New guidelines could double the number of Americans diagnosed with iron deficiency

New diagnostic guidelines issued by the American Society of Hematology could roughly double the number of Americans flagged for iron deficiency, by raising the blood-test threshold doctors use to catch the condition before it becomes severe.

The society's new standards, the first it has ever issued specifically for diagnosing iron deficiency, raise the ferritin level that doctors should treat as a warning sign, replacing decades of inconsistent, informal cutoffs that varied from one clinic to the next. Ferritin is a protein that reflects how much iron the body has stored; under the old informal standard, doctors generally flagged deficiency only when ferritin fell below 15 nanograms per milliliter. The new guidance sets the threshold at 30 ng/mL or below for most adults, and at 50 ng/mL or below for women who experience heavy menstrual bleeding, according to the society and reporting by NBC News.

The change reflects growing evidence that the old cutoff was missing large numbers of people with clinically meaningful iron depletion, in part because ferritin results can vary between labs and because the original threshold was set decades ago using data that undercounted symptomatic patients. "Iron deficiency is very common, very underdiagnosed and therefore very undertreated," Dr. Ariela Marshall, a hematologist, told NBC News.

Who is most affected

Iron deficiency is already common. Research cited by the society found that a substantial share of American adults have some degree of iron deficiency, with the rate notably higher among teenage girls and young women, a pattern researchers attribute in part to menstruation and inadequate dietary iron intake during adolescence.

Women of childbearing age face the highest risk, particularly those with heavy periods, which can deplete iron stores faster than diet can replenish them. Other groups at elevated risk include people with irritable bowel syndrome, endometriosis, uterine fibroids or celiac disease, as well as those facing food insecurity, which limits access to iron-rich foods like red meat, beans and leafy greens, according to the ASH press release announcing the new standards.

Iron deficiency can cause fatigue, hair loss, brittle nails, difficulty concentrating and restless legs at night, symptoms that are often dismissed or attributed to stress, poor sleep or normal aging — especially when a standard blood test comes back "normal" under the old, stricter threshold. Doctors say the new guidelines should prompt more of those borderline cases to be flagged for treatment, which can range from dietary changes and oral supplements to intravenous iron infusions in more severe cases.

Hematologists involved in drafting the standards say the goal is not to encourage unnecessary testing, but to make sure ferritin results are interpreted consistently so that patients with real, symptomatic deficiency are not reassured by a technically "normal" number. For patients with persistent fatigue or other symptoms, doctors say, the new thresholds are a reason to ask whether their last ferritin test would still count as normal under the updated standard, and to request a repeat test if it has been more than a year or two since their iron levels were last checked.