Factors That Affect Hemoglobin Levels and Overall Blood Function

Originally Medically Reviewed by Dr. Sony Sherpa, (MBBS) - June 15, 2022

Fact Checked and Updated by Dr. Asif Baliyan, MD - June 04, 2026

What Is Hemoglobin?

Hemoglobin is a protein found on the inside of the red blood cells (RBCs) of animals and humans. It is responsible for transporting oxygen to the tissues where it is required.

Each hemoglobin molecule comprises 4 subunits. Each of these units has an iron-containing compound known as heme and a protein chain (called the globin), which together form the hemoglobin. When hemoglobin combines with an oxygen molecule, it appears bright red and is called oxyhemoglobin, whereas in the absence of oxygen, it appears purple-blue and is called deoxyhemoglobin.

Hemoglobin develops in the bone marrow, the soft and spongy tissue found in the center of most bones. The RBCs have a life span of approximately 110 to 120 days, after which they die. When this happens, the hemoglobin is broken up. The iron and the protein obtained are recycled, whereas the remaining constituents are excreted.

A person’s hemoglobin levels determine the amount of protein in the blood. If your hemoglobin levels are either too high or too low, this can lead to a host of consequences for your health. The amount of hemoglobin is expressed in grams per deciliter (g/dL) of whole blood.

Normal hemoglobin levels depend on many factors, such as age and gender. Generally, for adult males, it is 14 to 18 gm/dL, whereas for females it is 12 to 16 g/dL. It is relatively uncommon to have high hemoglobin levels.

Elevated hemoglobin is a consequence of having too many RBCs, a condition called erythrocytosis. Anemia is a condition in which your hemoglobin is below the normal reference range for your age and gender.

What is hematocrit?

Hematocrit is the volume of RBCs compared to the total blood volume, which comprises both RBCs and the liquid component (plasma). The normal hematocrit for men is 40 to 54%; for women, it is 36 to 48%.

What Affects Hemoglobin Levels?

Several factors affect the levels of hemoglobin in the body. Let’s take a look at some of these factors:

Age

The normal hemoglobin is different for infants, children, and adults. Given below are the normal hemoglobin levels according to age:

• Newborn: 14-24 g/dL
• 0-2 weeks: 12-20 g/dL
• 2-6 months: 10-17 g/dL
• 6 months-1 year: 9.5-14 g/dL
• 1-6 years: 9.5-14 g/dL
• 6-18 years: 10-15.5 g/dL
• Older adults: Slight decrease in values

Newborns have higher hemoglobin concentrations than adults primarily because fetal erythropoiesis occurs in a relatively hypoxic intrauterine environment, which stimulates erythropoietin production and increases red cell mass. Fetal hemoglobin possesses a higher oxygen affinity than adult hemoglobin, facilitating placental oxygen uptake. Although HbF releases oxygen less readily to tissues than HbA, the elevated hemoglobin concentration and specialized fetal circulatory adaptations ensure adequate tissue oxygen delivery during fetal life.

Older adults have slightly lower levels of hemoglobin. This could be due to blood loss or chronic diseases that lead to anemia. Sometimes, comorbid conditions even mask the symptoms of anemia.

Race

Hemoglobin levels in black people are consistently lower than in the white population. The ethnic differences in hemoglobin levels may be a consequence of a combination of overall nutrition, iron status, and inflammation in the body.

Additionally, several genetic disorders affecting the RBCs, like sickle cell disease, are more commonly found in Africa, South America, India, and Mediterranean countries.

Gender

Men have increased hemoglobin levels compared to women. The male hormone, testosterone, has a stimulatory effect on the bone marrow, leading to the production of more RBCs and hemoglobin.

Diet

Can a poor diet cause anemia?

A diet that lacks iron is a leading cause of anemia. Iron is needed to form hemoglobin, and its deficiency can hamper the production of RBCs.

Consuming foods that are rich in iron, like red meat, poultry, seafood, dark leafy vegetables, and iron-fortified cereals, helps increase iron in the blood.

Vitamin C helps the body absorb iron more readily. Eat more citrus fruits, bell peppers, and berries as they are rich in vitamin C.

Folic acid is another B-complex vitamin needed to make RBCs. Green leafy vegetables, dried beans, sprouts, peanuts, broccoli, and bananas are some folate-rich foods.

There is no single best diet for anemia. Eating a balanced, healthy diet can help you get all the essential nutrients to increase hemoglobin.

Altitude

The amount of hemoglobin in the blood increases in people residing at higher altitudes.

There is decreased oxygen availability at high altitudes. The body adapts to lower oxygen pressure by increasing red blood cell production and hemoglobin concentration, improving the blood’s oxygen-carrying capacity.

For this reason, some athletes deliberately train at high altitudes. This increases their hemoglobin levels and improves performance. Three weeks of traditional altitude training at 2,050 meters increases red blood cell production even in world-class endurance athletes.

Physical Activity

Hemoglobin and regular physical activity are interconnected. Exercise can increase hemoglobin and red blood cell mass.

But why does exercise increase hemoglobin? Additionally, do athletes have high hemoglobin levels?

During exercise and physical activity, the body needs more oxygen than during usual daily activities. All the oxygen needed in the muscles is obtained from the bloodstream.

To physiologically adjust to the demands of increased activity, red cell production increases. Higher hemoglobin levels can increase the blood’s oxygen-carrying capacity and may support endurance performance. However, athletic performance depends on multiple physiological factors, and most trained athletes do not develop true erythrocytosis. In fact, endurance training often results in plasma volume expansion, which may lead to a dilutional decrease in hemoglobin concentration known as ‘sports anemia’.

Hydration

How can dehydration cause anemia?

Hemoglobin and hematocrit are measured based on whole blood, which is dependent on the fluid component called plasma.

Here is how dehydration and hemoglobin levels are interlinked.

If a person is severely dehydrated, the plasma volume decreases. Consequently, hemoglobin and hematocrit will appear higher than if the patient had normal plasma due to adequate hydration. Acute dehydration can raise the hemoglobin concentration by as much as 10 to 15%.

Likewise, in case of fluid overload, hemoglobin and hematocrit will be lower than their actual level due to dilution.

Smoking

Why do smokers have high hemoglobin?

Carbon monoxide, a component of cigarette smoke, binds hemoglobin with an affinity that is 200 times greater than oxygen. This carboxyhemoglobin does not allow oxygen to bind to hemoglobin, causing a state of low tissue oxygen (hypoxia). The body then detects hypoxia and stimulates the bone marrow to produce more RBCs as a compensatory response.

Medication

Certain medications cause anemia by triggering the body's defense or immune system to attack its red blood cells. This causes red blood cells to break down earlier than normal, in a process called hemolysis.

Can antibiotics lower your hemoglobin?

Cephalosporins (a class of antibiotics) are the most common medication that can cause this type of hemolytic anemia. Other antibiotics with similar effects are Dapsone, Levofloxacin, Nitrofurantoin, and Penicillin.

Related: 10+ Supplements That Can Affect Blood Clotting

Menstruation

Can heavy periods cause anemia?

When you lose a lot of blood during your period, you may end up losing more red blood cells than your body can make. This can also reduce the amount of iron in your body. As a result, your body will have a harder time making hemoglobin.

Posture

A change in posture from lying down on your back to sitting upright can cause elevated hemoglobin and hematocrit. Furthermore, a change of posture from sitting to standing can result in similar effects.

The changes in hemoglobin levels have been attributed to alterations in plasma volume. Posture changes cause fluid to move in and out of the blood vessels, thereby affecting the hemoglobin concentration.

Blood Diseases

Many blood disorders can influence hemoglobin levels.

For instance, Polycythemia vera is a type of blood cancer that causes your bone marrow to make too many red blood cells. It is caused by a genetic mutation.

Similarly, Thalassemia and Sickle cell disease are inherited blood diseases in which the body makes abnormal hemoglobin.

Tumors of the bone marrow, such as leukemia, lymphomas, multiple myeloma, and myelodysplastic syndrome, impair the production of normal RBCs, causing a drop in hemoglobin levels.

Pregnancy

During pregnancy, the amount of blood produced by the body increases by up to 30%. The body requires more iron to produce sufficient hemoglobin, which will otherwise lead to anemia.

Another reason for reduced hemoglobin in pregnancy is the increased blood volume and subsequent dilution of RBCs.

According to WHO guidelines, hemoglobin levels below 11 g/dL during pregnancy are considered diagnostic of anemia.

Acute Blood Loss

Losing large amounts of blood in a short time will decrease hemoglobin levels.

The loss of red blood cells exceeds the production of new red blood cells, resulting in anemia. The body also quickly pulls water from tissues outside the bloodstream in an attempt to keep the blood vessels filled. As a result, the blood is diluted, and the hematocrit is reduced.

Some causes of acute blood loss are road traffic accidents, massive bleeding from the digestive system, ruptured blood vessels, surgery, childbirth, and disseminated intravascular coagulation (DIC).

Chronic Disease

Elevations in hemoglobin and hematocrit levels can be caused by a chronic decrease in plasma volume, which is termed stress erythrocytosis. It can be seen if there is a long-term increase in blood pressure in overweight, and middle-aged men.

When you have an autoimmune disease or an illness lasting longer than 3 months, your hemoglobin falls, leading to a condition known as Anemia of Chronic Disease.

It may be seen in conditions that cause inflammation, such as infections, cancer, and chronic kidney disease. The inflammation may prevent your body from using stored iron to make enough healthy red blood cells, leading to decreased hemoglobin levels.

Diseases and tumors of the kidney can also cause the hemoglobin levels to fall. The kidney secretes erythropoietin (EPO), a protein that stimulates the bone marrow to produce more red cells. When your kidneys cannot make EPO, anemia develops.

An enlarged spleen is another condition that can decrease hemoglobin. Your spleen filters RBCs as they move through your body. It traps and destroys damaged or dying red blood cells.

When the spleen enlarges, as in some diseases, it traps more red blood cells than usual, essentially ending those cells’ lifespan earlier than usual.

What Happens When Hemoglobin Levels Are Altered?

Low hemoglobin levels make you very tired and listless as the cells in your body aren’t getting enough oxygen. It can also cause pale or yellowish skin, shortness of breath, and irregular heartbeat.

Higher-than-normal hemoglobin levels can cause headaches, blurred vision, dizziness, red skin on the face, hands, and feet, confusion, and discomfort in your tummy.

How to Know Your Hemoglobin Levels

Hemoglobin is measured as part of a routine blood test known as a Complete Blood Count (CBC).

To carry out a CBC, a blood sample is typically taken from the veins of your arms. Alternatively, a member of your health care team can prick your fingertips and take a blood sample. For infants, the sample may be obtained by pricking the heels.

The sample is then sent to the laboratory for analysis. You can resume normal activities right after the procedure.

The Bottom Line

The hemoglobin count is an indirect measurement of the number of red blood cells in your body. Many factors can alter this level, and both anemia and erythrocytosis can have a detrimental effect on health. Identifying the factors that affect hemoglobin levels can help you get the required treatment before it is too late.

FAQ

What foods should you avoid if you have low hemoglobin?

Avoid foods that interfere with iron absorption, such as tea and coffee, milk and some dairy products, and those that contain tannins, such as corn, grapes, and sorghum. Other foods to avoid are those that contain oxalic acids, such as parsley, peanuts, and chocolate, and foods with phytates or phytic acids, such as whole-grain wheat products and brown rice.

Can exercise cause anemia?

Some high-intensity and endurance types of exercise may cause anemia by increasing iron losses by as much as 70%. This can be due to heavy sweating or blood loss in the urine and from the digestive tract.

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