Many clients come to me with blood test results showing low levels of vitamin D. If the doctor reviews the results, he or she typically puts the client on a supplement with 5,000 or 10,000 ius. This may be warranted but studies are now showing that vitamin D can become toxic if taken in high doses for long periods of time.
I recommend that clients start supplementation if results are low but that they retest after a few months to check levels. If the serum level have increased we can reduce supplementation to a maintenance dose. The client should test again in a few months to confirm that the maintenance dose is the right amount.
in addition, I only recommend supplements that also include vitamin A and vitamin K2. Vitamin K2 is different from K1. K1 helps blood to clot and is found in leafy green. K2 is made in the body and mainly found in animal products and some fermented foods. K2 is needed to get vitamin D and calcium out of the blood and into cells. The risk of toxic levels in the blood with vitamin D supplementation is reduced when combined with vitamin K2.
You may be wondering... what are healthy levels of vitamin D? That will vary, based on health status, other health conditions, genetics and demands placed on the body. For healthy individuals a level of 40 Ng/Ml is sufficient. People with autoimmune conditions, genetic SNPs affecting D absorption and athletes may be better with higher levels of around 50 or 60 Ng/Ml.
It's also important to remember that the body can make vitamin D from sunlight but that requires exposure without sunscreen and adequate cholesterol levels. That's right, enough cholesterol so I don't advise clients to go too low on cholesterol but that's another blog post. Don't be afraid to get outside without sunscreen on your body but move to the shade once your skin starts to turn pink.
For more information on vitamin D functions and concerns over toxicity, see this article by Chris Kresser.