What Is a Normal Vitamin D Level? Why New England Winters Change the Answer

Rocha says there is no consensus among the major societies. The National Academies framework, as summarized by the NIH, calls a level under 12 ng/mL a risk of deficiency, 12 to 20 potentially inadequate, and above 20 adequate for most healthy people, and he points out those reference points were built mainly around skeletal health and calcium. The 2011 Endocrine Society guidelines used higher thresholds and commonly led clinicians toward a target of 30 or above. The 2024 Endocrine Society guidelines replaced them, stating that outcome specific thresholds have not been established in trials for generally healthy people, and now recommend against routine screening in healthy adults. Rocha says he does not agree with the National Academies cutoffs and is not sure he agrees with the recommendation against routine screening either. In his view, what counts as sufficient for a given person is decided by the clinician and the patient together.

Latitude. Rocha cites research that tested winter sunlight in Boston, at about 42 degrees north, and found that from November through February cloudless winter sunlight produced no detectable pre-vitamin D3 in the skin samples. Maine and New Hampshire sit further north than Boston. He calls it a vitamin D winter: the sun can be shining while the UVB reaching the ground is not enough for meaningful vitamin D production in the skin. He also cites a study of 2,298 older adults where the average seasonal swing from peak to trough was 9.6 ng/mL, and larger at higher latitude, so a level drawn in February and one drawn in August can reflect two seasons rather than two different people.

Rocha says fatigue can occur and is real, but it is non-specific. Severe and prolonged deficiency can cause bone pain or tenderness, weakness in the muscles closer to the center of the body (trouble rising from a chair or climbing stairs), osteomalacia, and rickets in children. Vague symptoms plus a mildly low number is not the same thing as a deficiency syndrome. Before blaming vitamin D for fatigue, aching or low mood, he wants to look at iron and ferritin, a complete blood count, thyroid, B12, sleep quality including possible sleep apnea, mood and seasonal changes, caloric intake, activity level, medications and inflammation.

Rocha frames risk around production, intake, absorption and metabolism. Higher risk situations he names include minimal sun exposure or spending most of the time indoors, older age, darker skin pigmentation, malabsorptive conditions such as celiac disease or inflammatory bowel disease, higher body weight, certain medications that affect vitamin D metabolism, chronic kidney or liver disease, and infants depending on their feeding and supplementation. He singles out people who have had bariatric surgery, who he says should have nutrient testing at least yearly. A risk factor does not mean disease, he adds; it changes how likely a low result is.

Rocha says he always combines vitamin D with vitamin K2. Vitamin D helps the body capture calcium, and calcium levels that run too high can lead to calcification, which is a problem in the arteries or the kidneys. He describes K2 as the traffic cop that tells calcium where to go. He also says it is possible to overdose on vitamin D, so high doses should not be taken without monitoring, and that he rarely sees K2 recommended alongside high-dose vitamin D in conventional care.

A viewer asked this in the live Q&A, and Leah noted that a personal answer would need a look at that viewer's labs. Speaking generally, Rocha said vitamin D can be dosed weekly or daily and both work. The vitamin K2 studies he referred to were done on a daily schedule, and how K2 behaves on a weekly schedule is not known, so in his words the jury is out.