Understanding Haemoglobin Levels: How Low Is Too Low, Red Flags To Watch Out For

Haemoglobin is the iron-rich protein in red blood cells. It carries oxygen from the lungs to different parts of the body and returns carbon dioxide back to the lungs. Haemoglobin (Hb) is what gives blood its red colour and helps in respiration. About 70 percent of the body's iron is found in haemoglobin and in muscle cells called myoglobin. When the body lacks iron, it can impact haemoglobin levels. And when you have low haemoglobin, it affects your health severely.

Haemoglobin levels vary depending upon age and sex and is checked through Complete Blood Count (CBC). Speaking to NDTV, Dr Manisha Arora, Director - Internal Medicine at the CK Birla Hospital, Delhi shared how low is too low for haemoglobin. She also shared signs and symptoms of low haemoglobin, which should prompt individuals to check their levels.

Ideal haemoglobin level

Haemoglobin indicates the blood's capacity to carry oxygen, the vital fuel the body needs, said Dr Arora. "For most adult men, a healthy, normal level sits between 13 and 15 grams per deciliter (g/dL), and for adult women, it's a little lower, usually 12 to 14 g/dL. When levels drop below these ranges, it is called anaemia."

If haemoglobin is just slightly below normal, hovering around 10-12 g/dL, it's considered mild anaemia. With this condition, a person might feel a bit off but it's manageable. Things get more serious with moderate anemia, which is typically in the 8-10 g/dL range.

Dangerously low haemoglobin level

Dr Arora said, "The biggest concern is when haemoglobin falls below 8 g/dL; that's defined as severe anaemia and can truly be life-threatening, if it's not addressed quickly. If the haemoglobin level drops below 7 g/dL, it's a critical situation that almost always requires a blood transfusion and immediate medical attention to figure out exactly why it happened."

Symptoms of low haemoglobin level

When haemoglobin is low, the blood can't carry enough oxygen, and the whole body starts to feel it. This lack of oxygen is what causes that overwhelming fatigue and weakness, even when a person hasn't done much.

Common issues include looking pale, feeling dizzy, getting headaches, and experiencing shortness of breath or a fast, fluttering, irregular heartbeat.

Some people also find their hands and feet are constantly cold, their nails become brittle, and they might even have odd cravings for things that aren't food, like ice or dirt (called pica).

In the most severe cases, where oxygen starvation is significant, a person could experience chest pain, fainting spells, and trouble thinking clearly. These symptoms often show up over time and can be easy to ignore at first, but if there is persistent fatigue and a person just can't keep up physically, it's a definite sign that haemoglobin levels should be checked and necessary steps should be taken.

What happens when your haemoglobin falls below 8 g/dL?

Firstly, the body experiences significant oxygen deprivation, leading to severe anaemia that impacts organ function and daily activities. Common symptoms include extreme fatigue, profound weakness, shortness of breath even at rest, dizziness, lightheadedness, and pale skin due to reduced red blood cell delivery of oxygen to tissues. To compensate for this, the heart starts beating faster or irregularly, potentially causing palpitations, chest pain, or cardiac strain, which increases the risks of complications like heart failure in vulnerable individuals.

When you have low haemoglobin levels, it usually signals underlying issues such as nutritional deficiencies (iron, B12, folate), chronic blood loss from ulcers or heavy menstruation, kidney disease, cancer, infections like malaria, or bone marrow disorders.

Below 8 g/dL is considered to be dangerously low; especially for women (normal >12 g/dL) and men (>13 g/dL). This should prompt urgent medical evaluation to prevent life-threatening outcomes like organ damage as mortality rates increase significantly when haemoglobin levels fall under 6-7 g/dL.

Disclaimer: This content including advice provides generic information only. It is in no way a substitute for a qualified medical opinion. Always consult a specialist or your own doctor for more information. NDTV does not claim responsibility for this information.