium you can expect the shell to become soft and leathery.

A softened shell feels leathery and isn’t firm to touch.

Shell Pyramiding
Marginated tortoise being held by keeper showing pyramiding on the shell

The shells of tortoises may also become pyramid like. This phenomenon causes the scutes to develop into pyramids on the tortoise’s carapace.

It can be a rather unsightly look.  MBD isn’t to be confused with the soft shell of hatchlings.

Hatchlings have springy shells naturally but this doesn’t last past their first year. This isn’t a symptom of MBD. Similarly, softshell turtles have soft shells by nature.

Additional Issues

  • Deformed jaws
  • Deformed and/or weak limbs – Expect the turtle to drag the limbs as it walks.
  • Paralysis – In serious cases, poor shell development can affect the spine and lead to paralysis.
  • Cloacal/Penile prolapses – This is easy to spot as it looks similar to hemorrhoids.
  • Splayed out legs
  • Tiny shells
  • Beak deformity
Elongated Tortoise lost use of back legs due to MBD
Elongated Tortoise lost use of back legs due to MBD


Proper lighting, especially UVB lighting, is essential for normal vitamin D production, which aids in calcium metabolism. Natural sunlight or unfiltered sunlight, where feasible, provides beneficial ultraviolet light.

In captive reptiles, especially those kept indoors without access to natural sunlight, UVB bulbs or a mercury vapor bulb can be used to mimic natural conditions.

Nutritional secondary hyperparathyroidism is down to diet. If the meals fed to your turtle are low in calcium, it will lead to metabolic bone disease.

You have to feed turtles foods that are high in calcium. Examples of such food items are given in the section below titled – Feed Chelonians Foods Rich In Calcium. Also, vitamin D3 helps in the absorption of calcium.

As such, vitamin D3 deficiency can also lead to metabolic bone disease. Installing UVB lights and supplementing the turtle’s meal with calcium can help prevent vitamin D3 deficiency.

Exposure to sunlight also prevents vitamin D3 deficiency. However,  glass enclosures can heat up to dangerous levels when exposed to direct sunlight.

Lastly, too much phosphorus can lead to metabolic bone disease. A negative calcium-phosphorus ratio is deadly. Although phosphorus is an essential nutrient, it can also inhibit the absorption of calcium.

To prevent a negative calcium-phosphorus ratio feed turtles with foods high in calcium.

Here are some of the causes of MBD:

  • Calcium deficiency
  • Vitamin D deficiency
  • High levels of phosphorus in the turtle’s diet 
  • Inadequate exposure to UV light (UVB/UVA)
  • Intestinal disease
  • Liver/Kidney disease
  • Low enclosure temperatures.
  • Thyroid and parathyroid disorders

Management & Prevention

As a responsible turtle keeper there are several factors you need to pay close attention to in order to keep MBD in check. It’s a good idea for reptile and tortoise owners to focus on a nutritious diet, ensuring enough calcium and maintaining a proper phosphorous ratio.

As long as the living conditions of the turtle are right, metabolic bone disease can be prevented. That being said you should always keep an eye out for any odd growths or changes in the physiology of your turtle or tortoise.

You can track these changes by taking pictures and keeping a journal even and if an issue is discovered, consult your herp vet for help. Also, a care sheet can be a helpful tool for reptile owners to monitor their pet’s health over a long time.

In extreme cases, where turtles have been permanently affected by MBD, nutritional support and possibly fluid therapy are required for management.

Feed Chelonians Foods Rich In Calcium

As you may have already noticed, improper calcium to phosphorus ratio is one of the main causes of metabolic bone disease.

So, to make sure this doesn’t happen, you should feed your turtles and tortoises foods that are rich in calcium.

Some of these foods include collard greens, cabbage, bok choy, alfalfa, spinach, okra, cantaloupe, squash, berries, sprouts, and kale.

Tortoises, in particular, are mostly herbivorous and require a high fiber diet.

Some excellent foods for herbivorous tortoises include alfalfa, carrots, clover, collard greens, turnip greens, dandelion greens, mulberry leaves, mustard greens, opuntia cactus, radicchio, red leaf lettuce, romaine lettuce, rye, and bermudagrass.

For turtles that tend to be predominantly carnivorous such as softshell turtles, mud turtles, musk turtles, and other North American turtles, feed them whole fish such as tilapia/feeder fish, pinkie mice, shrimp, crustaceans, and raw lean beef. These aren’t the only suitable foods. Feeder insects, when included in the diet of species like baby turtles, should also be considered for their calcium-rich content.

As most turtles are omnivores, a mix of plants and animal protein is best. Hatchlings and juveniles tend to be more carnivorous while adults are more herbivorous.

Just make sure to properly research the dietary needs of the turtle. That way you know that you’re feeding it the right types of foods.

Supplement your turtles and tortoise diet with commercially produced turtle foods such as  ReptoMin Food Sticks, Zoo Med Natural Tortoise Food, and Mazuri Aquatic Turtle Diet.

Additionally, calcium supplementation is necessary for a healthy diet, especially in cases where dietary levels of calcium are insufficient. Vitamin D supplements can help ensure that the chelonian acquires the needed amount of calcium and vitamin D3.

However, it is important that you don’t overuse these supplements as this can lead to medical complications.

Provide Chelonians With UV light

Turtles and tortoises alike need UV light to produce vitamin D naturally. Vitamin D in turn ensures that dietary calcium is optimally utilized by the chelonian.

The best source of UV light is sunlight. For turtles and tortoises housed outside, a daily dose of sunlight is more than enough. Turtles housed in glass/transparent PVC enclosures should not be exposed to direct sunlight as sunlight can quickly heat up the enclosure to dangerous levels. 

To ensure that even turtles housed in aquariums and terrariums are exposed to adequate levels of UVB light, install UVB light lamps such as a standard bulb with fixture Reptisun 10.0 bulb or the other fluorescent style T5 HO lamp.

Mercury vapor lamps also work well. However, keep in mind that they produce a lot of heat. Both the Tekizoo UVA/UVB Sun Lamp and the Zoo Med PowerSun UV Bulb are excellent heat-producing UV bulbs.

Keep Humidity Levels High For Tortoises And Turtles That Do Not Live In An Aquarium Or Pond

While the primary cause of MBD isn’t low humidity, they can worsen the situation and in some cases could trigger MBD.

In order to prevent this from happening, you should keep humidity between 60 & 80% at all times even for box turtles and tortoises that are endemic to arid ecosystems.

Of course, the humidity needs differ from one chelonian to another. For instance, ornate box turtles thrive in humidity levels of 80 percent, while greek tortoises and other Mediterranean tortoises can do with humidity levels of about 60 percent.

Make sure to do your research for your specific species to ensure you get the humidity levels right.

Here are some tips that will help you keep your chelonian in a humid environment.

  • Use a reptile humidifier for the enclosure or mist the enclosure manually or using a system to increase humidity levels.
  • Soak the chelonian in water for about 20 minutes every other day. Make sure the water isn’t overly high in order to prevent drowning your chelonian.
  • Get a digital hygrometer. This will allow you to keep track of the humidity of the enclosure. That way you can correct it when needed.
  • Make use of humidity retaining substrate such as Coconut Fiber to ensure the enclosure retains as much humidity as possible.
  • Provide a humidity box.
  • Provide a shallow bowl/pan of water that the tortoise can soak in without drowning.

Examples Of MBD (Video)

The below video highlights 3 different species of reptile including a yellow bellied slider and just how seriously this issue can affect the animals overall life.

You will notice that turtle is so misshapen that it can’t even walk properly and it’s shell is even high domed whereas normally it would be flat and smooth.


In conclusion, the treatment of MBD in turtles involves a holistic approach. This includes dietary improvements, ensuring proper diet, and maintaining a suitable environment. Regular check-ups with a vet, especially in cases of clinical signs like rubber jaw or shell rot, are vital for the health of your pet reptile.

It’s important to seek help from a qualified vet if you think your turtle is suffering from MBD.

This is because the different types of MBD require different treatments. The most common metabolic bone disease in turtles & tortoises, which is nutritional metabolic bone disease also known as nutritional secondary hyperparathyroidism, is easily preventable.

Just make sure that the turtle’s enclosure conditions (such as UV light exposure & humidity levels) are right, and that the turtle/tortoise is fed a well-balanced diet.

Although chelonians are hardier than other animals kept as pets, they are still vulnerable to health issues with the most common issue being metabolic bone disease.

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