Vitamin D

What Is Vitamin D? Deficiency, Testing and Supplementation

Vitamin D helps regulate calcium and phosphorus balance and maintain bone health. It is also important for normal muscle function and immune system function. However, vitamin D deficiency alone does not mean that “immunity is weakened” or that a person will develop many diseases. Vitamin D supplementation has not been shown to prevent cancer or cardiovascular disease. 

How do we get vitamin D?

The body can produce vitamin D in the skin through exposure to sunlight. Production varies depending on factors such as season, geographical location, skin colour, clothing and time spent outdoors. However, prolonged unprotected sun exposure for the purpose of producing vitamin D is not recommended; the risks of sunburn and skin damage should be considered. Vitamin D is also found in oily fish, egg yolks and certain foods fortified with vitamin D. The amount obtained from food may vary from person to person. 

How is vitamin D deficiency identified?

Vitamin D status is usually assessed by measuring 25-hydroxyvitamin D [25(OH)D] in the blood. Symptoms such as fatigue and muscle pain alone do not establish a diagnosis of deficiency; they may have other causes. Routine measurement of vitamin D levels is generally not recommended in healthy adults without symptoms. The need for testing is determined by a doctor, taking the person's medical history and clinical condition into account. 

There is no single, universally accepted target value for 25(OH)D results. Under NIH/NASEM criteria, levels below 12 ng/mL are associated with a risk of deficiency, while levels of 12–20 ng/mL are associated with possible inadequacy; levels of 20 ng/mL and above are considered sufficient for bone health in most people. Levels above 50 ng/mL have been associated with potential adverse effects. These ranges should not be interpreted as definitive diagnostic or treatment thresholds without considering the clinical context. The Endocrine Society does not define a specific target vitamin D level for healthy individuals. 

Is vitamin D supplementation necessary?

The recommended daily intake for adults is generally 600–800 IU, depending on age; these values are dietary reference intakes for healthy individuals, not doses for treating deficiency. The need for supplementation and the dose should be determined by a doctor based on age, diet, health status and medications used. It cannot be said that every healthy adult needs to take high-dose supplements or have a blood test beforehand. 

Excessive vitamin D supplementation can lead to elevated blood calcium levels and cause nausea, vomiting, constipation, weakness or kidney problems. High-dose or long-term supplementation should therefore not be used without a doctor's recommendation. 

If your doctor considers a 25(OH)D measurement appropriate, you can visit our Nicosia or Kyrenia branches for the test. Explore our check-up packages.