Low ferritin: an early warning that your iron stores are running low

How iron deficiency develops

Iron loss tends to happen in stages. First, your body pulls from its stores to keep making red blood cells, and ferritin drops while hemoglobin stays normal. If the drain continues, the iron supply to new red cells starts to fall. Only later do hemoglobin and the red cells themselves change, and that is when anemia is diagnosed.

That sequence explains a common frustration: you feel worn out, your complete blood count looks fine, and nobody checks ferritin. MedlinePlus notes that ferritin is often ordered when hemoglobin or hematocrit is low, but it can also be useful earlier, when symptoms suggest low iron.

Why it happens in midlife

• Heavy or prolonged periods, which are common in perimenopause as cycles become irregular
• Bleeding in the digestive tract from ulcers, inflammatory bowel disease, polyps or colon cancer, sometimes without visible blood
• Regular use of aspirin or anti-inflammatory painkillers
• Poor absorption from celiac disease, Crohn's disease, H. pylori infection or past stomach or weight loss surgery
• Low dietary iron, including plant-based diets without careful planning
• Endurance training, which the NHLBI lists among factors that can affect iron
• Frequent blood donation

Symptoms that can point to low iron

Many people with mild iron deficiency have no symptoms. When symptoms appear, they are often vague and easy to blame on a busy life or on hormones.

• Fatigue and reduced stamina during exercise
• Shortness of breath with effort that used to be easy
• Dizziness or lightheadedness
• Cold hands and feet
• Pale skin
• Restless legs, especially in the evening
• Hair shedding, which can have many other causes as well

Reading the number

Every lab sets its own reference range for ferritin, and the lower limit differs between labs and between men and women. A result at the very bottom of the range, combined with symptoms or a known cause, may be treated differently from the same number in someone with no symptoms.

Ferritin also rises with inflammation, infection and liver disease. That means a normal ferritin can sometimes hide low iron if you are unwell. Clinicians often pair ferritin with other iron tests, such as serum iron and total iron-binding capacity, and with a complete blood count to see the full picture.

Finding the cause comes first

In midlife, unexplained low iron is a reason to look for blood loss. For women with heavy bleeding, that may mean a gynecology evaluation. For men, and for postmenopausal women, it often means checking the digestive tract, because iron deficiency can be the first sign of a bleeding problem there.

Your clinician may also suggest celiac screening if absorption could be the issue, and will review your medicines. Low ferritin and an underactive thyroid can produce similar tiredness, so thyroid tests are often checked alongside.

How iron is usually replaced

Oral iron supplements are the most common treatment. The NHLBI says restoring iron levels often takes three to six months, and IV iron is used for more serious cases or when tablets don't work or aren't absorbed.

Iron supplements commonly cause stomach upset, constipation or nausea. The NIH Office of Dietary Supplements notes they can reduce absorption of levothyroxine, so the two are usually taken at different times. Vitamin C helps absorption of iron from plant foods. Don't take high-dose iron without testing first: people with hemochromatosis, an inherited iron overload condition, should avoid it.

Questions worth asking at your results review

• Is my ferritin low for this lab's range, and how does it compare with any earlier results?
• Is my hemoglobin still normal, or am I already anemic?
• What is the most likely reason my iron is low, and how will we confirm it?
• Do I need a gynecology or gastroenterology referral to look for blood loss?
• Could inflammation be making my ferritin look higher than my true stores?
• If I start iron, which form and schedule should I use, and when will we recheck?

How HealifyMD can help

Ferritin and iron markers can be included in the lab panel your clinician orders. You review results together in an online visit, and your clinician explains whether your level is likely contributing to symptoms. When low iron needs investigation for blood loss, your clinician will recommend in-person follow-up, such as with your primary care doctor, a gynecologist or a gastroenterologist.