What is hemoglobin and how is it formed?

Hemoglobin ("Hb"), also referred to as the blood count, is the iron-rich protein in red blood cells (erythrocytes). Its task is to transport oxygen from the lungs to the body's organs and tissues. Hemoglobin also helps transport carbon dioxide back to the lungs, where it is removed in exhaled air.

To form hemoglobin, the body needs iron as well as vitamins B12 (cobalamin) and B9 (folate), among other nutrients. Some of the iron and vitamins are absorbed from food in the intestine, transported into the blood and then to the bone marrow, where hemoglobin is formed in red blood cells. Iron in old blood cells is recycled in the body when the cells are broken down.

What is a normal hemoglobin (Hb) level?

The blood count, or hemoglobin level, refers to the concentration of hemoglobin in the blood. It is usually measured in grams per liter (g/L). Typical reference ranges are around 130-170 g/L for men and 120-155 g/L for women. Children may have somewhat lower levels depending on age.

What causes high or low hemoglobin levels?

Hemoglobin levels can be affected by several factors. Low levels can result from significant blood loss, for example due to heavy menstruation, serious injury or bleeding from the stomach or intestines. Anemia can also occur because of vitamin or mineral deficiency. A high hemoglobin value means the blood has an increased oxygen-carrying capacity and can be associated with smoking, high altitude or certain diseases that cause the body to produce more red blood cells than normal. Dehydration, for example from low fluid intake, diarrhea and/or vomiting, can temporarily raise the value because the blood becomes more concentrated as fluid content decreases.

Low hemoglobin (Hb)

Low hemoglobin is called anemia and simply means that there are not enough red blood cells or hemoglobin to carry sufficient oxygen. This can lead to fatigue and breathing difficulties depending on the severity of the anemia. Anemia is commonly defined as <120 g/L for women and <130 g/L for men. Hemoglobin can fall for several reasons.

Common causes of low hemoglobin

• low dietary iron intake or reduced iron absorption.
• deficiency of vitamins B12 (cobalamin) and B9 (folate).
• menstrual bleeding
• blood loss from any cause (surgery, stomach ulcers, bleeding hemorrhoids and major bleeding, for example in accidents)
• chronic gastrointestinal diseases such as celiac disease
• cancer
• kidney failure
• incorrect sampling technique

A lower hemoglobin level is often seen during pregnancy, which is a natural consequence of the body adapting to pregnancy. Normally, both plasma volume and the number of red blood cells increase during pregnancy. Because plasma volume increases more than the number of red blood cells, this creates a dilution effect and a lower hemoglobin level. The threshold for what is considered anemia is therefore lower in pregnant women.

Symptoms of anemia

Anemia can present in many different ways. The most common symptoms are:

• fatigue and weakness
• difficulty concentrating
• pale skin
• headache
• dizziness
• ringing in the ears
• palpitations
• shortness of breath, difficulty breathing
• impaired vision
• sleep problems
• menstrual disturbances

When you donate blood, hemoglobin typically falls by around 10 g/L.

High hemoglobin (Hb)

Hemoglobin levels can rise above the normal range for several reasons. Some causes include:

• dehydration, which reduces blood plasma and makes the blood more concentrated
• staying at high altitude, where oxygen levels are lower, causes the body to increase production of blood cells and raises hemoglobin
• smoking
• heart disease
• chronic obstructive pulmonary disease (COPD)
• sleep apnea
• liver or kidney cancer
• Polycythemia vera (a condition that increases the levels of all blood cells)
• Use of anabolic androgenic steroids
• blood doping

Certain medicines, such as diuretics, can also cause hemoglobin levels to rise.

Symptoms of high hemoglobin

In general, a high hemoglobin level does not cause symptoms. However, high hemoglobin can lead to serious and potentially life-threatening complications such as blood clots. How do you check your hemoglobin level?
A hemoglobin test, often called Hb or blood count, is a common part of a health check whether or not disease is suspected. Hemoglobin (Hb) is checked with a standard blood test. With a hemoglobin meter, you can easily measure and monitor your Hb value at home without a doctor's visit or long healthcare queues. This is a convenient solution for anyone who wants to check their blood values regularly.