9 Signs of Vitamin B12 Deficiency (Don’t Ignore #3)

Last Updated on September 22, 2025 by Sunit. S. Ekka

The signs of vitamin B12 deficiency include fatigue, muscle weakness, irritability, and a rapid heart rate. It is a very important vitamin for maintaining the optimum health of our body.

In this article, we will discuss all the signs of vitamin B12 deficiency in detail. We will also learn how it can impact your health, who are at more risk and food sources of vitamin B12.

Why vitamin B12 is essential for our body

Vitamin B12 plays a vital role in various physiological processes in our body, like the production of red blood cells. A water-soluble vitamin, also called as cobalamin, is naturally present in dairy products. We will go into detail about its food sources. Let’s find out what its role is in our body.

1: Formation of RBC

So the most important role is the formation of Red Blood Cells (erythrocytes). The process of formation of RBC is termed erythropoiesis. In simple terms, vitamin B12 helps in the formation of blood in our body.

These new erythrocytes replace the oldest erythrocytes (normally about one per cent) that are phagocytosed and destroyed each day. Folate, vitamin B12, and iron have crucial roles in erythropoiesis.

The deficiency of folate or vitamin B12 impairs DNA synthesis and causes erythroblast apoptosis, resulting in anaemia from ineffective erythropoiesis¹.

2: Important for brain health

Vitamin B12 is also very important for the health of our nervous system, which includes our brain, neurons, and all the nerves we have.  It helps in the synthesis of myelin. The myelin sheath surrounds the axons of many nerves and serves as electrical insulation, thereby facilitating fast conduction velocity².

Its deficiency can cause neuropathy, cognitive decline, and psychiatric issues, particularly in older adults³.

3: Formation of DNA

Its third most important role is in the formation of DNA; it is also very important for the formation of DNA in our body. Vitamin B12 is especially involved in the DNA synthesis of myelin‐producing oligodendrocytes and the synthesis of myelin².

4: Healthy skin and hair

And fourth, it has a huge role in the health of our skin and the health of our hair. 

What Causes Vitamin B12 Deficiency?

So what can happen in our body due to its lack? Since it has a major role in the formation of RBC in our body, its deficiency can cause Pernicious Anemia. It’s a blood condition due to which we feel tired and weak all over the body.

So the most important reason for pernicious anaemia is the inability to absorb the dietary vitamin B12. Whatever dietary vitamin B12 we take through food, our body is not able to properly absorb it.

We may be taking sufficient dietary vitamin B12, and we may be eating food sources rich in vitamin B12, but our bodies are not able to absorb it. And it goes out, due to which there is low vitamin B12 in our body, which causes pernicious anaemia. 

Also read: What are the signs of low blood pressure?

9 Common Signs & Symptoms of Vitamin B12 Deficiency

So, here’s the list of early signs of vitamin B12 deficiency. If you find these signs, you must consult your doctor and take appropriate steps as soon as possible.

1. Muscle weakness: So first of all, we will have muscle weakness. Even if we do some work, we will get tired immediately after walking a little distance. We will feel tired, and pain may also develop in the muscles.
2. Nausea: The second symptom is nausea, meaning we will feel like vomiting. There will always be a tendency to vomit; if you brush or take anything in your mouth, then you will feel like vomiting.
3. Decreased appetite: After that, the third symptom is decreased appetite, that is, you will feel less hungry. You will not feel like eating, will feel that your stomach is full, and will not feel like eating.
4. Irritability: The next is irritability, that is, you will be irritable throughout the day. You get irritated, angry, and irritable; normally when you should be in a good mood, you will always have an irritable mood.
5. Lack of energy: After that, we feel a lack of energy. There will be no strength in your body, you will feel sluggish or lethargic throughout the day, and you will feel that you go to sleep, do not work, and remain lying somewhere.
6. Increased heart rate: The next symptom is increased heart rate. You feel that your heartbeats are increased. These are all the symptoms of its deficiency, in a way is a sign of pernicious anaemia.

So as soon as you see these symptoms, you should immediately visit the doctor and talk to them about what could be the reason. And if there is a deficiency of Vitamin B12, it will be completely confirmed by the report of the blood test. 

Who is at Risk of Vitamin B12 Deficiency?

So what are its risk factors, ie who is more likely to have vitamin B12 deficiency?

1. Family history: So the first point is family history, that is, if someone in your family has a problem with vitamin B12 deficiency, then it may happen in the child too.
2. Type-1 Diabetes: After that, type-1 diabetes, those who have a sugar problem, have type-1 sugar problems, and those who have diabetes problems also have a higher risk of vitamin B12 deficiency.
3. Strict vegan: The next risk factor is strictly vegetarian food, that is, if you are strictly vegetarian. Even if you don’t take milk and do not even eat eggs, you are more likely to have it because vitamin B12 mostly comes from animal sources. It is not found in vegetarian sources, so those who are strictly vegetarian are more likely to have it.
4. Gastrointestinal surgery: For those who have gastrointestinal surgery, if some part of the stomach has been removed, there is a possibility of having this problem. Even in intestinal operation, even if you take sufficient dietary vitamin B12, if the body is not able to take it, it is excreted. So this can be a reason.
5. HIV: Next, people who have HIV can also get a vitamin B12 deficiency.
6. Old age: It is found more in the elderly; elderly people have decreased capacity to absorb vitamin B12. Even if they consume rich dietary sources, they suffer from vitamin B12 deficiency.

Best Food Sources of Vitamin B12

So this was it, what are its risk factors? Now, the most important point is from which food sources do we get vitamin B12?

1. Milk & Yoghurt: As I mentioned earlier, it is found more than in animal sources, so what can a strict vegetarian take? If you are strictly vegetarian, then you do not need to worry; if you drink milk and eat curd, then it also contains sufficient vitamin B12. With that, if you can compromise with eggs, then you can eat eggs too.
2. Meat: After that, meat, i.e. chicken, or mutton, all of these also contain vitamin B12 in plenty.
3. Egg: And after that again eggs, as I said that eggs are also a rich source of vitamin B12.
4. Fish: After that, those who eat fish, fish, fish are also rich in vitamin B12.
5. Fortified cereals: Then the fortified cereals, about which you know, also contain Vitamin B12 in sufficient quantity.

So if you keep consuming all these foods regularly, then you will not be deficient in Vitamin B12, and yet if you are deficient in Vitamin B12, then you should contact your doctor to discuss what dietary supplements you have to take. will benefit to a great extent.

Conclusion: Treatment and Prevention

So I hope you find this article on the signs of vitamin B12 deficiency very helpful. I keep on bringing similar articles. If you liked this article, then do not forget to like and share it because it is becoming a very widespread problem. Nowadays, you will observe that youngster gets irritated very quickly, mood swings very quickly, then this is also one of the reasons. It can be that there is a deficiency of vitamin B12 because vitamin B12 is very important for maintaining brain cells.

Have you experienced any of these signs of Vitamin B12 deficiency? What helped you? Share your story in the comments below!

Keep reading: What Vitamin C Good For? 8 Deficiency Symptoms Not To Ignore

FAQ on Vitamin B12 Deficiency

Sunit. S. Ekka

The author is a physiotherapist who has been practising for the last 17 years. He holds a Bachelor's in Physiotherapy (BPT) from SVNIRTAR (Swami Vivekananda National Institute of Rehabilitation and Research), one of the prestigious physiotherapy schools in India.

Whatever he learns dealing with his patient, he shares it with the world through blogs and e-books. He also owns a YouTube channel, "Sunit Physiotherapist" with over 8 lakh active subscribers. Here, he shares everything he gets to learn serving the patient.