Are calcium supplements necessary for blue-tongue skinks? Do they receive enough calcium just from their diet alone? Here’s what I found. 

So, is providing calcium supplementation to captive blue-tongue skinks necessary?

The answer is yes, you will need to provide a calcium supplement to your blue-tongue skink. This is for 2 reasons. First, to ensure that your blue-tongue gets enough calcium to stay healthy. Second, to ensure that the calcium level in your blue-tongue remains higher than the phosphorus level. 

Why can’t your blue-tongue get enough calcium from its diet?

What does phosphorus have to do with your skink’s calcium supplementation?

Unfortunately, it’s a little complicated but I’ll do my best to simplify everything as best as a I can.

Do Blue Tongue Skinks Need Calcium?

In order to stay healthy, an abundance of calcium in the body of a blue-tongue skink is absolutely necessary.

Calcium (Ca) itself is actually a mineralis found in the bodies of vertebrate animals, and is needed for and in order to regulate:

  • healthy bones and teeth
  • the development and strength of bones
  • blood coagulation
  • muscle movement
  • heart health

However, there is also something called phosphorus, which is also extremely important.

Phosphorus and calcium have a vital inter-related relationship.

Why Phosphorus is Also Important 

Phosphorus (P), like calcium, is also needed for the healthy development and strength of bones and teeth.

It’s also needed for:

  • the creation of protein
  • aids in the process of cell and tissue repair
  • helps to store energy
  • crucial for several metabolic processes
  • supports healthy kidneys
  • assists in muscle movement
  • maintenance of a healthy heart

Phosphorus, like calcium, is extremely vital in the maintenance and aid of several bodily processes.

Phosphorus and calcium also have a very special relationship. 

You see, when phosphorus comes into contact with calcium, the two bind together and form calcium-phosphate. 

Here’s the thing:

  • a deficiency in phosphorus in blue-tongue skinks is nearly impossible to achieve
  • a deficiency in calcium in blue-tongue skinks is relatively easy to achieve

Basically, your blue-tongue skink needs a whole lot more calcium than phosphorus.

When the phosphorus binds to the calcium to form calcium-phosphate, it depletes the skink’s body of calcium.

Thus, the goal of any diet you have should be to ensure that your bluey has an excess of calcium. 

This is in order to prevent something called metabolic bone disease (MBD).

Metabolic bone disease is an extremely serious matter.

For starters, if it develops, not only is it very painful for your blue-tongues, but also:

  • can lead to your bluey’s limbs and muscles twitching involuntarily
  • can lead to partial paralysis, being crippled and possibly the death of the animal

One of your most important jobs as a blue-tongue owner is to ensure that your pet has enough extra calcium in its diet to protect against metabolic bone disease. 

How exactly do you figure this out?

Here’s where it gets a little more complicated.

How Much Calcium is Enough? 

So here’s the thing.

Your bluey needs both calcium and phosphorus. But

  • if it receives too much phosphorus, this will draw calcium away from its bones, and this can eventually lead to metabolic bone disease
  • too much calcium however can cause digestion issues, and could potentially lead to partial calcifying of its internal organs

The main thing here is that you give your bluey more calcium than phosphorus, so that the residual calcium left can be absorbed into the body.

How much more calcium than phosphorus is ideal?

A good ratio of calcium to phosphorus is 2 parts calcium for every 1 part phosphorus, or 2:1. 

This way there is plenty left over after the phosphorus binds to the calcium.

TC Cooper from ReptileMountain TV did some research and found that most dog food brands, on average have about 0.3% calcium and 0.2% phosphorus. So, not quite a 2:1 ratio, but fairly close.

Zignature has a bit more, at 0.55% calcium and 0.366 phosphorus. Again, not quite 2:1 but still fairly close.

Ideally, as a part of your bluey’s total diet (including dog food, vegetables and supplementation), you want the calcium portion to be between 1% and 2%.

Most of your bluey’s calcium will come from 2 sources: 

  • premium canned dog food, such as Zignature’s line
  • calcium supplements

The amount of calcium found in most of the vegetables you would be giving your skink is so minute it doesn’t even matter.

A good portion of your skink’s calcium will come from the dog food. 

Now, since we know that with most dog food brands, we aren’t quite hitting that 2:1 ratio, and to absolutely be certain that we aren’t giving too much calcium to our animals, the next question becomes…

How much calcium to supplement with?

A good rule of thumb is:

  • “a little, often”

Here’s what this means exactly:

  • take 1 PINCH of calcium supplement and lightly dust your bluey’s food, either EVERY meal or EVERY OTHER MEAL for dog food 
  • take 1 PINCH of calcium supplement and lightly dust your bluey’s greens, every 3rd or 4th meal (if you feed it solely vegetables on alternating days)

If you want to make sure your calculations are as precise as possible, in order to hit that 1% to 2% calcium as total part of diet, this works out to around:

  • ~3 grams of calcium supplementation per dog food can (assuming your can of dog food is between 300-400 grams, as most are) 

Anything over ~6 to ~7 grams per can of dog food and your ratio of calcium to phosphorus is going to be much higher than you need it to be.

So, you don’t need to put heaping tablespoons into your dog food. A pinch lightly dusted will be sufficient.

Remember, although you don’t want to be giving too much calcium, it’s a lot harder to over-supplement with calcium than under-supplement it.

With all of that said, this brings me to my next point, which is…

What’s the Best Calcium Supplement? 

There are a ton of different reptile calcium supplements on the market and they all aren’t equal.

How can you easily filter some of them out?

Here’s a good rule of thumb:

  • only consider calcium supplementation that is phosphorus-free
  • only consider calcium supplementation that comes with D3

You’ll want to avoid the phosphorus, as your skink will get enough of that from its regular diet.

However, you’ll also want to look for supplements that contain the vitamin D3, as chances are, your skink is not getting enough D3 from your UV light bulb (unless you are measuring it and being super precise about hours and distance to UV bulb, that sort of thing, which I highly doubt!).

Here’s the thing about reptile calcium supplements:

  • they all have EXTREMELY different amounts of D3 in their products 

Some products have literally 20x to 30x as much vitamin D3 in their product, versus other popular brands.

That’s how skewed the level of D3 in these supplements are.

For instance, on the nutrition label from Zoo Med’s Repti-Calcium it says…

The vitamin D3 component is listed at 10,390 IU.

IU means international parts per pound.

And yet, on a can of Fluker’s Calcium it says…

Each serving size with this is listed at 100,00 IU.

There is literally 10x as much vitamin D3 in the Fluker’s as there is in the Zoo Med Repti-Calcium!

And Rep-Cal Phosphorus-Free Calcium with Vitamin D3…

There is 400,000 IU, which means 4x as much as the Fluker’s! 

So, what’s a good IU number for your pet skink?

A good rule of thumb is…

…60,000 to 100,000 international parts per pound. 

However, this isn’t a hard and fast rule, and as long as you aren’t putting heaping teaspoons of calcium supplement loaded with 400,000 IU of vitamin D3, you aren’t going to harm your animal.

Remember, it is more difficult to under-supplement than over-supplement when it comes to these types of things. 

That being said, too much of anything tends to be a bad thing.

Too much vitamin D3 in your bluey’s diet can, like too much calcium, lead to eventual health problems.

How do you avoid this?

Here’s my advice:

  1. Choose a calcium supplement that is < 100,000 IU for vitamin D3.
  2. Add ~3 grams of calcium supplement for every 1 can of premium wet canned dog food
  3. If you don’t have a measuring device, add a pinch of calcium to your staple food (or dog food) every meal or every other meal, and very lightly dust the greens that you give your blue-tongue every 3rd or 4th meal.

Lastly, measuring out the vitamin D3 in your calcium supplement will prove useless if you don’t have a UV-B light set-up in your skink’s terrarium.


Because blue-tongues need UV-B in order to process and metabolize the vitamin D3 that they have consumed. Without it, it will not be absorbed.

So, make sure your UV-B light is in good working order, or all of this will prove to be useless. 

To sum everything up:

  • blue-tongue skinks need calcium supplementation
  • they also need phosphorus, but they will receive enough of this from the foods that you provide (typically a home brew, wet canned premium dog food, insects and greens)
  • about ~3 grams of calcium supplement should be sufficient for every can of dog food (or add a pinch every or every other dog food meal)
  • use a calcium supplement that is phosphorus-free, but has vitamin D3
  • use a calcium supplement that is listed at <100,000 IU for vitamin D3
  • make sure your UV-B light is working in order for your bluey to metabolize and process the vitamins

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