Quick answer: Ferritin is the protein that stores iron, and the ferritin blood test reflects your body’s iron reserves. Low ferritin is often the earliest sign of iron deficiency. It can cause fatigue, hair loss, restless legs and poor exercise tolerance even before anemia appears. High ferritin may signal inflammation, liver issues or iron overload, so it is always interpreted alongside other markers like hs-CRP and transferrin saturation.
What is ferritin?
Ferritin works like an iron bank. It stores iron safely, mainly in the liver, spleen and bone marrow, and releases it when your body needs it for hemoglobin, energy production, brain function and muscle health. A small amount circulates in the blood, and that level reflects your iron reserves.
Why ferritin matters
Low ferritin is often the earliest indicator of iron deficiency, before anemia shows up on a CBC. High ferritin may point to inflammation, liver dysfunction, or genetic conditions like hemochromatosis. Because ferritin is an acute phase reactant, it rises during inflammation, infection or stress. It should be read alongside hs-CRP and transferrin saturation.
Normal vs. optimal ferritin ranges
- Standard lab ranges are broad (roughly 15–400 ng/mL depending on lab, sex and age).
- Women: many functional medicine practitioners prefer about 70–100 ng/mL for energy and hormonal health.
- Men: often about 100–150 ng/mL.
- Children: ranges vary by age; consult a pediatric provider.
Always review your results with a healthcare provider. Context, such as inflammation and other iron markers, is critical.
Signs and causes of low ferritin
- Symptoms: fatigue, pale skin, shortness of breath on exertion, hair loss, restless legs, and poor exercise performance
- Common causes: heavy periods, pregnancy, frequent blood donation, endurance training, low dietary iron
- Absorption problems: low stomach acid, celiac disease, gut inflammation, and long-term PPI use
- Thyroid link: iron is needed for thyroid hormone production, so low ferritin can affect thyroid function
What high ferritin can mean
- Hemochromatosis: a genetic iron overload disorder that can affect the liver and heart (HFE gene testing may be considered)
- Chronic inflammation or infection: for example, rheumatoid arthritis
- Liver conditions: fatty liver, hepatitis, or alcohol-related damage
- Rarely, certain cancers: very high ferritin always needs medical follow-up
How iron is absorbed: the short version
Heme iron from animal foods such as beef, liver and poultry is absorbed more efficiently than non-heme iron from plants such as lentils, spinach and fortified cereals. Vitamin C improves non-heme iron absorption, while tea, coffee, calcium and phytates can reduce it. Copper and vitamin A help the body move and use stored iron. The hormone hepcidin regulates absorption: it rises with inflammation and traps iron in storage, which is one reason ferritin can be high while you still feel iron-depleted.
Supporting healthy ferritin levels
If ferritin is low:
- Eat iron-rich foods with a vitamin C source, and keep tea and coffee away from meals
- Ask your provider about a gentle iron form, such as iron bisglycinate. The amount should be based on your labs; please discuss it with your provider rather than self-dosing
- Investigate the cause: heavy periods, gut absorption problems such as low stomach acid, celiac disease or SIBO, or training load
- If you work with me, you can find the iron products I use in my Fullscript dispensary. See also who should consider iron (and who should not)
If ferritin is high:
- Look for inflammation, liver, metabolic or genetic causes with your provider
- Follow an anti-inflammatory eating pattern: less sugar and alcohol, more fatty fish and vegetables
- Do not supplement iron unless your provider advises it
- Blood donation or therapeutic phlebotomy is used for confirmed iron overload, under medical supervision
Labs that give ferritin context
Ferritin is most useful together with serum iron, TIBC, transferrin saturation, a CBC and hs-CRP. Many people retest every 3–6 months while correcting a level.
Low iron is one of the most common hidden drivers of fatigue. Read more in why you may always feel tired.
When to see a naturopathic doctor
- Fatigue, hair loss, restless legs or poor exercise tolerance with low or low-normal ferritin
- Ferritin that stays low despite iron-rich eating or supplements
- High ferritin and you want to understand why
- Heavy periods, gut symptoms, or a plant-based diet that may affect iron
See a medical provider promptly for black or bloody stools, very heavy bleeding, chest pain, shortness of breath at rest, or fainting.
Low energy and wondering about your iron? Let’s look at the whole picture.
A free 15-minute consultation with Dr. Kneessi. No cost, no obligation. In-office in Odenton, MD or by telehealth.
Frequently asked questions
What is a good ferritin level?
Lab reference ranges are wide and differ by lab, sex and age. Many people with fatigue, hair loss or restless legs have ferritin in the low-normal range. In my practice I often like to see ferritin around 50–100 ng/mL or higher for energy, interpreted alongside other iron markers and inflammation.
What causes low ferritin?
Common causes are heavy menstrual periods, pregnancy, frequent blood donation, endurance exercise, low dietary iron, and poor absorption, for example from low stomach acid, celiac disease or long-term PPI use.
What does high ferritin mean?
Ferritin rises with inflammation, infection, fatty liver, heavy alcohol use, and iron overload conditions such as hemochromatosis. Because it is an acute phase reactant, it should be read with hs-CRP and transferrin saturation.
Should I take iron if my ferritin is low?
Only after testing and with a provider’s guidance. Too much iron can be harmful, and the cause of low iron, such as blood loss, should be identified. Gentle forms like iron bisglycinate taken with vitamin C are often used. Keep iron supplements away from children.
How often should ferritin be rechecked?
Usually every few months while correcting a low or high level, then periodically, as your provider recommends.
Sources
- Verdon F, et al. Iron supplementation for unexplained fatigue in non-anaemic women: double blind randomised placebo controlled trial. BMJ 2003. PMID: 12763985. https://pmc.ncbi.nlm.nih.gov/articles/PMC156009/
- Ganz T, Nemeth E. Hepcidin and iron homeostasis. Biochim Biophys Acta 2012. PMID: 22306005. https://pmc.ncbi.nlm.nih.gov/articles/PMC4048856/
- Pfeiffer CM, Looker AC. Laboratory methodologies for indicators of iron status: strengths, limitations, and analytical challenges. Am J Clin Nutr 2017. PMID: 29070545. https://pmc.ncbi.nlm.nih.gov/articles/PMC5701713/
- MedlinePlus: Ferritin Blood Test
- NIH Office of Dietary Supplements: Iron (Consumer Fact Sheet)
- NIH Office of Dietary Supplements: Iron (Health Professional Fact Sheet)
This article is for educational purposes only and is not medical advice. It does not replace an individual evaluation. Talk with your healthcare provider before starting supplements or changing medications, especially if you are pregnant, nursing, or managing a health condition.
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