Low Red Blood Cells: Causes, Symptoms & Treatment

Zu wenig rote Blutkörperchen: Ursachen, Symptome & Behandlung

In our body, approximately 5-6 liters of blood circulate, which consists of various components. The largest part of it, about 99%, is made up of red blood cells, also known as erythrocytes. Among other things, they are responsible for the red color.

Normally, an adult has several million red blood cells in the blood. As soon as they break down, the body produces the same number of red blood cells again. However, various reasons can disrupt this process, leading to what is known as anemia(1). In this article, you'll find out what can cause this and what you can do about it.

Key Points

  • Red blood cells are responsible for oxygen supply in your body. Therefore, if there are too few red blood cells, you will primarily feel tired and less efficient.
  • A deficiency in red blood cells is not a disease in itself but is a symptom of other diseases or deficiencies. Thus, the root cause must always be treated.
  • In most cases, a lack of red blood cells is caused by iron deficiency. This can be easily rectified with nutrient intake or supplementation.

Definition: What are red blood cells?

Red blood cells, also known as erythrocytes, make up the majority of human blood. Due to their unique shape, they are extremely flexible, allowing them to fit through even the smallest blood vessels.

On the one hand, they have the essential task of transporting oxygen from the lungs to all organs of the body. On the other hand, they are also responsible for the removal of carbon dioxide from the organs to the lungs, where it can be exhaled.

With anemia, you have too little hemoglobin in your blood.

Both substances are bound using hemoglobin. This protein is largely made of iron and gives our blood its red color. Therefore, it's also referred to as the red blood pigment. Hemoglobin is the most critical component of erythrocytes because, without it, they can't perform their function. Erythrocytes are measured with the hematocrit value. This value indicates the proportion of red blood cells in the blood.

Erythrocytes are produced in the bone marrow. A healthy person always has the exact same number of erythrocytes, ranging between 4.6 and 5.2 billion per milliliter. Their average lifespan is about 4 months, after which they are broken down in the spleen and excreted.

To ensure that the body always has the same number of red blood cells, a hormone called erythropoietin (EPO) is sent to the bone marrow, stimulating the production of new red blood cells (2).

Background: What you should know about a lack of red blood cells

In this section, we have compiled frequently asked questions about the topic of a lack of red blood cells.

What causes a lack of red blood cells?

You should know that a reduced number of red blood cells is usually not a disease in itself but can be a sign of a disease or a nutrient deficiency. Therefore, there are many different possible causes of anemia:

  • Genetic: Certain genetic defects affect, for example, the bone marrow or the kidney. They don't work optimally together, so the erythrocytes are too small, not produced in sufficient quantity, or are broken down too quickly.
  • Nutrient deficiency: Excessive alcohol consumption or a one-sided diet, in which you consume too little iron, folic acid, or vitamin B12, can prevent blood formation and thus lead to anemia. These three substances are prerequisites for the formation of hemoglobin. Especially iron deficiency is the most common cause of anemia (3).
  • Blood loss: If you lose a lot of blood, e.g., through a large wound or internal bleeding, like with a bleeding stomach ulcer, your body cannot produce new blood cells quickly. This can also occur with long and heavy menstrual bleeding.
  • Diseases: Cancer diseases such as leukemia (too many white blood cells, which prevent the formation of red blood cells), autoimmune diseases, viral infections, chronic organ disorders of the spleen, liver, intestine, or kidney, or even diabetes (kidney function impaired, so less EPO can be released) can trigger anemia(4).
  • Therapies: Not only the diseases themselves but also their treatments can cause anemias. Certain medications or chemotherapy can impair the functions of organs involved in blood formation.

Here, we only provide a rough overview of the various causes. The actual cause responsible depends on other factors. Only a doctor can definitively determine the cause through various tests.

Is it dangerous to have too few red blood cells?

Whether anemia is dangerous cannot be said categorically. It depends entirely on the root cause for the low number of red blood cells, which can range from a relatively harmless nutrient deficiency to a severe chronic illness. However, the most common cause of anemia is nutrient deficiency, especially iron deficiency.

If the affected individual already suffers from a chronic illness, anemia can exacerbate the original disease, increase mortality, or slow down the healing process (5). Anemia can also increase the risk of subsequent illnesses, such as dementia (6).

What are the symptoms of having too few red blood cells?

If there are too few red blood cells in your blood, there is also not enough hemoglobin present. This means that your body cannot be sufficiently supplied with oxygen. Primarily, this can cause the following symptoms(7):

  • decreased performance capability
  • fatigue
  • pallor
  • headaches
  • shortness of breath
  • breathlessness even with minor exertion
  • rapid heart rate
  • restless legs

These symptoms are not solely attributable to anemia, which is why anemia is often detected sooner rather than later.

Woman with headaches

With too few red blood cells, your body is supplied with too little oxygen. This often leads to headaches and decreased performance capability. (Image Source: Andre Piacquadio / Pexels)

If you notice these symptoms over a more extended period, you should consult a doctor.

In which patients is a lack of red blood cells common?

For some patients, anemia is more likely due to their physical condition:

  • Elderly: Anemia is by no means normal in older people. Often, the hormonal balance and eating habits simply change with age. It is also possible that organs may no longer absorb and process certain nutrients as effectively due to age. This can also be due to chronic diseases (8).
  • Pregnant Women: A so-called pregnancy anemia often occurs in the second half of pregnancy. During this development phase, the growing child needs a lot of iron, which it can only get from the mother. Additionally, the amount of blood increases overall, but the number of erythrocytes does not increase in the same proportion (9). This lowers the hematocrit value.
  • Premature Babies: The bone marrow of premature babies is not yet fully developed, and therefore cannot produce a sufficient number of erythrocytes (10).

Lack of red blood cells: What can you do about it?

Now you know that there can be many different causes for a lack of red blood cells. Depending on the original cause, there are different treatment options. We will introduce you to the basic therapy options. You should always discuss which specific options are suitable for you with your doctor.

Nutrient Intake

In case of a slight lack of red blood cells, a change in diet might already help. You should especially make sure to consume enough iron, Vitamin B12, and folic acid. These are essential for the formation of new red blood cells (11). We have compiled examples of foods that are particularly rich in these components for you.

Iron Vitamin B12 Folic Acid
Red meat (deer, roe deer, lamb, duck) Meat Tomatoes
soaked legumes Fish green vegetables
green vegetables Milk Oranges
Nuts, seeds, seeds Cheese Legumes, Nuts
Whole grain products Eggs Whole grain products

If you are currently on a diet or follow a strictly vegetarian or vegan diet, you should pay particular attention to your vitamin B12 levels.

Nuts and legumes

To remedy iron deficiency, a change in diet can help. Nuts and legumes contain a lot of iron, are healthy and tasty. (Source: Usman Yousaf / Unsplash)

In some cases, it might also be useful to supplement nutrient deficiencies with dietary supplements, such as iron supplements,.


Depending on the underlying condition, various medications can help with anemia. Tablets for oral intake, which can restore the iron balance, are usually suitable only for malnutrition, meaning when the body can also absorb the nutrients.

Vitamin C promotes the absorption of iron.

If organs such as the kidney or intestine are damaged by a chronic inflammatory disease and the body cannot absorb the iron, injection solutions are more appropriate. These go directly into the blood and don't need to be processed by the body first.

Blood Transfusion

In particularly severe cases or advanced anemia, a blood transfusion can help remedy the lack of red blood cells. This involves transferring missing red blood cells. However, this can also lead to an excess of iron (12). It is essential in this case to primarily address the underlying condition.


A lack of red blood cells is often a symptom of another disease or nutrient deficiency. You should get examined by a doctor to obtain accurate values, especially if you suffer from diseases like cancer, diabetes, or organ impairments.

After discussing further steps with them, you should continue to have your blood values checked regularly. In most cases, anemia can be remedied with a balanced diet or by supplementing nutrients. In any case, you should regularly have your values checked by a doctor, so that timely assistance can be provided if needed.


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  7. Miller JL. Iron deficiency anemia: a common and curable disease. Cold Spring Harb Perspect Med. 2013;3(7):a011866. Published 2013 Jul 1. doi:10.1101/cshperspect.a011866 Source
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  11. Briguglio M, Hrelia S, Malaguti M, Lombardi G, Riso P, Porrini M, Perazzo P, Banfi G. The Central Role of Iron in Human Nutrition: From Folk to Contemporary Medicine. Nutrients. 2020 Jun 12;12(6):1761. doi: 10.3390/nu12061761. PMID: 32545511; PMCID: PMC7353323. Source
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