Calcium deficiencies are usually grouped under the umbrella term of Metabolic Bone Disease or MBD. The issue is quite common in reptile husbandry but in my opinion it shouldn't be anymore. As a matter of fact, I feel the issue should be extinct when it comes to reptiles as we really have no excuses to not provide adequate husbandry to our reptiles to allow for proper calcium absorption. Sorry about the misleading title, as there is really no secret to avoid calcium issues. The information is right in front of us but we don't seem to grasp it at times. I am hoping this thread helps as many people as possible to avoid the heartaches that come with dealing with calcium deficiencies. Reptiles need calcium to grow, to produce eggs, and to move around on a daily basis. Calcium is an essential mineral to reptile health but providing our reptiles with a tub of calcium every day doesn't ensure they will get proper calcium in their system. You see, calcium absorption is a process and there are many important steps needed for this process to go smoothly. Yes, availability of calcium is important but calcium can't be absorbed in the reptile's body without vitamin D3. Vitamin D3 is produced naturally in the reptile's body by exposure to Ultraviolet Light B (UVB). UVB is part of the natural, unfiltered sunlight spectrum. So there is the process in a nutshell: A reptile basks in the sun to warm up and to absorb the UVB rays. These UVB rays will trigger the kidneys to produce vitamin D3 which will go into the bloodstream and allow the cells to absorb calcium. That means a strong, happy reptile that can move around, can grow and can reproduce normally. Simple huh? Then why do we still have issues in this hobby with calcium deficiencies? I don't know, but I have a few suspicions that I will list below. 1- Improper exposure to natural UVB- Many keepers think that putting the reptile near a glass window will solve the issue of UVB exposure. UVB will be filtered out by most glass and acrylic so putting a glass tank on a open window doesn't help. Putting a glass tank or a screen cage near a closed window doesn't help.Putting a screen cage in an open window does help. The sun rays need to be as unfiltered as possible for the UVB to be at its best. UVB is also at better levels in the morning hours until about noon. After noon, the levels diminish and are not as strong, but that doesn't mean they are no good. If you can have your choice of sunshine exposure for your reptile, use the AM. Otherwise, use the afternoon as it is better than nothing. DO NOT put your reptile in a rubbermaid tub or glass or acrylic enclosure for sunning, it will cause the reptile to get overheated and die if left unattended. Only screen cages or well ventilated cages (bird cages, etc) can be used for this. 2- Improper exposure to artificial UVB- Many keepers can't take their reptiles outdoors for many reasons and they depend entirely on artifical bulbs for their UVB. Nothing wrong with that as long as the proper bulbs are used and we can make sure proper levels of UVB are being produced. There are many bulbs in the market that only produce UVA but not UVB and keepers buy them thinking that it is a "UV bulb". Well, it is a UV bulb but not a UVB bulb which makes a huge difference. Different bulbs will produce different levels of UVB for different amounts of time and sometimes keepers buy the right type of bulb but it doesn't get changed frequently enough thus leading to little to no UVB exposure over time. This is why it is recommended to change the bulbs every 6-12 months depending on the bulb, or buy a UVB meter which will tell you how much UV is being produced by your bulbs. If you measure a drop in UVB production from your bulbs, then it is time to change them. 3- Excessive reliance on Vitamin D3- There is still some train of thought that if you use vitamin D3 daily when supplementing, then you have no need for UVB. The thinking being that by providing D3 you are bypassing the step in the process where UVB triggers the production of D3 in the reptile's body. It would seem this is a logical step but it fails to show that excessive use of D3 causes severe liver issues and premature death. Reptiles can produce as much D3 naturally as they need with the exposure to UVB but when you provide D3 externally you have no way of determining how much or how little you are actually giving your reptiles. You could be underdosing them thus depriving them of calcium absorption or you could just as well overdose them and cause a whole new set of health issues. Artificial supplementation has it's place in reptile husbandry, but it should not be used to replace the natural way. 4- Availability of calcium- Not all calciums are made the same and some seem better suited for certain reptiles than others. Calcium carbonate is the standard form of calcium used in the hobby but there are other forms of calcium out there that are more bioavailable for reptiles once ingested. What's the catch? Some of the products stick better to insects than others, some products are thinner than others, some taste better than others, and some products clump quicker than others. It is a matter of trial and error when you choose your calcium but make sure you choose one that fits your and your reptiles needs. You will likely need a calcium product that sticks well to insects if you are feeding insectivores, like chameleons, that need to hunt their food. If you are feeding herbivores you can use a less sticky product if you are feeding them from a bowl. If you are feeding carnivores, their food is usually on the moist side when you consider the ones that eat dog or cat food as well as frozen rodents, so you need a calcium that can stick to that food without creating too much of a thick paste that could discourage the reptiles from eating it. Not understanding these factors can lead to the use of a good product that doesn't fit your reptile's lifestyle thus leading to poor ingestion of the calcium and low availability of this mineral in the body. 5- Improper diets- We are what we eat, and so are our reptiles. If we don't provide them with a well balanced diet and depend solely on calcium supplements we might never be able to do right by them. The closest we can get to providing our reptiles to a natural diet (what they would eat normally in the wild), the more likely they are to get as much nutrients as they would in the wild. This would limit the need for extra supplementation and would allow us to develop a system where we alter their diets on a minimal basis rather than every day or so. We can never duplicate nature but we should aim to do it anyway. I am partial to chameleons as they are the reason I became a Veterinarian in the first place. These lizards are about the most delicate species of reptile there is and nutrition is everything to them. Calcium deficiencies are alive and well in chameleons today and they shouldn't be. As much as we know about them and their needs, we should be able to scratch calcium issues off the book of chameleon ailments for good. I really hope that anyone reading this learns something or can pass it along to someone who can use this info. It might be too ambitious of a goal for me, but I sure hope I can see a reptile hobby where calcium deficiencies are an oddity rather than a routine issue. A 2-year old Veiled Chameleon with severe caclium deficiency A baby Veiled Chameleon with calcium deficiency issues.