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Vit D3 - levels required for immune health

  • 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


Sandy you have done it again, this article is so precise, conversion rates, plus the colorful simple and to-the-point explanatory table.

I have been taking this wonderful vitamin for years, and would like to think that it has helped me to shrug off the usual winter snivels.

Hope it will help when we have to go to our clinic to have the covid vacc. on Tuesday, which is forecast to be a VERY cold snowy day....


Great summary.

I just had a blood vitamin D level test completed a few days ago and it came back right at 50 ng/ml (125 nmol/L). The level I prefer is 70 ng/ml (between 50 - 100 ng/ml) and despite my taking 7,500 IU's per day (5,000 one day; 10,000 next day), my D level still fell during this winter from my September peak. Blood testing is very important so you know your blood level. As summer approaches and I feel the warmth of spring, I will cut back to my summer intake of 5,000 IU's per day except on days when I am in the sun at the beach.

How much D3 you need to supplement is individual to you, so get tested and know your blood level.

and some more information for those who may be worried about excess sun exposure on the skin.

 Vitamin D produced in the skin also helps protect the skin

I just got tested and I am at 90.7 ng/ml!!? I take 5,000 IU every other day and lives in California.   

Excellent! You are in the sweet spot for vitamin D (50 - 100 ng/ml). On days when your skin is exposed to California sun, you may even avoid taking any vitamin D3.

Something about California and sun ... (I presume you live in southern California)

How much of vitamin D supplements do you take on a daily basis ??

I take vit D3 5,000IU/ vit K2 180mcg every other day. But I live in Southern California (lots of sun).