Box Turtle Health Issues: Metabolic Bone Disease (MBD)


Turtle with deformed shell, possibly due to metabolic bone disease

A turtle with a deformed shell
Modified version of photo by popofatticus @ Flickr; licensed under CC BY 2.0

Metabolic bone disease (MBD) is a group of conditions that can develop when your box turtle doesn’t get enough calcium or can’t use the calcium in her diet.

It can affect your pet’s bones, shell, beak and nails. It also affects the internal organs, although you won’t be able to actually see these effects. This internal damage can shorten your pet’s lifespan.

Recognizing MBD

Unfortunately, by the time you see symptoms of Metbolic Bone Disease, it’s usually pretty advanced.

You may see symptoms like:

  • A soft shell (it deforms when you press on it or pick up the turtle)
  • Your pet has trouble walking and may even drag her hind legs
  • Her legs are splayed
  • The shell may grow curved upward on the edges
  • The scutes may start to look raised, giving them a bumpy appearance or feel (this is called pyramiding).
  • The hinge may not work (your pet can’t shut herself completely in her shell)
  • Nails may curve outward
  • Beak may grow to look like a duck’s bill

Deformed shell growth is especially common in young turtles with MBD because they are growing more quickly than adults.

The Turtle Rescue of Long Island’s website has a few rescue stories showing MBD. Eastern box turtle Scooter came to them with horrible symptoms. This ornate box turtle didn’t have the same degree of shell problems, but was still looking pretty sad when he showed up.

Another example of a sadly neglected boxie is this guy at All Wildlife Rescue and Education.

If you see any of these things, it’s a good idea to take your pet to your vet to confirm the diagnosis and evaluate how bad it is.

What Causes Metabolic Bone Disease?

There are a few things that can cause this problem in your boxie. Often it’s a combination of things:

  • Diet without enough calcium
  • Diet with enough calcium, but the wrong ratio of calcium and phosphorus
  • Not enough Vitamin D in the diet (without this, your pet can’t use the calcium)
  • Not enough UVB rays (these help her make Vitamin D on her own)

Now, a lack of UVB doesn’t have to cause MBD, if you make sure your pet gets enough calcium and Vitamin D in the diet (although using UV light is easier). But if you don’t feed enough calcium, no amount of either Vitamin D or UVB will prevent MBD.

The calcium to phosphorus ratio is important because your boxie’s body will try to maintain a ratio of about 2:1 (2 molecules of calcium for every one of phosphorus) in its bloodstream. If this ratio gets too far off, the body will start pulling calcium from the bones, making them soft.

Can You Reverse Metabolic Bone Disease?

Yes and no.

You can reverse symptoms like soft shell and bones. But if the shell is already deformed, it will always be deformed. The best you can do is stop it from getting worse. Damage to internal organs may also never heal completely.

To help your pet’s body rebuild bones and shell:

Give him plenty of UVB exposure, either by letting him spend time outside, or by setting up indoor UV lighting. You can choose from a few different kinds of bulbs. For example, a tube lamp like the Reptisun 5.0 UVB lamp supplies UVB to a large area of the habitat. And something like the PowerSun UV (a mercury vapor bulb) supplies light and heat along with UVB to a small basking area.

Add a calcium supplement to his diet. Use one without added phosphorus. Sprinkle it lightly on his food at every feeding.

Calcium comes both with and without added Vitamin D. You may want to get one bottle of each. Then use calcium with Vitamin D once or twice a week. Use the calcium without Vitamin D the rest of the time. As important as Vitamin D is for your box turtle’s health, too much can also be harmful.

Your vet can give you much more specific instruction, based on his or her examination of your pet’s condition.

Preventing Metabolic Bone Disease

Because this condition can be so disfiguring, and it can shorten your pet’s life even if it doesn’t cause serious shell problems, it’s best to prevent it in the first place.

Box turtle eating strawberryYou can prevent it the same way you treat it. Make sure your boxie gets enough calcium and Vitamin D, along with UVB exposure, as discussed above. The only difference might be that as long as he gets enough UVB, you shouldn’t need the calcium with Vitamin D.


4 thoughts on “Box Turtle Health Issues: Metabolic Bone Disease (MBD)

  1. j yudell

    My boxie has a white area around his mouth which is not soft or flaky. He lives in an enclosure outdoors. Almost everyday he lies in his water upside down for hours, but when I flip him around, he gets out of the water. I have had him since he hatched, about 15 years ago. I have other boxies in other enclosures who do not have the white beak or the upside down in-the- water behavior. I feed them all fruit/vegetable scraps twice a week and freeze-dried meal worms once a week.
    Thanks for any advice.

    1. boxturtleworld Post author

      I’m not a vet, so I can’t give you specific advice. Plus I’ve just never seen that. The only thing I can think about with the water is did you put in a new water bowl recently? Maybe one with higher or steeper sides? Maybe he’s falling backwards trying to get out (maybe he’s smaller than the others) and can’t get back up by himself? Although if he gets out ok after you put him right-side up, maybe not.

      As for the white area around his mouth, the first thing that comes to mind is mouth rot, which can be caused by a lot of different infections. It can look different depending on what causes it. Personally, I think I’d bring him to a vet to get checked out. If both the white mouth and upside-down behavior are new, I’d say it’s best to let a professional take a look.

      1. boxturtleworld Post author

        Yes, thanks Kait. My research has actually suggested more like 50% protein, 40% fruits/veggies, and 10% fungus (mushrooms). But definitely at least equal protein & plant foods.

        But two fruit/veggie meals and one mealworm meal could still be ok. It depends on much of each they eat at each meal. If each fruit/veggie meal is about 1/2 of the one mealworm meal, the total amounts each week would still be about equal. Does that make sense?


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