What does a vitamin D level of 40 mean?

A vitamin D level of 40 ng/mL is considered optimal. This means you are likely getting enough vitamin D from your diet, supplements, and/or routine sun exposure to support healthy bones, immune function, and overall health.

Not only is a level of 40 ng/mL good for your overall health, it also puts you at lower risk for certain upper respiratory infections (including COVID-19 and the flu), as well as type 2 diabetes and some autoimmune diseases, like multiple sclerosis, type 1 diabetes, and lupus [4,5,6,7].

How to maintain optimal vitamin D levels

• Continue consuming plenty of vitamin D-rich foods by eating foods like salmon, herring, canned tuna, eggs (with the yolk), and fortified milk, yogurt, and breakfast cereals

• Get 10–30 minutes of unprotected midday sunlight most days

• Continue to take a vitamin D supplement if you were supplementing previously

• Check your vitamin D level at least every 6 months (summer and winter) to ensure your levels don’t fall below 40 ng/mL. If your level falls in the winter, you may need to start supplementing or increase your supplement dose to maintain optimal levels.

• If you start a new medication, inquire about interactions with vitamin D.