Researchers at Loyola University Medical Center reviewed over 1,000 previous studies.
The conclusion is that more doctors should change the cutoff level for Vitamin D.
Older guidelines say people need Vitamin D if their blood levels are at 30 nanograms per millimeter.
But newer recommendations from the Institute of Medicine say you can lower the threshold to 20.
The Loyola study published in the journal Plos One supports those guidelines.
It finds people with levels between 20 and 30 have no higher risk of death than those with normal levels.
That small shift would decrease the number of Americans being treated with Vitamin D by nearly 80 million.
The study's author says patients confused about how much Vitamin D they need should consult their doctor.
"I think it is important to know your actual Vitamin D level because there is a lot of controversy, so if you have a Vitamin D level that's between 20 and 30 you may have differing opinions from different doctors whether or not you would benefit from Vitamin D supplementation," said Holly Kramer, nephrologist at Loyola University Medical Center. "If you level is less than 20 i think most people would say you would benefit from vitamin d supplementation."
Vitamin D is considered essential to avoid poor bone health.
But there are conflicting reports whether it can protect against other diseases.
Also too much Vitamin D can damage the kidneys and heart.