by admin-blog-kh | February 20, 2026 7:30 am
Vitamin B12, or cobalamin, is an essential water-soluble vitamin that supports healthy red blood cells, nerve cells, DNA, and RNA. Since the body cannot produce it, we must obtain B12 from food or supplements. It is stored in small amounts in the liver, with excess excreted through urine. Rich sources include animal products such as milk, eggs, fish, and meat, as well as plant-based options such as nutritional yeast, algae, and shiitake mushrooms. For absorption, B12 must bind to a protein called intrinsic factor in the stomach. A deficiency can lead to vitamin B12 deficiency anaemia, where red blood cell production falls or abnormal cells form, reducing oxygen delivery throughout the body. This often results from a lack of intrinsic factor due to autoimmune conditions, stomach surgery, or chronic gastritis. Adults need about 2.4 mcg every day, with higher requirements during pregnancy and breastfeeding.
Subtle deficiency signs include fatigue, tingling sensations, mood swings, memory problems, glossitis, and headaches. Left untreated, it may progress to serious neurological issues. If symptoms appear, consult your doctor for diagnosis and treatment, which may include supplements or dietary adjustments.
Vitamin B12 is an organic compound that the body uses to make and sustain healthy nerve cells, red blood cells, DNA, and RNA. It is also called cobalamin. Your body cannot make its own vitamin B12, so you must obtain it through your diet. Vitamin B12 is a water-soluble vitamin. The body can store a few years’ worth of vitamin B12 in the liver, amounting to about 3–4 mg. Any excess vitamin B12 beyond storage capacity is eliminated by the kidneys through urine.
Vitamin B12 primarily comes from animal sources. Milk, yoghurt, cheese, eggs, fish, and meat are good sources. Plant-based sources of vitamin B12 are fewer, but they do exist – shiitake mushrooms, nutritional yeast, and algae are examples.
For vitamin B12 to be absorbed from food, your stomach must be sufficiently acidic to break down food and release the vitamin. Once released, B12 combines with a protein called intrinsic factor, which enables its absorption through the intestinal wall.
Vitamin B12 deficiency anaemia is a condition in which the body has very low concentrations of red blood cells due to a vitamin B12 deficiency[6]. Vitamin B12 plays a critical role in the production of healthy red blood cells. Without it, the red blood cell counts drops, reducing oxygen supply to various parts of the body. This is a serious condition.
Sometimes, the red blood cells produced without adequate vitamin B12 are abnormally large and oval-shaped, instead of round as they should be. This is referred to as megaloblastic anaemia. In some cases, red blood cells also die faster than normal.
One of the main causes of vitamin B12 deficiency anaemia is a lack of intrinsic factor, the protein that helps vitamin B12 get absorbed through the lining of the small intestine. The body may be unable to produce intrinsic factor because of chronic gastritis, removal of a portion of the stomach, or autoimmune conditions.
The vitamin B12 requirement depends on age. Children under 3 need only 1 mcg per day. The average adult requires 2.4 mcg per day. During pregnancy, the requirement is about 2.6 mcg per day. While breastfeeding, a person may need about 2.8 mcg per day.
According to dieticians, here is the approximate amount of food an average adult would need to eat to get their daily dose of vitamin B12:
For vegetarians who avoid meat and fish, vitamin B12 sources are limited. Regular consumption of milk, curd, and eggs (if ovo-vegetarian) helps. Some fortified breakfast cereals and nutritional yeast (available in cities) may also provide small amounts.
This assumes that the food listed is your only source of vitamin B12 for that day.
Vitamin B12 deficiencies usually develop gradually. They may occur because you are not consuming enough B12-rich foods, or because your body is not absorbing it efficiently. You do not have to wait until your deficiency becomes severe before taking action. By noticing the subtle signs early, you can minimise its impact:
If you notice any of these signs, especially if multiple symptoms occur frequently, consult your family doctor[8]. A vitamin B12 deficiency can significantly affect your quality of life, but timely treatment can prevent complications.
Your doctor will likely conduct a simple blood test to check your blood count and vitamin levels. Based on your results and symptoms, they may prescribe the appropriate treatment. Additional tests may be recommended depending on severity and possible causes. Always consult a doctor before taking supplements. Most patients only need supplements for a short period, after which dietary sources are usually sufficient.
If you’re experiencing persistent fatigue, tingling, or memory changes, early testing can help prevent long-term complications. Kauvery Hospital, with branches in Chennai, Hosur, Salem, Tirunelveli, and Trichy, offers accurate diagnostic testing and expert medical care to identify vitamin B12 deficiency and guide safe, effective treatment[9].
What are the subtle early signs of vitamin B12 deficiency?
Early signs include fatigue, tingling or numbness in hands and feet, mood changes, memory problems, muscle weakness, headaches, and a red, inflamed tongue. Symptoms usually develop gradually.
Why does vitamin B12 deficiency cause constant tiredness?
Vitamin B12 is required to produce healthy red blood cells. Without enough B12, oxygen delivery to tissues decreases, leading to weakness, low energy, and persistent fatigue.
Can vitamin B12 deficiency cause neurological symptoms?
Yes. Low vitamin B12 can damage nerve cells and the protective myelin sheath, causing tingling sensations, numbness, balance issues, memory loss, and slowed thinking.
What causes vitamin B12 deficiency besides poor diet?
Deficiency may result from poor absorption due to low intrinsic factors, chronic gastritis, autoimmune conditions, stomach surgery, or certain medications that reduce stomach acid.
Who is at higher risk of vitamin B12 deficiency?
Vegetarians, older adults, pregnant women, people with digestive disorders, and those who have undergone stomach surgery are at higher risk of developing deficiency.
How much vitamin B12 does an adult need daily?
Most adults require about 2.4 micrograms per day. Pregnant women need about 2.6 micrograms, and breastfeeding women require around 2.8 micrograms daily.
How is vitamin B12 deficiency diagnosed?
Doctors diagnose it through a blood test that measures vitamin B12 levels and checks for anaemia. Additional tests may be done if nerve symptoms are present.
Can vitamin B12 deficiency be reversed?
Yes. With timely treatment through supplements, injections, or dietary changes, most symptoms improve. However, long-standing nerve damage may not be fully reversible.
Is vitamin B12 deficiency serious if left untreated?
Yes. Untreated deficiency can lead to severe anaemia, permanent nerve damage, cognitive decline, and increased risk of neurological complications.
When should I see a doctor for possible B12 deficiency?
Consult a doctor if you experience persistent fatigue, tingling sensations, memory changes, mood disturbances, or multiple symptoms that do not improve.
Kauvery Hospital is globally known for its multidisciplinary services at all its Centers of Excellence, and for its comprehensive, Avant-Grade technology, especially in diagnostics and remedial care in heart diseases, transplantation, vascular and neurosciences medicine. Located in the heart of Trichy (Tennur, Royal Road and Alexandria Road (Cantonment), Chennai (Alwarpet, Radial Road & Vadapalani), Hosur, Salem, Tirunelveli and Bengaluru, the hospital also renders adult and paediatric trauma care.
Chennai Alwarpet – 044 4000 6000 • Chennai Radial Road – 044 6111 6111 • Chennai Vadapalani – 044 4000 6000 • Trichy – Cantonment – 0431 4077777 • Trichy – Heartcity – 0431 4077777 • Trichy – Tennur – 0431 4022555 • Maa Kauvery Trichy – 0431 4077777 • Kauvery Cancer Institute, Trichy – 0431 4077777 • Hosur – 04344 272727 • Salem – 0427 2677777 • Tirunelveli – 0462 4006000 • Bengaluru – 080 6801 68011
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