Hemoglobin Levels: High, Low and Normal Range: The Complete Guide

Hemoglobin (Hgb or Hb) is a protein found in red blood cells which is required to transport oxygen throughout the body. Your blood needs hemoglobin levels to be in the normal range to provide oxygen to the cells in your body. Low hemoglobin levels result in various types of anemia which can cause symptoms like fatigue, dizziness, headaches, and shortness of breath. High levels of hemoglobin are less common and can also result in similar symptoms to low hemoglobin in the blood.

Vitamin and mineral deficiencies in your diet, blood loss, thyroid disorders, and pregnancy are some of the causes of low hemoglobin levels and anemia. In order to treat abnormally low hemoglobin levels, you’ll need to know the type of anemia you have and what caused it. Very often, iron or vitamin B12 supplements help to increase hemoglobin levels in the blood.

In this article, I will look at the medical reasons why hemoglobin levels in your blood can be below or above the normal range. You will also find out how to increase low hemoglobin levels with diet or by taking supplements.

What Is Hemoglobin (Hgb or Hb)?

Hemoglobin (Hgb or Hb) is a protein found in red blood cells that is responsible for carrying oxygen around the body.

Doctors on MedicineNet say that each hemoglobin molecule contains iron compounds that also give blood its distinct red color. When red blood cells die off, the iron gets absorbed into the bone marrow and helps to produce new red blood cells (RBCs). Leftover hemoglobin turns into bilirubin and goes into the digestive bile. This is the chemical that is responsible for the color of your stool.1

What Is a Hemoglobin Test?

A hemoglobin test measures the levels of hemoglobin in your blood. This blood test is usually done as part of a complete blood count test which checks your red blood cell (RBC) indices.

Testing for levels of hemoglobin is usually done if a person shows signs of anemia. If the hemoglobin test shows low hemoglobin levels, doctors may arrange more specific red blood cell tests to determine the exact type of anemia.

Hemoglobin test is also frequently performed with hematocrit (Hct) blood test, which measure the proportion of red blood cells in the blood’s volume.2

Normal Hemoglobin Levels in Males and Females

Labs test results to determine high or low levels of hemoglobin measure hemoglobin level in grams per deciliter (g/dL).

Dr. Brian Yang Merritt, a specialist in hematopathology, says that normal levels of hemoglobin for males and females are as follows:3

  • Normal hemoglobin levels for men: 14.0 – 17.5 g/dL (average is 15.7 g/dL)
  • Normal hemoglobin levels of women: 12.3 – 15.3 g/dL (average is 13.8 g/dL)

Other lab tests results may have a slightly different normal range for hemoglobin levels. For example, Dr. Abimola Farinde on Medscape says that normal hemoglobin levels for men could be as low as 13.0 g/dL.4

Normal Hgb levels also depend on the age of a person. For example, babies under a week old will have normal hemoglobin levels of between 16.5 g/dL and 18.5 g/dL. However, normal levels of hemoglobin in children will drop to around 12.5 g/dL between the ages of 2 and 6. Between the ages of 12 and 18, the hemoglobin levels of teenagers are similar to that of adults.3

Hemoglobin Levels Chart

Below you can see a hemoglobin levels chart with more detailed information on the normal hemoglobin range for adults, children, and babies.

hemoglobin levels chart

Low Hemoglobin Levels

Low hemoglobin levels are defined as values of less than 13.0 g/dL in men and less than 12.0 g/dL in women.5

Low hemoglobin count could be associated with a disease or medical condition. Low hemoglobin levels result in anemia which means that not enough oxygen is getting pumped around your body.

Dangerously Low Hemoglobin Levels

Some people show signs of hemoglobin levels that are dangerously low. The causes of low hemoglobin that can put your life at risk could be due to heavy blood loss, RBCs getting destroyed too quickly, or major problems in your organs.

The journal Critical Care reports that critically low levels of hemoglobin are generally classed as anything below 8 g/dL or 8.5 g/dL.

When hemoglobin levels fall so low, doctors may have to put off surgery and raise hemoglobin levels. In critical cases, doctors may have to order a blood transfusion to increase levels of hemoglobin.7

However, some doctors say that, in some cases, the trigger point for a blood transfusion could be a low as 7.0 g/dL.

Low Hemoglobin Symptoms

You may not always show symptoms of low hemoglobin. In fact, the National Heart, Lung, and Blood Institute says that mild or moderate iron-deficiency anemia may not show any symptoms at all. Usually, symptoms will get worse as hemoglobin levels drop further.8

According to doctors from the Cleveland Clinic, some of the common symptoms of being anemic can include:9

Low Hemoglobin Causes

Let’s look in more detail at what can be causing symptoms of anemia and your hemoglobin levels to drop below the normal range.

Iron deficiency

Iron-deficiency can cause anemia which means that your hemoglobin levels are low. Anemia caused by a lack of iron is called iron deficiency anemia. It occurs when the body can’t store enough iron or when iron is lacking in the diet.

According to researchers from the National Institutes of Health, low hemoglobin and iron-deficiency anemia can develop slowly over time. A lack of iron in your body causes a slowdown in the production of red blood cells. Eventually, you will feel fatigued, out of breath, and suffer from pain in your chest.10

Vitamin B12 deficiency anemia

Not getting enough vitamin B12 or folate in your diet can cause a type of anemia called megaloblastic anemia.

The journal Medical Clinics of North America reported that various gastrointestinal problems can prevent vitamin B12 and folate absorption. This can lead to symptoms like jaundice, fatigue and certain neurological conditions.11

Other reasons for malabsorption and a lack of vitamin B12 can be due to inflammatory bowel disorder (IBD), gastric surgery, or being infected with a tapeworm. Vitamin B12 malabsorption can lead to pernicious anemia.

According to Dr. Neha Pathak on WebMD, a vitamin B12 deficiency anemia can develop if you don’t get enough B12 from your diet. Foods like eggs, meat, and milk contain good levels of vitamin B12 and can help to fortify your blood and prevent anemia.12

Vitamin or mineral deficiency

Anemia can occur if you have vitamin deficiencies, not just vitamin B group deficiencies. Some of the vitamin and mineral deficiencies that can lead to low hemoglobin levels can include any of the following:

Vitamin A. Vitamin A is essential to help store iron in the body. The journal BMC Pediatrics reported that a high vitamin A dose can help raise hemoglobin levels in children and treat some forms of anemia.13

Vitamin D. According to scientific research published in the journal Renal Failure, a lack of vitamin D can lead to anemia and a low hemoglobin count. Vitamin D deficiencies can also cause headaches, tiredness, and back pain.

Zinc. Iron-deficiency anemia can also be linked to a lack of zinc. The journal Annals of Hematology reported that zinc is an important mineral to keep the immune system healthy and keep cells functioning properly. People with low levels of zinc often have below normal levels of hemoglobin.14

Copper. A report published in the International Journal of Surgery Case Reports found that copper is linked to anemia and a low white blood cell count. Doctors say that anemia from a copper deficiency can be hard to detect.15

Anemia during pregnancy

Pregnancy-related anemia is very common due to a decrease in the percentage of hemoglobin molecules in red blood cells and the extra demand for iron.

OB/GYN Dr. Fidelma B. Rigby says that even though there are more red blood cells being produced, low hemoglobin levels can still develop during pregnancy. Iron-deficiency anemia develops as plasma volume increases and the concentration of hemoglobin (hematocrit) becomes lower than normal. Low hemoglobin levels during pregnancy are as follows:16

  • First trimester: below 11 g/dL
  • Second trimester: below 10.5 g/dL
  • Third trimester: less than 11 g/dL hemoglobin levels

If there is a drop in the mean corpuscular volume (MCV) of below 80 fL, this could lead to microcytic anemia. A low hemoglobin count with high MCV (of over 100 fL) can lead to vitamin B12-deficiency anemia or folic acid deficiency anemia.

Anemia during pregnancy is usually treated by taking folate and iron supplements.

Blood loss

Low hemoglobin levels could happen because of chronic blood loss or acute blood loss.

According to the journal Biomedical Reports, upper gastrointestinal bleeding can result in a low hemoglobin count. Bleeding in the stomach or gastrointestinal tract often happen because of ulcers. Other symptoms of gastrointestinal bleeding are passing tarry black stool, burning sensation in your stomach after eating, and pain below the ribs.17

Blood loss during surgery or childbirth can cause a sudden drop in your hemoglobin levels that may become dangerous.18


If your thyroid doesn’t function properly, you may have persistently low hemoglobin levels and symptoms of anemia.

An underactive thyroid doesn’t produce enough thyroid hormone and can lead to a number of anemic-like symptoms. However, according to the journal ISRN Endocrinology, hypothyroidism also causes hemoglobin levels to drop. Blood tests to check for thyroid function and the health of red blood cells show a slight decrease in hemoglobin levels.19

Inflammatory bowel disease (IBD)

Because inflammatory bowel conditions affect the absorption of iron, diseases like ulcerative colitis and Crohn’s disease can cause a drop in hemoglobin (Hgb) levels.

The World Journal of Gastrointestinal Pathophysiology reported that iron deficiency anemia is often a complication of IBD. Inflammation can prevent important vitamins and minerals from being absorbed. Apart from causing digestive problems, IBD can lead to fatigue, weakness, pale skin, and other symptoms of anemia.20

Rheumatoid arthritis

Rheumatoid arthritis is an autoimmune condition that can cause below normal hemoglobin levels and painful joints.

The journal Clinical and Experimental Rheumatology reported that rheumatoid arthritis sufferers often have hemoglobin levels below the normal range. The low hemoglobin (Hgb) levels are sometimes difficult to increase to normal levels if there is a history of gastrointestinal problems, diabetes, or cardiovascular issues.21

It’s important to note that a vitamin D deficiency is also associated with arthritis. For more information on how to manage arthritis symptoms, please read my article on foods to eat and to avoid if you have arthritis.

Kidney disease

Your kidneys that are located in your middle back play an important role in producing enough red blood cells to carry oxygen throughout your body.

The National Institute of Diabetes and Digestive and Kidney Diseases reports that chronic kidney disease often leads to anemia. Kidney dysfunction can cause iron-deficiency anemia or vitamin B12 deficiency anemia. This happens because the kidneys produce a hormone called erythropoietin (EPO) that stimulates the production of oxygen-rich RBCs.22

If you have high blood pressure or diabetes, then you have a greater risk of developing kidney disease. It’s important to drink enough water daily to help flush toxins from your urinary system.

Stomach ulcers (H. pylori infection)

A bacterial infection in your stomach caused by the H. pylori strain can cause stomach ulcers that can cause low hemoglobin.

Doctors from the Mayo Clinic say that, if left untreated, a complication of peptic ulcers is internal bleeding. The chronic blood loss can cause hemoglobin levels to drop to dangerously low Hb levels and cause severe anemia. In severe cases, treatment in hospital is necessary to raise lowered hemoglobin levels.23

You can use Manuka honey as a natural antibiotic to help kill off H. pylori infections that lead to peptic ulcers. You can also check out my other great natural cures for stomach ulcers if you have these gastrointestinal sores.


One of the results of getting old is showing symptoms of anemia because of low hemoglobin levels.

The Journal of the American Geriatrics Society reported that the aging process causes a decline in hemoglobin levels. This brings with it anemia that can greatly impact the quality of life in older persons. Other medical conditions that cause anemia can also affect the elderly and cause hemoglobin levels to fall.24

Blood disorders

Certain disorders of the blood can cause chronic anemia because it’s difficult for hemoglobin levels to rise in order to be within the normal range.

Thalassemia. Doctors from the Mayo Clinic say that thalassemia is a genetic blood disorder that causes symptoms of anemia. Thalassemia causes too few red blood cells and low hemoglobin in males and females. In severe cases, hemoglobin can drop to dangerously low levels below 8g/dL and may require medical intervention to bring up hemoglobin.25

Sickle cell anemia. A blood disorder that affects the shape of your RBCs is called sickle cell anemia. The National Institutes of Health reports that sickle cell disease affects the quality of your blood and causes below-normal hemoglobin levels. As well as the usual symptoms of anemia, sickle cell disease can result in jaundice because of too much bilirubin is in the blood as well as pale colored stool.26

Other Causes of Low Hemoglobin Levels

Other, less common reasons for hemoglobin levels dropping below normal can include any of the following:

Endurance exercise. Researchers have found that endurance training can affect hemoglobin levels and hematocrit. Interestingly, mixed training or just power training doesn’t affect RBC indices.27

Gastric bypass surgery. The journal Hepato-Gastroenterology reported that gastric surgery can affect nutrient absorption. In time, the lack of iron in the body can cause low hemoglobin levels and possible signs of anemia.28

Liver disease. The Annals of Gastroenterology reported that advanced liver disease can cause anemia because liver dysfunction prevents iron absorption.29

Cancer. Various types of cancer can destroy red blood cells and cause dangerously low hemoglobin levels. Also, if cancer affects the internal organs like the pancreas, liver or kidneys, this can result in anemia due to low iron levels.

Low Hemoglobin Treatment (How to Increase Hemoglobin)

What is the best way to treat low hemoglobin and raise levels to be within the normal range? In most cases, successfully treating anemia means diagnosing the type of anemia and addressing the underlying issues.

Iron supplements for iron deficiency anemia

If you are diagnosed with iron-deficiency anemia, then your doctor may recommend a course of iron supplements to boost Hgb in your blood.

The journal Hematology Reports states that very often, iron supplementation is recommended during pregnancy if hemoglobin levels dip below normal. Doctors usually take blood tests to determine the amount of hemoglobin in red blood cells.30

Increase folate intake

To help address iron-deficiency anemia, doctors may also recommend taking folate along with iron supplements.

A study published in the International Journal of Obstetrics and Gynaecology found that folate supplements along with iron were more effective at bringing up hemoglobin levels than just iron alone.31

Low hemoglobin diet

It is also possible to raise hemoglobin levels to normal by including in your diet foods that are rich in vitamin B-12, folic acid, and iron.

The American Society of Hematology reports that vitamin B12 deficiency anemia is often a result of diet. However, absorption issues in the gastrointestinal tract can also cause pernicious anemia because vitamin B12 is poorly absorbed.32

To help increase hemoglobin levels, doctors recommend eating the following foods:

  • Green leafy vegetables because of their iron and folic acid content
  • Dried fruits and nuts to boost iron levels
  • Beef because it contains heme iron and vitamin B12 and is readily absorbed by the body
  • Citrus fruits because of their folic acid levels

Increasing iron absorption

A low hemoglobin diet should also focus on increasing iron absorption in the body.

For example, the journal Critical Reviews in Food Science and Nutrition found that vitamin C can boost iron absorption. Ascorbic acid (vitamin C) helps the body to absorb more iron from plant-based sources of iron and protein.33

High Hemoglobin Levels

Having high levels of hemoglobin in your blood is quite rare. High hemoglobin levels are defined as values of more than 17.5 g/dL in men and 15.3 g/dL in women.3

Having too much hemoglobin in your blood can increase the thickness of the blood and cause problems with your circulation. The American Journal of Clinical Nutrition says that higher than normal hemoglobin levels affect the amount of oxygen that reaches cells in the body. This can also lead to high blood pressure and various cardiovascular problems.34

High Hemoglobin Symptoms

How do you know if you have too much hemoglobin in your blood? Dr. Laura J. Martin on WebMD says that some of the common symptoms of elevated hemoglobin can include:35

High Hemoglobin Causes

The most common cause of having raised levels of hemoglobin that isn’t a result of a medical condition is living at high altitudes.

According to Dr. Charles Patrick Davis on eMedicineNet, other reasons for Hgb above the normal range include:36

  • Smoking
  • Various types of cancer
  • Polycythemia vera (a disorder of your bone marrow)
  • Lung disease
  • Extreme dehydration

High Hemoglobin Treatment

Treating the causes of higher than normal levels of hemoglobin can be a challenge. Dr. Siamak N. Nabili on eMedicineNet reports that medical intervention is usually necessary to lower hemoglobin levels. If you are prone to having elevated hemoglobin, it’s important to keep yourself well-hydrated.37

FAQ About Hemoglobin

What else should you know about hemoglobin and what questions do many people have regarding what to do when hemoglobin is low?

Can I test for low hemoglobin levels at home?

Yes. The U.S. Food and Drug Administration (FDA) has approved certain home testing kits for hemoglobin. For many people who are prone to low hemoglobin and hematocrit or elevated hemoglobin, hemoglobin testing kits can help to regularly monitor their blood work.2

Are there side effects when taking iron supplements to boost hemoglobin?

Yes. Taking iron supplements to boost your hemoglobin levels has some side effects such as constipation. Doctors from the Mayo Clinic say that some of the side effects of oral iron tablets can include:38

If you have any of the above side effects from iron supplements, you should speak with your doctor.

What are the signs and symptoms of taking too much iron?

Taking too many iron supplements can lead to iron poisoning. Dr. Louise Chang on WebMD warns that the signs of overdosing on iron supplements are the following:39

You should seek emergency care if you or a child has swallowed too many iron supplement pills.

What is hemoglobin A1c?

Dr. Gary L. Horowitz from Harvard Medical School says that hemoglobin A1c is the average blood glucose concentration in red blood cells. Testing levels of hemoglobin A1c can help diabetics manage their symptoms better and can help to monitor fasting glucose values.40

This ideal reference range of hemoglobin A1c (glycated hemoglobin) is between 4.8% and 5.9%. However, anything less than 7.0% should be acceptable for people with diabetes.

Related articles:

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