Vitamin D is made in the skin and provided in supplements and foods such as oily fish and eggs. Both are converted in the liver to form 25(OH)D3 which is the form of vitamin D in the blood, measured by this test. Your levels of 25(OH)D3 levels shows your body’s production plus your intake.

Vitamin D deficiency is linked with many chronic diseases, including autoimmune diseases, diabetes, cardiovascular disease, cancer as well as cognitive decline. Many diseases are more prevalent in the Northern hemisphere due to lack of direct sunlight.

Optimal levels of 25(OH)D3 are certainly above 32ng/mL (80 nmol/l) and ideally over 40ng/ml (100nmol/l)