causes of low hemoglobin

Low Hemoglobin – Why Do I Have It? Dr Vivek Baliga, Baliga Diagnostics, Explains

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Low hemoglobin levels are very common. However, they remain a concern for many who see it on their report. But why do some people have low hemoglobin levels? How low can hemoglobin go before it needs treatment?

Let’s take a look. But first….

What Is Hemoglobin?

We all have heard the term hemoglobin, but do we know what it is?

In the simplest of terms, hemoglobin is a protein that transports oxygen to the tissues. It picks up this oxygen in the lungs and delivers it to the organs. Once oxygen has been delivered, it carries the carbon di-oxide generated back to the lungs.

In the word hemoglobin, ‘heme’ means iron and ‘globin’ is a protein. The basic structure of hemoglobin is 4 protein molecules that are attached to iron.

Hemoglobin is sometimes abbreviated ‘Hb’.

If you have a normal hemoglobin level, then the oxygen delivered to your tissues and organs will be normal. If your hemoglobin is low, then the oxygen reaching the tissues reduces.

This can make the individual very breathless and tired.

What Is The Normal Hemoglobin Value?

The value of hemoglobin differs between men and women and also depends on the age.

The normal hemoglobin in adult men is around 13 to 18 gm/dL. In adult women, the values range between 12 to 15 gm/dL.

What Causes Low Hemoglobin?

There are a number of reasons why you can have low hemoglobin. Some of them can be treated very easily, while some require extensive investigations.

I am not going to go into too much details about why hemoglobin levels can decrease. I will however mention the common reasons and the investigations that are needed to find out the cause.


1. Low iron levels

2. Low levels of vitamin B12

3. Blood loss from the gut

4. Medications such as cancer treatment drugs

5. Problems with the bone marrow

6. Kidney failure

7. Rare diseases such as sickle cell anemia, leukemia and thalassemia

8. Hypothyroidism

Let’s take a look at some of these in brief.

1. Low Iron Levels

This is probably one of the most common reasons why hemoglobin levels can be low. Low iron levels leading to low hemoglobin levels fall under the class of ‘nutritional anemia’.

Hemoglobin levels that are low because of low iron levels in the blood is called ‘iron deficiency anemia’ or IDA.

Iron deficiency anemia is particularly common in vegetarians. This is because their diet is low in iron.

why do I have low hemoglobin

Sometimes, iron levels can be low because iron that is consumed in the diet is not getting absorbed in the gut.

If you are low in iron, then your blood test report will reveal a finding called ‘microcytic hypochromic anemia’. The word ‘microcytic’ means ‘small cell’ while the word ‘hypochromic’ means ‘pale colour’.

In other words, in iron deficiency anemia, the blood cells will be small and pale.

So how can iron deficiency anemia be corrected?

Firstly, laboratory studies will need to be conducted to confirm the low levels of iron. A simple blood test will reveal this.

Once confirmed, you doctor will start you on oral iron supplements. These are usually taken after food with water. By the way, these supplements can make the stools black, so don’t panic if they do.

Sometimes however, oral iron supplements prescribed may not work. This is because the iron is not absorbed by the gut. In such situations, intravenous iron supplements may need to be prescribed.

Once the iron levels are corrected, the hemoglobin levels tends to correct itself. It can take some time though (sometimes up to a few weeks to months).

Therefore, if hemoglobin levels are very low, then your doctor may not just advise investigations; they may also want you to have a blood transfusion.

2. Low Vitamin B12 levels

Once again, this is a type of nutritional anemia. It is usually seen in vegetarians.

Vitamin B12 has a number of different functions. One of them is to maintain healthy red blood cell production from the bone marrow.

If vitamin B12 levels are low, then the red blood cells that are produced will be immature and large. They do not carry much hemoglobin.

In other words, the anemia will be a macrocytic anemia.

how do I know if my hemoglobin is low

As mentioned previously, one reason why you might be vitamin B12 deficient is because you follow a vegetarian diet. Regular consumption of vegetables without intake of non-vegetarian protein can lead to low levels of vitamin B12.

Another reason why vitamin B12 levels might low is the deficiency of something called ‘intrinsic factor’.

Intrinsic factor is a compound that is released in the stomach and that binds to vitamin B12. This binding aids in absorption of this vitamin.

If low vitamin B12 levels are the reason for your low hemoglobin, then there is no need to worry. Simple supplementation in the form of tablets or injections is sufficient. Fortified cereals also now contain vitamin B12.

3. Blood Loss

Bleeding from the digestive tract can lead to low hemoglobin levels.

Bleeding of any sort is obviously concerning. Blood loss from the gut can be due to multiple reasons, and all patients who are losing blood require investigating.

If blood is oozing out from the stomach, then the stools passed will be tarry and black due to the presence of digested blood.

Bleeding from the stomach is usually due to bad gastritis. This can be due to ingestion of pain killer medication or blood thinners such as aspirin. These tablets can irritate the stomach lining and increase acid production.

A diagnosis of bleeding from the stomach is made by an upper gastro-intestinal endoscopy, sometimes called an upper GI endoscopy.

Similarly, if blood is oozing out within the colon, it is usually bright red in color. This is because this blood is not digested.

Blood from the colon can be due to piles or from a small tumor or inflammation. A coloscopy test is needed to investigate this.

If low hemoglobin is due to blood loss, then replacing the blood by means of a transfusion may be needed. The cause will also have to be identified and treated as well.

4. Problems With The Bone Marrow

The bone marrow is responsible for the formation of blood within the body.

If it does not function normally, you could end up with a low hemoglobin.

Not always is it easy to pick up a bone marrow problem from a simple blood test. However, if you have a low hemoglobin and all your other blood tests are normal (such as iron levels, vitamin B12 etc), then your doctor may consider this as a possibility.

If your doctor suspects that your bone marrow is not functioning normally, they will likely refer you to a hematologist.

You may undergo tests such as bone marrow examinations to determine whether the bone marrow is working normally. If problems are detected, you may require additional investigations and certain special treatments.

5. Kidney Disease

Low hemoglobin from kidney disease occurs because of the lack of a hormone called erythropoeitin.

kidney disease and low hemoglobinThis hormone is secreted by a normal functioning kidney. The hormone acts on the bone marrow and stimulates the formation of new blood cells.

The word erythropoeitin is derived from the words ‘erythro’ meaning ‘red’ and ‘poeisis’ meaning ‘synthesis’.

If you suffer from kidney disease and low hemoglobin, your doctor may recommend erythropoeitin injections as a form of treatment.

6. Other causes

There are many other reasons why your hemoglobin may be low. However, a detailed description is out of the scope of this article.

How Will I Know If My Hemoglobin Is Low?

If you suffer from anemia, you may find yourself being more tired than usual.

Those who have very low levels may begin to notice breathlessness when they exert themselves. They may even feel this when doing regular household activities.

Some people with low levels of hemoglobin may experience chest pain. This is because the heart does not get the oxygen and nutrients it needs to sustain itself.

Finally, some people may experience weight loss, particularly if there is a tumor or cancer causing anemia.

What Do I Do If I Have Low Hemoglobin?

If you have low hemoglobin, talk to your doctor about it.

Your doctor may want to put you through certain investigations. Once these tests have been done, you should have a better idea as to why you have anemia and what treatment can help you.

How Do I Keep My Hemoglobin Normal?

There are many ways you can keep your hemoglobin levels within the normal range.

  1. Eat a healthy, balanced diet
  2. Perform plenty of exercise
  3. Avoid smoking
  4. Avoid excessive alcohol
  5. Avoid popping in painkillers every time you have a little pain
  6. Visit your doctor
  7. Get your blood tested at least once a year.

Closing Remarks

A low hemoglobin level is a common problem, and could be due to a number of reasons. Make sure you get your blood tested at least once a year. Simple measures can help keep your hemoglobin levels under control.

Dr Vivek Baliga B
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2 thoughts on “Low Hemoglobin – Why Do I Have It? Dr Vivek Baliga, Baliga Diagnostics, Explains”

    1. Heart Sense Team

      Thank you for your comment Sir. It is very interesting that you bring this up, as a paper published in 2013 has shown that yoga could help increase hemoglobin levels. While they do not mention pranayama as such, they state that asanas of Trikona and its variations, Sarvanga, Surya namaskara and Yoga mudra can all increase hemoglobin. However, better results were seen with those who also had an iron supplement. You can read this paper here –

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