Vitamin D 25-Hydroxy is ordered when an individual has low calcium and/or symptoms of vitamin D deficiency. This can appear as bone weakness/softness, or fractures in adults, or as rickets (bone malformation) in children.
The vitamin D test is for individuals at high risk of deficiency. It is used to monitor diseases that interfere with fat absorption. These diseases include cystic fibrosis or Crohn’s disease. This test also monitors the effectiveness of vitamin D, calcium, magnesium, or phosphorus supplementation.
Individuals at risk of vitamin D deficiency include: older adults, individuals who have limited exposure to sunlight, individuals who are obese, or who have fat malabsorption.
Low levels of D 25-Hydroxy are one of the earliest changes that show in individuals with early kidney failure. People with kidney disease also show low levels.
High levels of D 25-Hydroxy show due to diseases that can make vitamin D outside of the kidneys. The two primary diseases related to this are sarcoidosis or certain lymphomas.
Long-term high levels of vitamin D can eventually lead to the damage of certain organs such as the kidneys and blood vessels via calcification. If magnesium levels are low, a physician may supplement both magnesium and calcium in order to eliminate a low calcium level that is resistant to vitamin D.
Patient Preparation: A fasting specimen is preferred, but not required. Patients can fast for 12 hours prior to specimen collection. Supplements containing vitamins or minerals should be stopped 12-24 hours prior to your blood draw. Do not avoid supplements for longer than 24 hours. Sports drinks and energy drinks such as Redbull or Vitamin Water are known to contain levels of vitamins and minerals that would classify them as supplements. Please look at the vitamin and mineral information on your products. If they are considered a supplement, like Ensure, please discontinue them 12 hours prior to specimen collection.