Vitamin B12 deficiency: signs, risks, and how to protect your health

While it often makes headlines in relation to plant-based diets, vitamin B12 deficiency is a quiet health issue that can affect anyone. From unexplained fatigue to serious neurological changes, a lack of this essential nutrient can heavily impact your daily life and long-term well-being. Understanding your personal risk factors, recognizing the subtle warning signs, and knowing the most reliable ways to maintain healthy levels are key to protecting your brain function and everyday energy.

Recently, a case of a young student who followed a vegan style diet, made headlines as she died following a lack of B12. Vitamin B12 is an essential nutrient that quietly supports many of the body’s critical important functions. It helps produce healthy red blood cells, keeps the nervous system functioning properly, aids DNA production, and plays a vital role in converting food into energy. Despite its importance, vitamin B12 deficiency is surprisingly common and can affect people of all ages and lifestyles. While those following plant-based diets are among the groups at greater risk, they are far from the only ones who need to pay attention to their B12 intake.

Subtle warning signs: how to spot a B12 deficiency early

One of the challenges with vitamin B12 deficiency is that symptoms often develop slowly. The body stores several years’ worth of the vitamin in the liver, meaning it can take months or even years before low levels become noticeable. When symptoms do appear, they can be vague and easily mistaken for other health conditions.

Persistent tiredness, weakness, pale skin, shortness of breath, dizziness and poor concentration are common early signs, but of course these are all fairly common to numerous causes. As deficiency becomes more severe, neurological symptoms such as tingling in the hands and feet, poor balance, memory problems, mood changes and depression often develop. If left untreated for too long, nerve damage can become permanent, making early diagnosis especially important.

Dietary sources and the root causes of B12 deficiencies

Vitamin B12 is unique because it is naturally found almost exclusively in foods of animal origin, including meat, fish, eggs and dairy products. Unlike many vitamins, it is produced by certain bacteria rather than by plants or animals themselves. For this reason, obtaining adequate vitamin B12 can be more challenging for people who consume little or no animal products, but there are several other factors that can also increase the risk of deficiency.

Beyond diet: malabsorption risk factors and medications

Older adults are particularly susceptible because the stomach produces less acid with age. Adequate stomach acid is necessary to release vitamin B12 from food, so even people who eat plenty of animal products may struggle to absorb enough. Certain digestive disorders, including Crohn’s disease and coeliac disease, can interfere with absorption, as can surgery involving the stomach or small intestine. Some commonly prescribed medications, including metformin for type 2 diabetes and long-term acid-suppressing drugs used to treat heartburn, have also been linked with lower vitamin B12 levels.

Plant-based diets: fortified foods and reliable sources

People who follow vegetarian or vegan diets should also be aware of their vitamin B12 intake. Since reliable natural plant sources are extremely limited, those avoiding animal products need to obtain the vitamin through fortified foods or supplements. Fortunately, this is straightforward and inexpensive. Many breakfast cereals, plant-based milks, meat alternatives and nutritional yeast products are fortified with vitamin B12, making it easier to meet daily requirements.

B12 myths: why seaweed and spirulina aren’t enough

There are also several myths surrounding vitamin B12. Foods such as seaweed, spirulina and fermented products are sometimes promoted as natural plant sources, but the forms of vitamin B12 they contain are often inactive and cannot be relied upon to meet human nutritional needs. Health professionals generally advise against depending on these foods as the sole source of vitamin B12.

Choosing the right vitamin B12 supplements: cyanocobalamin vs. methylcobalamin

For many people, supplements provide the simplest and most reliable solution. Vitamin B12 supplements are widely available and are considered both safe and effective. The two most common forms are cyanocobalamin and methylcobalamin. Cyanocobalamin is the form most commonly used in supplements because it is highly stable and has been extensively studied. Methylcobalamin is one of the active forms used by the body and is also effective, although it may require more frequent dosing.

Daily dosage and how the body absorbs B12

Adults require only small amounts of vitamin B12 each day, but the body absorbs only a proportion of what is consumed in a single dose. This is why many supplements contain much higher amounts than the daily recommended intake. Depending on the product, vitamin B12 may be taken daily or as a higher-dose supplement once or twice a week. Most healthy individuals tolerate these supplements very well, and there is no evidence that excess vitamin B12 causes harm because unused amounts are excreted by the body.

Getting tested: how doctors diagnose low B12 levels

Diagnosing a deficiency usually involves a simple blood test. Doctors may measure serum vitamin B12 levels alongside other markers if results are unclear. A complete blood count may also help identify changes associated with deficiency. Anyone experiencing persistent fatigue, unexplained neurological symptoms or other concerns should seek medical advice rather than assuming low vitamin B12 is the cause. This is sound advice regardless, its too easy these days to self-diagnose.

Effective treatment options: oral supplements and B12 injections

Treatment depends on both the severity of the deficiency and the underlying reason. If poor dietary intake is responsible, oral supplements are often sufficient to restore normal levels. Where absorption is impaired, vitamin B12 injections may be recommended, at least initially. Most people respond well to treatment, particularly when deficiency is recognised early.

Protecting vulnerable groups and long-term prevention

Pregnant and breastfeeding women should also ensure they are meeting their vitamin B12 requirements, as the vitamin is essential for healthy growth and nervous system development in babies. Healthcare professionals can advise on appropriate supplementation where needed.

The good news is that vitamin B12 deficiency is one of the easiest nutritional deficiencies to prevent. A balanced diet that includes reliable sources of vitamin B12, appropriate use of fortified foods where necessary, and supplements for those at higher risk can all help maintain healthy levels. Regular medical check-ups are also valuable, particularly for older adults or anyone with conditions that affect nutrient absorption.

Whether you eat meat, follow a vegetarian diet, or choose to be vegan, understanding your own risk factors and ensuring an adequate intake of this essential nutrient can help protect your energy levels, brain function and overall long-term health. Bon appetit!

The information provided in this column is for educational and informational purposes only, and does not constitute medical advice. It is not a substitute for a professional medical consultation, diagnosis, or treatment. Always seek the advice of your own physician or other qualified health provider with any questions you may have regarding a medical condition.

Dr Marcus Stephan