Metabolic bone disease (MBD) is a spectrum of disorders related to a lack (or imbalance) of calcium in the body. The bioavailability of calcium is determined not just by overall calcium in the diet but also by the interaction of other vitamins & minerals – most notably vitamin D3 and phosphorus. When the right balance is not available in the diet, calcium is pulled from its usual storage – bone mass.
What is MBD in crested geckos?
MBD in crested geckos generally takes the form of disfigured bones, especially in the spine, hips and tail. Weak jawbones are also a sign of MBD, as are swollen limbs. Trembling and overall ill health are caused by the internal turmoil the lack of calcium produces in the body: lack of muscle contractions, loss of liver and kidney function, a decrease of nerve function and problems in blood clotting.
If a calcium deficiency is not corrected through proper diet or syringe feeding, the gecko will die. Calcium is needed for proper muscle and organ function; the healthy level of calcium in the bloodstream is roughly 1%. Over-supplementation with calcium is rare but possible.
Providing a balanced diet is crucial to prevent this crippling disease.
Signs of MBD
- Swollen limbs (“Popeye” arms)
- Swollen jaw
- A weak jaw that hangs open
- Underbite or overbite
- Humped back
- Irregular spine
- Kinked tail with multiple zig-zags, especially combined with a humped back
- Shaking, trembling, or twitching of the entire body or extremities
- Organ failure
- Inability to eat
Look for signs in combination with each other, as taken individually they could be symptoms of something else, such as an injury, infection, or neurological or genetic condition.
Note that while a crested gecko suffering from MBD can be brought back to health, any deformities in the bone are permanent. Prevention is the best way to avoid crested gecko MBD!
According to a reptile vet, Dr Sadaar:
The first thing that I notice is a crooked tail, or weakness or tremors,” says John Makaryshyn, a reptile hobbyist and breeder. “You pick them up [and they’re] just shaky when moving around.”
He adds that he often hears owners describe their pet’s condition as “lethargic” or “wasting away.”
MBD occurs when there’s an improper balance of vitamins, minerals, and nutrients making up the reptile’s bones. Key factors are too much phosphorous, and low calcium and low vitamin D3 which regulate calcium absorption.
“If there’s not enough calcium in the bones, the bones are not as strong as they should be … sometimes the muscles can actually be stronger than the bones — depending on how much calcium is missing,” says Dr. Miranda Sadar, a former faculty member at the Western College of Veterinary Medicine (WCVM).
The board-certified specialist is now an assistant professor at Colorado State University’s Avian, Exotic, and Zoological Medicine Service.
“Of course with weak bones, they are more prone to getting fractures so a classic presentation of metabolic bone disease is going to be fractures.”
Sadar finds that juvenile reptiles are the most likely suspects for MBD, and sometimes, it takes owners a long time – two to three months after purchasing their pets – to visit a veterinarian.
“[That’s] often when we will start having animals come in for any kind of problem – [it] could be metabolic bone disease, it could be just straight anorexia,” says Sadar. “But those clinical signs may have been going on longer.”
Makyryshyn rarely has issues with MBD but finds breeding females the most challenging to prevent the disease since their eggs contain a lot of calcium. He notices the most problems with MBD during the spring when females begin laying their eggs.
In many reptile species, vitamin D3 is produced by the skin after sunlight exposure, which is replicated in captivity with ultraviolet (UVB) lighting. As well, some reptile species such as ball pythons can get adequate vitamin D3 from their diet.
Makaryshyn is frustrated by the lack of scientific information available for reptile owners and breeders – especially about topics such as UVB lighting.
“[For] some reptiles it’s debatable whether they need UV [light] or not. It would be nice to have some scientific data or even a vet who actually has experience with this [topic],” says Makaryshyn, who has owned over 20 different reptile species.
While care of reptiles and other zoological companion animals (exotics) is well established in Doctor of Veterinary Medicine (DVM) programs at veterinary colleges like the WCVM, Sadar agrees that the lack of scientific data in the area is challenging for owners. As an exotic animal veterinarian, she prefers owners to err on the side of caution and provide UVB lighting for their reptile pets. UVB bulbs also degrade over time, so timely bulb replacement is important.
“Once they started to actually do emission studies … we’re realizing that six months [between bulb replacement] may even be stretching it. Some people may go as short as four months, so we say every four to six months,” says Sadar. “We typically tell people that it [UVB] doesn’t penetrate glass and plastic so don’t put those between the light and the reptile.”
If a lack of UVB lighting isn’t the problem, insufficient calcium in a reptile pet’s diet is another common cause of MBD. Many feeder insects, such as crickets, are high in phosphorous and low in calcium. To compensate, Makaryshyn dusts his reptiles’ meals – crickets and fruit flies – with calcium and vitamin D3 if certain pets don’t have access to UV lighting.
According to Sadar, reptile owners can run into problems if they feed too many live crickets at once. This allows the insects enough time to groom the calcium dust off before being eaten.
However, Sadar warns that it’s possible for reptile owners “to overdo it” with vitamin D3 supplements, which could potentially damage the reptile’s kidneys.
“The worst-case scenario is if you have a reptile that can absorb vitamin D from the sun and can also absorb vitamin D from the diet,” says Sadar. She adds that doubling up on vitamin D supplementation could potentially cause toxicosis in the pet.
Sadar notes that the success rate for the treatment of MBD varies widely from species to species.
READ ALSO: Crested Gecko Shedding – Signs, How Often + How to Help
MBD and Phosphorus Absorption
MBD is also known as Nutritional Secondary Hyperparathyroidism (NSHP) within veterinary practices, so your vet may diagnose this in your reptile that is suffering from MBD. In response to low calcium levels (hypocalcemia) the parathyroid glands secrete a hormone that tells the body to start freeing stored calcium from the bone into the blood. It also blocks the absorption of phosphorus in the kidneys so that they can take in more calcium. If the cause of secondary hyperparathyroidism is not nutritional (lack of calcium), then it’s possible the kidneys are in distress, and thereby not converting enough vitamin D or process phosphate, allowing calcium phosphate to continually suck up calcium from the bloodstream. The process loop for this system can snowball if there is any disruption, which creates further deterioration of the process. Hyperparathyroidism is the internal disruption that leads to the physical signs we label Metabolic Bone Disease.
Frugivorous reptiles like crested geckos are especially susceptible to MBD because of improper supplementation and the use of baby food. Many new keepers are told that baby food is an acceptable diet and so they don’t supplement and they might not feed anything else. Most fruits are high in phosphorus and low in calcium, which will create a calcium deficit and result in MBD over time. Dusted insects can help, but it’s not going to fix the problem if they are an occasional treat.
Feeding homemade diets or baby food is not recommended and should be used only as a treat (once a month or so). A well-established brand of commercial diet should be the basis of your crested gecko’s diet to prevent MBD and other nutritional deficiencies. Dusted feeder insects can provide balanced levels of calcium, vitamin D3 and other nutrients to prevent a calcium deficiency.
Calcium Crash and MBD
Breeding females are susceptible to a “calcium crash” as their available calcium is used for producing eggs. Crested geckos have calcium sacs in their mouths to store calcium. Checking them is a good idea if you are acquiring a new crested gecko or have a breeding female. Proper diet again will keep females from a calcium crash which can lead to crested gecko MBD over time.
For details on how to check calcium levels, watch this great calcium sacs video from JB Cresties‘ crested gecko health information.
Medical Treatment for MBD in geckos
If your gecko shows signs of a calcium deficiency, such as shaking her head, swollen limbs or zig-zag tail, consult your reptile vet. They may recommend liquid calcium by mouth which can be administered at home as well as treatments given by your veterinarian or vet technician. A vet can perform X rays to evaluate the level of bone deterioration and provide supplemental fluids. A UVB light may also be recommended for at-home care.
Increasing calcium supplementation with vitamin D3 and UVB light will improve minor cases. If you’re using UVB light on your crested gecko, I recommend Miner-ALL’s Outdoor formula. Without UVB, Miner-ALL’s Indoor formula will be more suitable. (If you aren’t using UVB and your crested gecko has MBD, I recommend strongly considering installing one. Instructions on which UVB bulbs are best can be found here.) Veterinary care is recommended for more severe cases or cases that do not improve after a couple weeks of treatment.
MBD is particularly easy to prevent in crested geckos. Using a powdered diet from Pangea, Repashy, or Clark’s, providing a 5% UVB bulb, and dusting all insects with calcium powder will prevent the problem from ever surfacing.
Check your gecko’s calcium reserves by periodically examining the white calcium sacs on the roof of his/her mouth.
Can gecko recover from MBD?
Fortunately, if detected early enough, MBD can often be corrected and reversed by making changes and improvements to the husbandry of the animal by providing the needed or adequate levels of UV-A and UV-B lighting and heating, proper supplementation, and other nutrients.
Soon many new keepers became breeders who passed on the notion that all crested geckos needed was babyfood and crickets, with an occasional dusting of calcium. This has led to numerous cases of MBD and other nutritional imbalances which can permanently cripple and even kill a crested gecko.
Sadar finds that juvenile reptiles are the most likely suspects for MBD, and sometimes, it takes owners a long time – two to three months after purchasing their pets – to visit a veterinarian.
Is an arched back a sign of MBD in crested geckos?
An arched back is also a sign of stress – crested geckos do it to look bigger and to scare you off. Also, chirping, growling or squeaking noises when handling can indicate that your crested gecko is unhappy and stressed. Many crested geckos get scared when you approach, but when you start handling them, they calm down.
With a little bit of coaxing your crested gecko should open its mouth wide revealing its calcium sacks. If the calcium sacks are round and white your gecko is in good health and you’re doing well with supplementation. If they are grey or black your gecko could use added calcium to its diet.
What are calcium sacs in crested geckos?
Crested geckos have calcium sacs in their mouths to store calcium. Checking them is a good idea if you are acquiring a new crested gecko or have a breeding female. Proper diet again will keep females from a calcium crash which can lead to crested gecko MBD over time.
Don’t worry if a male crested gecko has significantly smaller calcium stores than a female yet is eating the same diet, male crested geckos don’t need to store or absorb as much calcium as a female to be healthy as much of the calcium females absorb goes towards egg production whether the eggs are fertile or not.
Prevention of MBD
To prevent hypocalcemia, owners need to understand how to supply both proper UVB light and adequate dietary calcium to their reptiles. Dr. Whittington explains that one common mistake owners make is using plant grow lamps to supply light for their reptiles. These lamps supply the UVA light needed by plants but do not supply UVB rays. Many people put their reptiles near windows to get sunlight, unaware that plastic and glass block UVB rays. A proper set-up will allow UVB rays from a lamp to reach a reptile without any obstruction. Placing a mesh screen between the lamp and the animal, for example, will allow UVB rays through.
Of course, even if a reptile produces enough vitamin D3, plenty of dietary calcium must also be provided for a reptile to absorb what it needs. Some store-bought reptile foods, such as crickets, are low in calcium. Too much phosphorus can interfere with calcium absorption, so maintaining a proper calcium/phosphorus balance in the diet is also important.
If a reptile is diagnosed with hypocalcemia, the first step is to determine the cause. A veterinarian can rule out kidney disease, which causes calcium to be eliminated through urine. If the deficiency is caused by a lack of calcium intake or absorption, the next step is to maintain proper hydration, decrease dietary phosphorus, and increase dietary calcium and UVB exposure. Calcium can be supplemented orally or can be injected. Also, injections of vitamins A, D, and E can help jump-start calcium absorption by the gut.
With metabolic bone disease, blood calcium levels may appear normal because calcium is taken from the bone to maintain normal levels. In this case, injections of the hormone calcitonin can help bring calcium back into bones, but only if blood calcium levels are sufficient.
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