What is Vitamin B12 Deficiency and What Are Its Symptoms?

Vitamin B12 deficiency occurs when the body cannot get or absorb enough cobalamin—a crucial vitamin needed to produce healthy red blood cells, protect the nervous system, and synthesize DNA. This deficiency can lead to a wide range of health issues, from lingering fatigue to memory loss. Dietary habits and gastric surgeries, in particular, directly affect the levels of this vital nutrient.

• Vitamin B12 is not produced in the human body; it must be obtained externally through animal-based foods or supplements.
• Because the liver's B12 stores can meet the body's needs for 400 to 500 days, deficiency symptoms may appear quite late.
• People who have undergone stomach reduction (bariatric) surgery are among the highest risk groups due to impaired absorption.
• Untreated deficiencies can pave the way for permanent nerve damage and severe anemia.
• Treating the deficiency does not cause weight gain; on the contrary, it normalizes appetite and boosts energy by speeding up carbohydrate metabolism.

What is Vitamin B12 Deficiency?

Vitamin B12 (cobalamin) is a water-soluble, heat-sensitive essential vitamin that plays a key role in cell metabolism. Our bodies cannot produce this vitamin on their own. To maintain a healthy life, we must consume Vitamin B12 through our diet, pass it smoothly through the stomach and intestinal tract, and absorb it into the bloodstream. Any excess vitamin that enters the blood is stored in the liver. This backup reserve in the liver can meet the body's needs for more than a year, even if dietary intake is insufficient.

When these stores are depleted, the cell division process slows down, and the protective sheaths (myelin) surrounding nerve cells begin to suffer damage. The prevalence of this common problem ranges from 5 to 40 percent, depending on dietary habits and age. This rate climbs significantly higher, especially in individuals aged 50 and over, as stomach acid decreases with age.

Causes and Risk Factors of Vitamin B12 Deficiency

Two main factors usually lie at the root of B12 deficiency: inadequate nutrition and absorption disorders in the digestive system. Vegans or strict vegetarians who do not consume animal products are directly at risk because they cannot get enough B12. However, diet is not the only cause of deficiency.

Absorption Issues and Stomach Disorders

Stomach acid separates Vitamin B12 from the proteins in food, making it ready for absorption. Gastrointestinal disorders that damage the intestinal lining, such as Celiac or Crohn's disease, prevent the vitamin from passing into the blood. Additionally, a Helicobacter pylori infection can lead to gastritis in the stomach, severely reducing absorption. Autoimmune gastritis and pernicious anemia also halt the production of a protein called "intrinsic factor," which the body needs to absorb B12, thereby laying the groundwork for deficiency.

B12 Deficiency After Stomach Reduction Surgery

Individuals who have undergone stomach reduction (sleeve gastrectomy or gastric bypass) as part of obesity surgery are the most critical risk group for Vitamin B12 deficiency. Because a large portion of the stomach is removed or bypassed during these operations, the production of stomach acid and intrinsic factor drops dramatically. The vitamin ingested with food cannot be adequately processed in the stomach and therefore cannot be absorbed by the small intestine. For this reason, it is mandatory for bariatric surgery patients to have regular lifelong blood tests and use supplements under a doctor's supervision.

Medication Use and Lifestyle

Long-term use of stomach-protecting drugs (proton pump inhibitors) and medications containing metformin used in diabetes treatment can suppress B12 absorption. Furthermore, while excessive alcohol consumption depletes liver stores, excessive coffee consumption and improper diet programs can also disrupt the overall vitamin balance. The increase in complaints about vitamin deficiency after summer and during seasonal transitions is closely related to changing dietary routines.

What Are the Symptoms of B12 Deficiency?

Symptoms of Vitamin B12 deficiency may not become apparent until the condition reaches a serious stage. Symptoms usually start mild and intensify as the body's stores are completely emptied. Based on the affected systems, we can list the complaints as follows:

• Physical Symptoms: Constant fatigue, low energy, feeling cold, pale or slightly yellowish skin, shortness of breath even with mild exertion, and heart palpitations.
• Neurological and Psychological Symptoms: A pins-and-needles sensation (tingling) and numbness in the hands, arms, and legs, forgetfulness, difficulty focusing, mood changes such as depression, irritability, and anxiety.
• Digestive System Symptoms: Frequently recurring mouth ulcers (canker sores), redness and swelling of the tongue, loss of appetite, weight loss, diarrhea, or constipation.
• Other Symptoms: Hair loss, muscle weakness, vision problems, and developmental delays in babies.

What Foods Contain Vitamin B12?

The most effective way to meet the body's need for this vitamin naturally is to regularly consume animal-based foods. Protein-rich foods like red meat, chicken, and turkey are the strongest sources. Among seafood, tuna, salmon, trout, shrimp, and sardines contain high levels of B12.

For those who enjoy offal, liver and kidneys are absolute powerhouses of B12. For vegetarians who do not eat meat but do consume animal products, eggs, yogurt, kefir, milk, and various cheeses are ideal options to meet daily needs. Since plant-based foods do not naturally contain B12, it is absolutely essential for vegans to take supplements.

How Is B12 Deficiency Diagnosed at the Hospital?

Diagnosing a B12 deficiency at the hospital is possible with a very quick and simple blood test. After listening to your complaints and conducting a physical examination, your doctor will request a measurement of your blood B12 levels. In a healthy adult, an ideal blood Vitamin B12 value is considered to be between 500 and 800 pg/mL.

If this value falls below 200 pg/mL, a clinical diagnosis of deficiency is made, and treatment planning begins immediately. During the diagnostic phase, doctors look not only at the B12 level but also at a complete blood count (hemogram) to check if there is an enlargement in the size of red blood cells (megaloblastic anemia). When necessary, folic acid levels and iron stores are also examined for a comprehensive evaluation.

How Is B12 Deficiency Treated?

The treatment for B12 deficiency is personalized based on the underlying cause and the patient's absorption capacity. If the patient does not have a structural disease in the stomach or intestines that would prevent absorption, and the issue is solely poor nutrition, Vitamin B12 is prescribed as an oral tablet.

However, in individuals who have had stomach reduction surgery, those with pernicious anemia, or those suffering from severe intestinal diseases, oral pills cannot enter the bloodstream effectively. In such cases, Vitamin B12 is administered directly into the body via intramuscular injection (shots). Injection therapy is usually given frequently in the first few weeks; once the stores are replenished, patients switch to monthly maintenance doses. In recent years, sublingual tablets and oral sprays that absorb directly into the bloodstream through the oral mucosa have also been used successfully as alternatives to injections.

Complications and Risk Groups

If B12 deficiency is not treated in time, it can lead to serious, irreversible health problems. Damage to the myelin sheath surrounding nerve cells can cause permanent neuropathy (nerve damage). For advanced nerve damage, loss of balance, and movement disorders, a multidisciplinary treatment process is carried out in coordination with the Neurosurgery department of our hospital.

Pregnant women are a major risk group; B12 deficiency caused by anemia during pregnancy can negatively affect the brain and spinal cord development of the unborn baby, leading to premature birth or even miscarriage. Deficiencies in babies and children can cause intellectual disabilities and stunted growth. In older adults, B12 deficiency can trigger memory problems similar to Alzheimer's or dementia.

When Should You See a Doctor?

Reading your body's signals correctly is critical to preventing permanent damage. If you experience one or more of the following symptoms, you should consult a doctor without delay:

• Continuous, worsening numbness and tingling in the hands and feet.
• Extreme fatigue and exhaustion that prevent you from doing your daily tasks.
• Unexplained memory loss, confusion, and difficulty finding the right words.
• Heart palpitations and shortness of breath felt even while resting.

If acute neurological symptoms arise—such as sudden severe shortness of breath, chest pain, a feeling of fainting, sudden loss of strength on one side of the body, or speech impairment—this requires emergency room intervention. In such a scenario, you must immediately call 112 to request medical assistance.

Diagnosis and Treatment Process at BHT CLINIC

At the Internal Medicine department of BHT CLINIC İstanbul Tema Hastanesi, detailed blood tests and physical examinations for our patients presenting with Vitamin B12 deficiency complaints are rapidly concluded on the same day. If the underlying cause of the deficiency is obesity surgery, stomach disorders, or a neurological problem, a coordinated treatment plan is created with our relevant departments.

Our hospital's 24/7 emergency department offers uninterrupted medical support for sudden severe anemia or neurological complaints. To stop putting off your health and restore your vitamin stores to ideal levels, you can call our contact center or easily book an appointment through our website.

Frequently Asked Questions

Does Vitamin B12 cause weight gain?

No, the belief that Vitamin B12 treatment causes weight gain is a complete misconception. In cases of severe deficiency, patients become anorexic, weak, and exhausted. When the deficiency is treated, the body regains its well-being, energy returns, and appetite simply goes back to its normal level. In fact, since B12 speeds up the burning of carbohydrates, it can even help with healthy weight management.

Who gets B12 deficiency?

It is common in vegans or strict vegetarians, individuals over the age of 50, those who have had stomach reduction surgery, and people with intestinal diseases like celiac. Additionally, people who use stomach-protecting medications or diabetes drugs (metformin) for a long time are also in a high-risk group.

Why does B12 deficiency occur after stomach reduction?

Because a large part of the stomach is bypassed in stomach reduction surgeries, the production of a protein called "intrinsic factor," which enables B12 absorption, decreases. As stomach acid also drops, the vitamins in food cannot mix into the blood. Therefore, it is mandatory for bariatric surgery patients to use supplements.

Are injections or pills more effective for B12 deficiency?

This depends on the cause of the deficiency. If there is no absorption problem in the stomach or intestines, pills or sublingual sprays are sufficient. However, for patients who have had stomach surgery or have severe absorption disorders, pills will not work, so intramuscular injection therapy must be applied.

Is an excess of Vitamin B12 harmful?

Because B12 is a water-soluble vitamin, the risk of toxicity or overdose is very low. The body uses what it needs, and the excess is safely excreted from the body through urine.

This article is for informational purposes only; please consult your doctor for diagnosis and treatment.