# Vitamin D

Source: https://synapse-lifestyle.com/en/reference-guide/biomarkers/vitamin-d

Unit: ng/mL

## What is Vitamin D?

You produce vitamin D mainly under the influence of sunlight on your skin. It works throughout your body, from bones to immune system. A healthy value supports your bones, muscles and resistance. In our regions a shortage in winter is very common.

## Clinical frame

**25-hydroxyvitamin D or 25(OH)D is the main marker of vitamin D status** and reflects the reserve built up over the past weeks. Vitamin D plays a central role in calcium balance and is essential for normal **bone and muscle function** [3].

A deficiency can lead to reduced calcium absorption, muscle weakness and bone demineralisation [2]. There is, however, **no full international consensus** on the optimal target value, especially for values between 20 and 30 ng/mL [3].

Low vitamin D values are also associated with **insulin resistance and cardiometabolic dysregulation**, but a causal link has not been sufficiently demonstrated [1]. Correcting a deficiency is therefore the main goal; **aiming for higher values offers no proven additional benefit** [2].

## What moves this value?

Little daylight, the winter months, covered skin and getting older lower production. Your skin type also plays a part.

Regular daylight and, especially in winter, a supplement bring this up to level slowly but reliably. Discuss the right amount with your doctor.

Developed and reviewed with the Synapse [medical advisory board](https://synapse-lifestyle.com/en/advisory-board).

## References

1. Lei, X. et al. Serum and supplemental vitamin D levels and insulin resistance in T2DM populations: a meta-analysis and systematic review. Scientific Reports 13, 12343 (2023). https://doi.org/10.1038/s41598-023-39469-9
2. Rebelos, E. et al. The Role of Vitamin D in Health and Disease: A Narrative Review on the Mechanisms Linking Vitamin D with Disease and the Effects of Supplementation. Drugs 83, 665–685 (2023). https://doi.org/10.1007/s40265-023-01875-8
3. Cesareo, R. et al. Clinical Management of Vitamin D Deficiency in Adults. Nutrients 10, 546 (2018). https://doi.org/10.3390/nu10050546

- [All biomarkers in the guide](https://synapse-lifestyle.com/en/reference-guide#biomarkers)

The colour zones are personal: they depend on age, sex, risk and history, and appear in the patient's own report.

Insights to discuss with the patient, not a diagnostic instrument.