As is the case with just about any condition, the signs and symptoms of iron deficiency can vary from person to person. Typically, deficiency happens in three stages. In the first stage, iron stores are depleted, but you may not notice anything different. If iron loss continues — or if your intake of the mineral doesn’t improve — that’s when you may begin to notice symptoms. This first stage can be detected by getting blood work done and seeing a decrease in ferritin levels (a protein that helps store iron in your cells).

In the second stage, there will be a decrease in iron transporting throughout the body, and in the third stage, hemoglobin will drop due to the reduction of iron. This final stage results in anemia, as noted in the 2014 review paper. In the second and third stages of deficiency, you may notice a range of different symptoms varying from lethargy to irritability, and even the inability to concentrate. In addition to these symptoms, more physical sensations as explained in an article published in a 2001 issue of the Journal of Nutrition, include rapid heart rate, palpitations and heavy breathing during exertion.

As iron deficiency progresses through the stages, athletes and active individuals will begin to experience different effects on their performance. The ability to get through seemingly easy cardio or strength workouts may dwindle, and the effects of training might even become impaired. A 2019 review published in the European Journal of Applied Physiology explained the effects of iron deficiency. Low iron interferes with the body’s ability to optimally transport oxygen to the muscles. This causes a greater demand on anaerobic metabolism (the breakdown of carbohydrates and fat for energy when oxygen isn’t available). And the muscles’ glycogen stores (carbohydrates that are stored in the muscles and used for energy during physical activity) will deplete faster than usual.

Though these symptoms may be vividly apparent in some, the only way to know if you have an iron deficiency is to get a blood test. Early detection is ideal in order to prevent impaired performance and impairment to overwell wellbeing. The 2019 review done in the European Journal of Applied Physiology suggested that for those with no symptoms or history of iron deficiency it’s fine to get tested annually; however, for individuals who are at risk, blood tests should be done at least twice a year. And as a quick reminder, people who are at risk of this mineral deficiency include vegans, vegetarians, females with irregular menstrual cycles, anyone with a past history of iron deficiency or unexplained levels of fatigue (despite adequate rest), and endurance sports participants (such as those who do long-distance running).