A remarkable process: Vitamin D3 Synthesis and your Reptile

UV-A and UV-B are both necessities for your reptiles health and well-being.

As responsible reptile keepers, we all strive to create a thriving life for our reptiles! We do this by mimicking their natural environment through the use of technology. The closer we are able to replicate their environment in the wild, the better their bodies can perform in captivity.  

The Vitamin D3 synthesis is one of the most extraordinary biological processes a reptile goes through! Here we break down the entire process and why we stress the importance of lighting!  


The process begins with our reptiles and the production of a hormone called proVitamin D within their skin cells. Upon exposure to the sun or UVB provitamin D is converted into previtamin D. Previtamin D is then isomerized through the exposure of warmth into vitamin D3.

Once this process occurs, the skin then releases the vitamin D3 from the skin. The vitamin d will bind to a vitamin d binding protein so that it can be distributed to the rest of the body through the bloodstream.  

The bloodstream will carry vitamin d to the liver where it is converted into a hormone called calcetriol. Calcetriol is distributed through the body until it reaches the liver where some of the cacetriol is then converted into calcediol.

What’s the significance of calcitriol and calcediol?

  • Calcetriol is the substance that is test in a reptile blood sample to determine the vitamin d status of your reptile!
  • Calcediol plays an important role in calcium metabolism. It controls he absorption of calcium from the gut and sometimes even the bones (if your reptile is deficient, this is what causes MBD). Studies proved that calcediol improves the immune system, organ functions, and preventing cells from becoming cancerous.  

** It’s important to note that supplementing your reptile with vitamin d3 could be harmful. Vitamin D3 is toxic in large amounts! Providing adequate lighting will allow vitamin d3 to be created and processed naturally within your reptile. Providing too much vitamin D3 causes kidney damage, calcification of soft tissues and major blood vessels, and even premature death.

A reptile is fully capable of controlling how much vitamin d3 is distributed in their bodies because of safety mechanisms in the body prevent overproduction. A reptile provided with basking light and UVB will produce and regulate d3 on their own. Its best to let your reptile work through this biological process on their own as It’s nearly impossible to know exactly how much D3 your reptile needs through supplementation.


chart showing the process of vitamin d3 synthesis



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