Understanding Your Iron Group: What Results Mean for Each Biomarker

Demystify your bloodwork, including the puzzling combination of high iron and low ferritin. Learn what each marker means for your overall health

Ashley Reaver
By Ashley Reaver
Jovan Mijailovic
Edited by Jovan Mijailovic

Updated March 22, 2024.

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We're fully committed to providing a complete view of your health and the tools to improve your biomarkers.

This logic extends to the Iron Group, a collection of 11 blood biomarkers that assess different characteristics of your body's iron status, from storage to transport to oxygen-carrying capacity to the size and composition of your red blood cells.

It is the most detailed group we analyze from your blood results, and it isn't very easy. But true to our word, we're here to make it easier for you.

How does iron act in the body?

Iron is a trace mineral—similar to zinc, copper, chromium, selenium, and iodine—that our body needs in small amounts, usually less than 5 grams daily. Although we need little of it, it's anything but unimportant. It forms hemoglobin and myoglobin—proteins found in red blood cells that transport oxygen from the lungs to every cell in the body.

Some other notable functions of iron:

  • It’s required in at least two different steps in energy metabolism, outside of providing the oxygen for the final step.
  • Iron is a cofactor in the production of neurotransmitters, primarily those required for the developing brain of infants and children.
  • This mineral produces natural killer cells to boost the immune system. When iron is low, the likelihood and severity of illness from infection increases.
  • The superfamily of enzyme-collecting, known as Cytochromes P450, also contains iron. It's involved in a range of reactions in the body, including drug and alcohol metabolism, cholesterol synthesis, sex hormone production, and the metabolism of vitamin D.

Note: With all these essential functions, it is no wonder that people with low iron lack energy and feel lightheaded and foggy. Next, we'll break down all of the InsideTracker's iron group markers and explain their significance to your health.

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Ferritin: stores iron and reveals its status

Ferritin is a protein that stores iron. It is found in the intestinal cells, which are responsible for absorbing this mineral from the diet and pushing it into the bloodstream. The more iron-rich foods you eat, the higher it becomes.

Since intestinal cells have roughly a 2-5-day lifespan, they eventually get discarded. They also excrete the iron trapped inside, which ensures the mineral's levels don't go too high.

How high dietary iron increases ferritin

Ferritin binds to iron in the blood and releases it whenever the cells need it. It does so even if there isn't an excess of the mineral in your system—almost like a magnet.

The system of trapping iron in intestinal cells isn’t iron-clad. If there's too much of it, the mineral eventually overloads the storage protein and enters the blood. The process results in higher levels of ferritin, increasing the risk of iron deposits in the brain, organs, joints, and muscles—including the heart.

Note: Excess dietary iron intake can also be deposited in the pancreas, impacting its ability to excrete insulin and control blood glucose levels. This process is one reason why high red meat intake is believed to be linked to a higher risk of developing diabetes.

» Explore the relationship between iron, ferritin, and restless leg syndrome

Ferritin helps fight inflammation

The body sequesters iron from the blood into ferritin when bacteria and viruses enter the bloodstream. These foreign invaders can't infiltrate the storage protein because they need the mineral to propagate, and their growth and assault on the body stop.

Note: If you have an elevated ferritin level and high hs-CRP, your ferritin is likely falsely elevated due to inflammation.


This genetic condition causes the body to absorb too much iron from the small intestines. It breaks the mechanism that regulates the mineral's absorption, which prevents your system from getting rid of the excess iron.

A person can carry the genetic trait from one or both parents. And we’ve had a surprising number of InsideTracker users discover they have it because of high ferritin levels.

High ferritin is considered greater than 200 ng/mL in women and more than 300 ng/mL in men. To decrease levels, reduce dietary iron and consider donating blood regularly, especially if you're a man.

How low dietary iron decreases ferritin

Ferritin is a relatively consistent measure of iron status, unlike other markers like serum iron. It won't change based on one meal or supplement because it has to do with the long-term status of the mineral—sometimes, this protein doesn't change for weeks or months.

When dietary iron is low, the body doesn't store it as much. There's now less ferritin in the intestinal cells to prevent the mineral from being trapped and lost. Low ferritin levels are often the first signs of developing anemia.

The body's high iron requirement makes maintaining storage easier if you take enough consistently. It also absorbs the mineral faster when needed and slower when it's not, similar to the law of diminishing returns. Here's when your ferritin levels are too low:

WomenLess than 11ng/mL
MenLess than 25/ng/mL
Active individuals of both sexesLess than 30/ng/mL
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Hemoglobin: helps red blood cells transport oxygen

Hemoglobin is a protein that helps the red blood cells pick up oxygen from the lungs and transfer it around the body. Each of its molecules has iron in the center, which allows it to move four bits of oxygen. When the mineral is low, the carrying capacity of the hemoglobin is reduced.

Did you know?

Red blood cells and hemoglobin are made in the bone marrow and are found inside long bones like the femur in the thigh and flat bones like those in the hips.

What causes high hemoglobin?

  • High altitudes: At elevation, oxygen concentration in the air is sparse. The body responds by producing more red blood cells and hemoglobin to better transport oxygen.
  • Medication: Some medications, like erythropoietin (EPO)—the drug that eventually busted Lance Armstrong for doping—increase red blood cell production.
  • Polycythemia: A condition classified by the high production of red blood cells, which can also cause high hemoglobin levels.
  • Dehydration: Hemoglobin is measured as a concentration. If your blood volume is low, its levels can appear falsely high.

How low ferritin decreases hemoglobin

Low hemoglobin is often the result of decreased ferritin. It signifies inadequate iron in your diet, but only when your inflammation levels are under control. If so, you should take more of the mineral through your diet.

Effects of a new workout routine

One of the body’s first responses to a new workout routine is to produce more blood faster to meet the rising demands for fuel and oxygen throughout the body. Red blood cell production and hemoglobin catch up but can initially appear low.

» Avoid the crash and monitor your iron status to save your session

Seasonal changes influence hemoglobin

The cardiovascular system diverts blood to the skin to release heat when body temperature rises during summer. The blood volume increases to pump it to the skin's surface, and hemoglobin concentration stays diluted for some time.

Did you know?

One of the first responses to pregnancy in a woman’s body is increasing blood volume, dramatically lowering measured hemoglobin concentration. This is normal, although levels remain less than normal for most.

Overhydration upsets blood volume levels

Overhydration before a blood draw can increase the amount of water in the sample, which lowers hemoglobin levels. In this case, there's nothing you'd be able to do other than acknowledge the context of the results.

Since hemoglobin is measured per deciliter of blood, optimal ferritin levels and low inflammation can determine the change in blood volume as the cause of its low levels.

» Learn how to optimize your iron levels for maximum endurance and energy

Do genetic predispositions cause low hemoglobin?

Some genetic predispositions can result in lower levels of hemoglobin. [1] Sickle cell anemia is a mutation that causes C-shaped red blood cells. It decreases the amount of this protein the red blood cells may transport. And while an individual with it is likely aware, less-obvious conditions may be the culprit.

Thalassemia, a family of mutations that decreases hemoglobin production, can have mild to severe effects. People of Mediterranean, Middle Eastern, and Northern African descent are more likely to experience it. Both of these diseases provide some resistance against malaria, which is why they are more common in areas where malaria exists.

Lastly, low hemoglobin can result from deficiency anemia caused by lacking other micronutrients like folate or vitamin B12, which are necessary to produce red blood cells. In such cases, testing and correcting micronutrient deficiencies is essential for restoring the protein's levels.

Serum iron: a short-term measure of status

Serum iron measures this mineral in your blood during the blood test. This metric is often less informative than ferritin for overall iron metabolism.

What causes high serum iron?

Supplements like multivitamins and fortified foods such as cereals and protein powders can raise serum iron levels. Consider removing one if you regularly take multiple of them through your diet.

In severe cases, high serum iron can also result from liver diseases or hemolytic anemia. This condition destroys red blood cells fast, and the body can't produce enough to catch up. It ruptures the red blood cells and spills their contents— including— into the blood.

Causes of low serum iron

  • Low dietary iron intake.
  • Inflammation occurs when the body is infected. It protects itself by removing free iron from the blood and binding it to ferritin, where invaders can't access it.
a picture of a plate of food and a picture of a bowl of food

» Don't be fooled by labels. Learn the truth about iron absorption

Transferrin saturation (TS): indicates iron transport around the body

Once iron passes from the intestinal cell to the blood, it becomes transferrin. The protein shuttles around the body and distributes the mineral to cells. Tests measure TS as a percentage, which shows how much serum is bound to the transporter molecule.

What causes high TS?

High levels of transferrin saturation typically result from increased serum iron. This means there's a high percentage of available transport spots filled with iron.

It’s easy to visualize this process as a bus. It functions best when it's only about 20-50% full. Above 50% can indicate iron overload, which, similar to serum iron, can be due to just one meal or supplement.

What causes low TS?

TS of less than 20% indicates low iron and a possible risk of anemia. The liver produces more transferrin to increase the mineral's transport to cells.

But with low amounts of serum iron, we’ll find a low TS—a more significant percentage of empty seats on the bus. Just like low levels of serum iron, it can happen because of high inflammation.

Total iron binding capacity (TIBC)

Total iron-binding capacity is an inverse measurement of transferrin. It will be high when saturation (%) is low. High levels of TIBC indicate a low amount of iron “filling seats” on the bus we discussed. It's one way to tell if the protein's levels are elevated due to inflammation.

What causes high RBC?

High red blood cells are linked to elevated hemoglobin and hematocrit in polycythemia. It may result from high altitude, decreased oxygen concentrations in the blood, or genetic factors. Reduced blood volume or dehydration can also cause it.

What causes low RBC?

The body needs enough specific vitamins and minerals, especially vitamin B12, folate, and iron, to make healthy red blood cells. These nutrients help your bone marrow produce enough red blood cells.

Due to bone marrow, kidney, or liver disease, hemolysis can destroy RBCs faster than your body can make them. It's often a sign of anemia.

A diagram explaining hemoglobin.


The hematocrit test measures the percentage of red blood cells in your blood. During this test, blood is centrifuged—spun at high speed—to separate the RBCs from the liquid portion—plasma.

Note: Hematocrit, hemoglobin, and red blood cell count are often interrelated. They tend to be all normal, high, or low together—reflecting the overall number of RBCs.

Red blood cell distribution width (RDW)

Red blood cells typically have a similar size and shape. The RDW test measures how much this size varies. Ideally, red blood cells should be uniform.

A high RDW indicates a more considerable difference in red blood cell sizes. This can happen when immature red blood cells are released prematurely due to nutrient deficiencies, affecting their size consistency.

Mean corpuscular volume (MCV)

The mean corpuscular volume (MCV) test measures the average size of your red blood cells.

  • Large red blood cells (high MCV): This is called macrocytosis. It often happens when immature, larger red blood cells are released early due to vitamin B12 or folate deficiencies. Correcting the deficiency can help normalize MCV.
  • Small red blood cells (low MCV): This is called microcytosis. It can be caused by iron deficiency, insufficient minerals to build healthy red blood cells or excessive blood loss.

» Check out the many biomarkers InsideTracker measures

Mean corpuscular hemoglobin (MCH)

Mean corpuscular hemoglobin (MCH) measures the average amount of hemoglobin in a single red blood cell.

  • High MCH: This can occur with macrocytic anemia, where huge red blood cells are produced due to vitamin B12 or folate deficiencies. These more giant cells can hold more hemoglobin.
  • Low MCH: This can indicate iron deficiency anemia or microcytic anemia. In these cases, there's less hemoglobin available, and red blood cells are smaller, resulting in a lower average amount of hemoglobin per cell.

Mean corpuscular hemoglobin concentration (MCHC)

MCHC is similar to MCH, but instead of measuring the total amount of hemoglobin per red blood cell, it focuses on the hemoglobin concentration within the cell itself.

  • Low MCHC: This is typically seen in microcytic or iron deficiency anemia. In these cases, red blood cells are smaller and may not contain enough hemoglobin, leading to a lower concentration.
  • High MCHC: While a high MCHC can suggest an increased need for hemoglobin or oxygen, it's not as straightforward. It's primarily seen in smokers, but other conditions can also cause it.

3 groups of people most at risk for iron deficiency

1. Premenopausal females

Premenopausal women are especially prone to iron deficiency due to regular blood loss during menstruation. Compared to men, they need more than double the daily recommended intake—18mg vs. 8mg. It's because they're constantly replenishing stores lost through menstruation.

Iron needs also increase significantly during pregnancy—28mg per day—to support the mother's and developing baby's rapid growth. After menopause, women's iron requirements typically return to the same level as men, who need 8mg.

2. Vegans and vegetarians

As you may imagine, vegans and vegetarians who don't eat red meat at all are at a greater risk of iron deficiency. While it's not the only source of iron in the diet, it's the most significant, readily available, and readily consumed in the US.

3. Endurance athletes

Another factor that can further increase iron needs is endurance activity. Heel strike—when the foot hits the road during activities like running—causes red blood cells flowing through capillaries to rupture, leading to more iron loss.

A picture of a variety of foods.

How to get enough dietary iron

Plant-based diets can be rich in iron sources like spinach and beans, but our bodies struggle to absorb much of it. This is due to two factors:

  • Anti-nutrients: Plant foods contain compounds like phytates—in grains and legumes—and oxalates (in spinach) that hinder iron absorption.
  • Iron form: Plant iron (Fe3+) must be converted to the more absorbable form (Fe2+) in the small intestine, reducing overall bioavailability.

Some of the best dietary sources of iron are:

  • Red meat
  • Mollusks
  • Clams
  • Mussels
  • Oysters
  • Octopus
  • Whelk

Note: To find out the status of your iron group and the best foods to improve your iron based on your preferences, it’s best to get a comprehensive blood test every few months.

» Learn the difference between heme and non-heme iron

Take control of your iron health

Interpreting an iron group panel can feel overwhelming, but by understanding each biomarker's role, you gain valuable insight into your iron status. If your results raise any concerns, don't hesitate to discuss them with your doctor.

They can use your iron panel results along with your medical history and symptoms to determine if further investigation or treatment is necessary.

InsideTracker's Ultimate plan can also analyze your bloodwork, including iron panels. Based on the results you'll see where you're optimized and what needs work. The personalized recommendations for diet and exercise will also help you improve your levels to live healthier and longer.

Disclaimer: InsideTracker doesn't diagnose or treat medical conditions. Consult your physician for any health concerns


[1] Weatherall D, Akinyanju O, Fucharoen S, et al. Inherited Disorders of Hemoglobin. In: Jamison DT, Breman JG, Measham AR, et al., editors. Disease Control Priorities in Developing Countries. 2nd edition. Washington (DC): The International Bank for Reconstruction and Development / The World Bank; 2006. Chapter 34.Available from: https://www.ncbi.nlm.nih.gov/books/NBK11727/ Co-published by Oxford University Press, New York