- Target blood levels of 40-60 ng/ml (UK test results are given in 'nanomoles per litre' so for patients living in UK you should be looking at reaching and maintaining a level of at least 100-150 NMOL/L)
- Serum concentration of 25(OH)D is currently the main indicator of vitamin D status. It reflects vitamin D produced endogenously and that obtained from foods and supplements [1]. In serum, 25(OH)D has a fairly long circulating half-life of 15 days [1]. Serum concentrations of 25(OH)D are reported in both nanomoles per liter (nmol/L) and nanograms per milliliter (ng/mL).
- One nmol/L is equal to 0.4 ng/mL, and 1 ng/mL is equal to 2.5 nmol/L
- Recommended intakes for vitamin D are 400-800 IU/d from government agencies in US, Canada and UK, but to reach a target level of 40-60 ng/ml may take up to ten times as much and taking 4000 IU a day is considered safe for every adult.
See here for helpful information on optimal vs sub-optimal D3 levels