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.
Key takeaways
Ferritin is the protein that stores iron, so the blood test reflects your iron reserves.
Low ferritin is often the earliest sign of iron deficiency and can bring fatigue, hair shedding and restless legs before anemia appears.
High ferritin may reflect inflammation, liver strain or iron overload, which is why it is read with markers like hs-CRP.
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 of low ferritin include fatigue, pale skin, shortness of breath on exertion, hair loss, restless legs, and poor exercise performance. Common causes include heavy periods, pregnancy, frequent blood donation, endurance training, and low dietary iron.
Absorption problems such as low stomach acid, celiac disease, gut inflammation, and long-term PPI use can also play a part. There is a thyroid link as well, because iron is needed for thyroid hormone production, so low ferritin can affect thyroid function.
What high ferritin can mean
High ferritin can point to hemochromatosis, a genetic iron overload disorder that can affect the liver and heart (HFE gene testing may be considered). It can also reflect chronic inflammation or infection, for example rheumatoid arthritis, or liver conditions such as fatty liver, hepatitis, or alcohol-related damage. Rarely, certain cancers are involved, which is why 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, so please discuss it with your provider rather than self-dosing.
It is also important to investigate the cause, such as heavy periods, gut absorption problems like low stomach acid, celiac disease or SIBO, or training load. 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, and follow an anti-inflammatory eating pattern with less sugar and alcohol and 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.
What does the research show about ferritin?
Using US national survey data from 7,498 non-pregnant women aged 15 to 49 without inflammation or liver problems, researchers looked for the ferritin level below which hemoglobin starts to fall and the iron-hungry marker soluble transferrin receptor starts to rise. Both pointed to a threshold of about 24 to 25 micrograms per liter, well above the long-used cutoff of 15. The analysis was cross-sectional and excluded people with inflammation, so it may not apply when ferritin is raised by illness. (Mei et al., 2021)
A randomized trial in France enrolled 198 women aged 18 to 53 with unexplained fatigue, ferritin below 50 micrograms per liter and normal hemoglobin, and gave 80 mg of elemental iron daily or placebo for 12 weeks. Fatigue scores fell by 47.7% with iron versus 28.8% with placebo, and ferritin rose by 11.4 micrograms per liter more than with placebo, but quality of life, mood and anxiety did not differ. The trial was short, was not fully blinded for participants, and the large placebo response shows how much fatigue can vary. (Vaucher et al., 2012)
The HEIRS study tested 99,711 adults from primary care practices for ferritin, transferrin saturation and the main hemochromatosis gene variant. Among 227 people with two copies of the variant who had not been told they had iron overload, 88% of men had ferritin above 300 and 57% of women had ferritin above 200 micrograms per liter, while 364 people without a known evaluation had ferritin above 1,000. The study was a one-time screen, so it shows how often high iron goes unnoticed rather than who develops complications. (Adams et al., 2005)
These studies show that ferritin has meaning at both ends, and that it reads best alongside a complete blood count, transferrin saturation and a marker of inflammation such as CRP.
When to see a naturopathic doctor
It may be time to see a naturopathic doctor if you have fatigue, hair loss, restless legs or poor exercise tolerance with low or low-normal ferritin, or if your ferritin stays low despite iron-rich eating or supplements. The same is true if your ferritin is high and you want to understand why, or if heavy periods, gut symptoms, or a plant-based diet may be affecting your iron.
See a medical provider promptly for black or bloody stools, very heavy bleeding, chest pain, shortness of breath at rest, or fainting.
Questions to bring to your clinician
These questions can help you get the most out of your next visit.
Is my ferritin in a range that supports energy and hair health, not just above the lab’s lower limit?
How should I read my ferritin alongside the rest of my labs and my symptoms?
How often would it make sense to recheck my ferritin in my situation?
Which daily habits or medications could be influencing my ferritin before we retest?
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
- Adams PC, et al. Hemochromatosis and iron-overload screening in a racially diverse population. N Engl J Med 2005. PMID: 15858186. https://pubmed.ncbi.nlm.nih.gov/15858186/
- Ganz T, et al. Hepcidin and iron homeostasis. Biochim Biophys Acta 2012. PMID: 22306005. https://pubmed.ncbi.nlm.nih.gov/22306005/
- Mei Z, et al. Physiologically based serum ferritin thresholds for iron deficiency in children and non-pregnant women: a US National Health and Nutrition Examination Surveys (NHANES) serial cross-sectional study. Lancet Haematol 2021. PMID: 34329578. https://pubmed.ncbi.nlm.nih.gov/34329578/
- Pfeiffer CM, et al. Laboratory methodologies for indicators of iron status: strengths, limitations, and analytical challenges. Am J Clin Nutr 2017. PMID: 29070545. https://pubmed.ncbi.nlm.nih.gov/29070545/
- Vaucher P, et al. Effect of iron supplementation on fatigue in nonanemic menstruating women with low ferritin: a randomized controlled trial. CMAJ 2012. PMID: 22777991. https://pubmed.ncbi.nlm.nih.gov/22777991/
- Verdon F, et al. Iron supplementation for unexplained fatigue in non-anaemic women: double blind randomised placebo controlled trial. BMJ 2003. PMID: 12763985. https://pubmed.ncbi.nlm.nih.gov/12763985/
- 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.
Free: The 28-Day Reset for Energy and Focus
A simple day-by-day email guide to sleep, movement, food, and daily habits that support healthy aging. It’s free, and you can unsubscribe anytime.
Get the free guide Take the supplement quiz
