Feeling constantly tired or struggling to focus is often brushed off as part of being a teenager. New research suggests that for many adolescent girls, low iron levels linked to both menstruation and diet may be playing a larger role than commonly recognized.
In a study published in PLOS One, researchers from Lund University examined menstrual patterns, dietary habits and iron status among nearly 400 teenage girls in Sweden. More than half reported heavy menstrual bleeding, and about 40% were found to have iron deficiency based on blood tests. Girls with heavy periods were three times more likely to have low iron levels, and the risk increased even further among those who limited or avoided red meat.
The researchers combined questionnaire data with blood measurements of hemoglobin and ferritin, a marker of iron stores. While iron deficiency can eventually lead to anemia, many participants already had low iron reserves even when hemoglobin levels had not yet fallen into the anemic range.
“We see a lot of young girls who are tired and distracted. Linking that to menstruation or diet is not obvious,” said Moa Wolff, researcher and associate professor at Lund University and a specialist physician in general medicine at Region Skåne.
Diet played an important role alongside menstrual blood loss. Among girls who followed a meat-restricted diet, nearly two-thirds had iron deficiency, compared with about one-third of those who ate red meat. When heavy menstrual bleeding and a meat-restricted diet occurred together, more than 70% of participants were iron deficient, highlighting how biological and dietary factors can compound risk.
The study also tested a short screening tool known as the SAMANTA questionnaire, which asks six questions about menstrual bleeding. Although previously validated in adult women, this was the first time it had been evaluated among teenage girls. Based on questionnaire responses alone, researchers were able to identify which students were most likely to have low iron levels.
“Many of them only compare with their own previous experiences without knowing what counts as heavy menstrual bleeding,” said Lisa Söderman, a gynecologist and postdoctoral researcher at Karolinska Institutet.
She also noted that many teens were unaware that nonprescription medications can help reduce menstrual blood loss.
Iron plays a critical role in oxygen transport and energy metabolism, and low iron stores have been linked to fatigue, reduced concentration and poorer school performance. The researchers also pointed to longer-term considerations, noting that adequate iron stores before pregnancy are important for maternal and fetal health.
The authors emphasize that the findings do not mean vegetarian or pescetarian diets are unsafe for teens. Rather, they underscore the importance of awareness, monitoring and dietary planning, particularly for girls with heavy periods. The study was conducted in two Swedish upper-secondary schools, and the researchers note that dietary patterns and health care access may differ in other countries.
Taken together, the results suggest that simple screening questions, combined with attention to diet, could help identify teens who may benefit from earlier support to prevent iron deficiency and its effects on daily life.
The study was funded by Region Skåne, the Lions Research Fund Skåne, Regional Funding for Clinical Research (Region Skåne), Karolinska Institutet and Lund University.