Recognizing Vitamin B12 Deficiency: Symptoms, Causes, and What You Can Do About It

What does vitamin B12 do in your body?

Vitamine B12, also known as cobalamin, is involved in three important processes in your body. It helps produce energy from your food, keeps your nervous system in good condition, and is necessary for the production of red blood cells, the cells that transport oxygen throughout your body.

Your body does not produce B12 itself. It is produced by microorganisms and reaches you through animal products such as meat, fish, eggs, and dairy. Because your body does not build up a large reserve of B12 and needs a small amount daily, a deficiency can occur if the supply through food or absorption in your intestines is not in order for an extended period.

Symptoms of B12 deficiency: what should you look out for?

A vitamin B12 deficiency usually develops gradually, which makes it difficult to recognize. The most common symptoms are:

• Persistent fatigue and a feeling of weakness, even after sufficient rest
• Concentration and memory problems, sometimes described as brain fog
• Tingling or numbness in the hands and feet
• Dizziness and a reduced sense of balance
• Mood changes, such as irritability or gloominess
• Pale or slightly yellowish skin
• A painful or swollen tongue, or mouth ulcers

With a prolonged and untreated deficiency, anemia can also develop. Your red blood cells then become larger than normal but function less effectively, causing oxygen to be transported less efficiently throughout your body. This explains why fatigue is often the first and most persistent sign. Do not ignore the symptoms for too long: the longer a deficiency remains undetected, the greater the chance that the nervous system will sustain damage that will not fully recover.

Who is most at risk of a deficiency?

Not everyone is at the same risk of a vitamin B12 deficiency. A number of groups deserve extra attention:

Vegans and vegetarians. B12 is found almost exclusively in animal products. Those who eat little or no meat, fish, eggs, or dairy get too little through their diet and need supplements or fortified products.

The elderly. As people age, the stomach often produces less stomach acid, and stomach acid is needed to release B12 from food. As a result, absorption decreases, even if the diet itself contains sufficient B12.

People with intestinal complaints. Conditions such as gluten intolerance, Crohn's disease, and ulcerative colitis can disrupt the absorption of B12 in the intestine, as can stomach or intestinal surgery.

Users of certain medications. Antacids (such as omeprazole) and the diabetes medication metformin can reduce B12 absorption with long-term use.

Women who use the contraceptive pill. The pill can lower B12 levels in the blood, which is often overlooked.

Pregnant and breastfeeding women. They have a higher need for B12, among other things for the development of the baby.

Why a supplement is not always enough

If you are already taking B12 but your symptoms do not improve, the problem often is not in the dosing or the quantity you ingest, but with the way your body absorbs it. To get B12 from the intestines into your blood, your body needs a protein called intrinsic factor (IF), which is produced by the stomach. Without sufficient intrinsic factor, you can take as much B12 as you want, but it simply won't reach your bloodstream properly. In the autoimmune disease pernicious anemia, the body structurally produces too little intrinsic factor, resulting in permanently limited absorption through the intestines.

The form of the supplement also makes a difference. Many common supplements contain cyanocobalamin, a stable but synthetic form that must first be converted by the body before it is usable. Methylcobalamin is the form the body can use directly and is therefore more often recommended for a confirmed deficiency. Hydroxocobalamin is usually administered via injection and remains in the body longer; this is often used for a severe deficiency. For those who have difficulty with absorption through the intestines, a tablet under the tongue or nasal spray can offer a solution, because B12 then enters the bloodstream via the mouth and the intestines are largely bypassed.

Finally, B12 does not work on its own. Foliumzuur (also known as folate or vitamin B9), vitamin B6, magnesium, and ijzer are all necessary for proper use of B12. A deficiency in any of these substances can weaken the effect of your B12 supplement, even if your B12 level appears sufficient on paper.

Which foods contain B12? Dietary sources listed

B12 is found primarily in animal products:

• Liver and other organ meats
• Red meat, poultry, and fish
• Shellfish, such as mussels and oysters
• Eggs
• Dairy products, such as milk, yogurt, and cheese

For those who consume sufficient amounts of these products, the risk of a dietary deficiency is low. Plant-based foods naturally contain hardly any B12, with the exception of products specifically fortified with it, such as some plant-based milk substitutes and breakfast cereals. Vegans are therefore almost always advised to take a B12 supplement, even without symptoms, to prevent a long-term deficiency.

How much vitamin B12 do you need per day?

For most adults, 2.8 micrograms of vitamin B12 per day is sufficient, according to the advice of the Health Council and the Nutrition Centre. Pregnant women need slightly more, 3.3 micrograms per day, and breastfeeding women 3.8 micrograms. Those who eat enough meat, fish, eggs, or dairy usually obtain this effortlessly from their diet. Supplements often contain a much higher dosage than this daily requirement, but that is not a problem: your body simply excretes excess B12.

What can you do yourself?

• Pay attention to the form of your supplement. If a deficiency has been confirmed, choose methylcobalamin, or a tablet or spray if you suspect that your intestinal absorption is not optimal.
• Check the accompanying nutrients. Ensure that you also get enough folic acid, vitamin B6, magnesium, and iron, as these work together with B12.
• Are you unsure about absorption via your stomach or intestines? Discuss this with your GP, especially if you use medicines like antacids or metformin long-term.
• Identify the risk groups. Are you a vegetarian, vegan, over 60, pregnant, or do you use the contraceptive pill? Then keep a close eye on your symptoms.
• Do not wait too long with persistent symptoms. Fatigue, tingling, or concentration problems that do not go away are a good reason to have your levels measured before the nervous system is further strained.

When is a blood test useful?

A blood test provides a definitive answer when you suspect that fatigue, tingling, or concentration problems are related to a deficiency, especially if you belong to a risk group or are already using supplements without improvement. The marker vitamin B12 (cobalamin) measures the amount of B12 in your blood and is the starting point when a deficiency is suspected. In case of questionable results, or if you want to detect absorption problems early, the marker folic acid (folate) provides additional insight, because a folate deficiency causes similar symptoms and can amplify the effect of low B12.

Both markers together show whether your symptoms are actually related to these nutrients, or whether something else is going on. That is valuable information before you start experimenting with higher doses of supplements yourself. A blood test can help determine your specific levels.

What is a normal B12 level?

Dutch General Practitioners (NHG) use three zones for B12 blood levels: below 148 pmol/L is considered a deficiency, between 148 and 250 pmol/L is in the grey zone, and above 250 pmol/L the value is considered sufficient. Reference values ​​may vary slightly per laboratory; therefore, always read your result in conjunction with the stated margins.

The grey zone is difficult to interpret: the value is not clearly too low, but also not convincingly sufficient, while symptoms may be present. In that case, an additional test can provide more clarity.

Methylmalonic acid: an additional test in case of doubt

A B12 determination in the blood (serum) shows how much B12 is circulating, but not always whether your cells can actually use enough of it. As a result, the outcome may appear normal, while there is actually a functional deficiency.

Methylmalonic acid (MMA) is a substance that rises in the blood when cells have too little usable B12. It is therefore a more sensitive marker for a functional deficiency, especially with a borderline value or a result in the grey zone. MMA is not routinely included in an initial screening, but can provide additional clarity in case of persistent symptoms or doubt, in consultation with a doctor.

Conclusion

A vitamin B12 deficiency often creeps in unnoticed, with fatigue, concentration problems, and tingling being the most common signs. Because absorption is just as important as intake, a supplement does not always solve the problem, especially if your stomach or intestines are not functioning properly or if you belong to a risk group. Do you recognize the symptoms, or do you belong to a high-risk group? Then have your levels tested before taking further risks with supplements. This way, you will know for sure whether B12 is actually the cause, and you can take targeted action.