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Vitamin D: when to ask for labs

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Vitamin D is one of the 4 fat-soluble vitamins that have been shown to play a role in IBD and the immune system.  Research has consistently shown that during times of active inflammation, for example, when a person is in a flare, vitamin D levels start to decline.  

The questions that we start asking ourselves is why vitamin D is an important marker to monitor and reasons for maintaining healthy levels.  Continue reading on to learn more about why vitamin D and IBD work well together. 

Vitamin D and IBD

According to the National Institutes of Health (NIH), roughly 60%-70% of patients with IBD do not meet optimal vitamin D levels.  Some research has even shown that vitamin D deficiency can play a role in the development of IBD (1).  

Furthermore, research has shown that extraintestinal manifestations from IBD including osteoporosis, can develop due to a pre-existing vitamin D deficiency.

In animal models, vitamin D supplementation can be part of a treatment plan for colitis and in patients with IBD, low levels of vitamin D can increase the risk of relapse in disease (1). Vitamin D is not only a fat-soluble vitamin but also a hormone that contributes to a healthy immune system.  

When vitamin D supplementation is needed

It is recommended for all IBD patients to be screened for a vitamin D deficiency, especially during times of active inflammation since IBD can affect nutritional status. The specific lab marker (through blood) that is recommended to be checked is 25-hydroxy vitamin D or 25(OH)D.  

Risk Factors for Low Vitamin D:

  • Those with active disease (high inflammation)
  • Those with IBD affecting the small intestine (jeujenum)
  • Those living in northern hemispheres or cold temperatures that require skin coverage
  • Those with IBD (30-40% of us are low)
  • Those with olive & darker skin tone

For those with suboptimal levels of vitamin D which is between 20 and 29 ng/mL or a vitamin D level of less than 20 ng/mL should be supplementing with vitamin D3 appropriately.  Once a person starts supplementing with vitamin D, blood levels for 25(OH)D should be monitored after 3 months of treatment. 

When & How to Ask for Vitamin D levels

If you’ve got IBD – we suggest checking your levels with your annual lab work. However, if you’ve been found to have low Vitamin D or find you are consistently low – you may want to check more frequently than just once per year.

Asking your doctor for a vitamin D level can be helpful for you and your IBD.  Asking can look something like:

“I would really like to measure my vitamin D levels because I have been supplementing and because I understand the relationship vitamin D has to my IBD.”  

If you receive pushback from your doctor, ask them what their reasoning is and then again, address your concern for measuring your levels. Because vitamin D is a fat-soluble vitamin, it is important to continue monitoring. 


  1. Ananthakrishnan AN. Vitamin D and Inflammatory Bowel Disease. Gastroenterol Hepatol (N Y). 2016 Aug;12(8):513-515. PMID: 27917088; PMCID: PMC5114499.