 What do you do if you're one of the 42% of Americans with vitamin D deficiency are put on a vitamin D supplement regimen, and your levels still don't budge? That kept happening to this group of docs at the Cleveland Clinic. In our practice, they wrote, it is common to see patients treated with vitamin D supplements who do not achieve an appreciable rise in their vitamin D level after therapy despite large prescribed doses. So they did a few experiments and concluded that taking vitamin D with the largest meal improves absorption and results in higher blood levels of vitamin D. Just that one simple change in timing results in about a 50% increase in blood levels of vitamin D achieved. They conclude it therefore seems reasonable to ask patients to take vitamin D supplements with their largest meal, because it may be a cost-effective strategy that could very well help patients to achieve optimal serum levels of vitamin D.