Some useful information here on different measurements used for assessing D3 status. Understanding the difference between nmol/L and ng/ml is important... see the link below for a conversation factor.
"HOW MUCH VITAMIN D DO WE NEED?
If appropriate, doctors can test the levels of Vitamin D (or 25(OH)D), in the blood. When receiving results, knowing which unit of measurement, ng/mL or nmol/L, the blood levels have been measured in is important. In most countries, vitamin D levels are measured using units called nanomoles per litre or nmol/L. In the US and a handful of other countries, levels are measured using nanograms per millilitre or ng/mL.
The two differing units of measurement are much like metric vs imperial and this can lead to confusion about the results. To convert ng/ml to nmol/L multiply the ng/ml by 2.5 for example 50 ng/ml is equivalent to 125 nmol/L."