B12 deficiency: symptoms, causes and who is affected
Vitamin B12 (cobalamin) is needed to form red blood cells, for the nervous system and to convert food into energy. The body stores the vitamin in the liver for several years, which explains why a deficiency only shows up after a long time. Once the stores run out, the symptoms can become pronounced – and sometimes both physical and mental.
What are the most common symptoms of B12 deficiency?
Symptoms vary from person to person and rarely all appear at once. Tiredness and lack of energy tend to show first, since the vitamin is needed for energy metabolism.
- Unusual tiredness and breathlessness on light exertion
- Tingling, numbness or pins and needles in the hands and feet
- Pale or slightly yellowish skin
- A sore, red or smooth tongue
- Dizziness and palpitations
- Poor concentration and forgetfulness
- Low mood or irritability
- Reduced balance and unsteady gait with long-standing deficiency
Nerve symptoms such as tingling and balance problems occur because B12 is needed for myelin, the protective sheath around the nerves. Those symptoms should be taken seriously, since long-standing deficiency can, in rare cases, cause permanent nerve damage.
What causes B12 deficiency?
There are two main routes: you take in too little, or your body does not absorb what you eat. B12 is found almost exclusively in animal foods – meat, fish, eggs, milk and cheese. Diet is therefore a common cause in people who eat few or no animal products.
Absorption requires a substance called intrinsic factor, produced in the lining of the stomach. If stomach acid drops or the lining is damaged, absorption falls. That is why older adults are a risk group – stomach acid naturally declines with age.
B-Komplex contains B12 in its active form alongside the other B vitamins – vitamin B12 contributes to normal red blood cell formation and to a reduction of tiredness and fatigue.
See current price »Who is most often affected by B12 deficiency?
Some groups run a higher risk and may need to keep a closer eye on things:
| Group | Why |
|---|---|
| Vegans and vegetarians | Get little or no B12 from their diet |
| Older adults (65+) | Lower stomach acid means poorer absorption |
| Pregnant and breastfeeding women | Higher requirement for the baby's development |
| People with gut conditions | Coeliac disease, Crohn's and stomach surgery affect absorption |
| Users of certain medicines | Acid-reducing drugs and metformin can lower levels |
If you take medication for heartburn or diabetes over a long period, it is wise to raise the question of B12 with your doctor or pharmacist.
How is a deficiency detected – and when should you get tested?
A standard blood test measures your B12 level. It is sometimes supplemented with tests for homocysteine or methylmalonic acid (MMA), which rise early in a deficiency and can reveal a problem before the B12 value itself drops. If you have several of the symptoms above – book an appointment with your GP.
If you want to understand how the B vitamins fit together, read more about what B vitamins actually do. And if you are planning a pregnancy, the difference between folate and folic acid is worth knowing.
How do you correct a B12 deficiency?
Once a deficiency is confirmed, the cause determines the treatment. If it is dietary, supplements or fortified foods may be enough. If it is due to poor absorption, sprays or injections are sometimes used – that is for the doctor to decide. A daily B-complex is a simple way to cover your needs preventively if you eat little animal produce.
If you want to compare options, see our guide to the best B-complex. Wondering how much you need? Read about B12 dosage per day.
Physical and mental symptoms – two sides of the same deficiency
Many people think of B12 deficiency as purely physical, but the mental signs can appear early. Low mood, irritability, poor concentration and a feeling that your thoughts are sluggish are all part of the picture. That is because B12 is needed for the nervous system and for the production of signalling substances in the brain.
The physical signs usually involve the blood and the nerves. When B12 is lacking, the body produces too few and oversized red blood cells, a form of anaemia called megaloblastic anaemia. That causes tiredness, breathlessness and pallor. The nerve side shows up as tingling, numbness and poorer balance. Recognising both sides makes it easier to seek help in time.
How to build up and maintain good levels
Prevention is about matching your intake to your needs. If you regularly eat meat, fish, eggs and dairy, you usually get enough. The less animal produce you eat, the more important supplements or fortified products such as plant-based drinks with added B12 become.
- Eat B12-rich foods spread across the week rather than all in one go
- Use fortified products if you are vegan or vegetarian
- Take a daily supplement if your diet is uncertain or your absorption is reduced
- Get tested if you have symptoms or belong to a risk group
Once your stores are filled, it takes a long time before they run down again, which makes maintenance easy. A B-complex gives you B12 together with the other B vitamins that work together in energy metabolism.
Foods highest in B12
If you want to get B12 through food, animal sources are the most reliable. The content varies, but a few foods stand out:
| Food | Approximate B12 content |
|---|---|
| Liver (beef) | Very high |
| Mussels and shellfish | Very high |
| Herring and mackerel | High |
| Beef and pork | Moderate to high |
| Eggs and dairy products | Moderate |
| Fortified plant drinks | Varies – check the label |
If you eat fish and shellfish a couple of times a week and a varied diet otherwise, most people get enough. If animal sources are missing entirely, fortified products or a supplement are the way forward.
When should you see a doctor?
The odd tired day is rarely anything to worry about. But some signs suggest you should book an appointment with your GP rather than wait it out.
- Tingling or numbness that persists or spreads
- Marked tiredness, breathlessness and pallor at the same time
- Balance problems or unsteady gait
- Memory lapses or noticeable low mood without an obvious cause
The earlier a deficiency is caught, the easier it is to correct. Your doctor can run a blood test, find the cause and set up the right treatment – sometimes diet and supplements, sometimes something more if absorption is impaired.
Frequently asked questions
How quickly do you notice B12 deficiency?
The deficiency creeps up on you. Because the body stores B12 in the liver for several years, symptoms can take a long time to appear. Once the stores are empty, tiredness, tingling and pallor can develop gradually over weeks to months. That is why regular checks are a good idea for risk groups such as vegans and older adults.
Can you get B12 deficiency as a meat eater?
Yes. Even if you eat meat and fish, your absorption may be reduced – for example with low stomach acid, gut conditions or after stomach surgery. Older adults and people on acid-reducing medication can become deficient despite a good diet. Symptoms should always be investigated with a blood test before drawing conclusions.
Is tiredness always a sign of B12 deficiency?
No. Tiredness has many causes – sleep, stress, iron deficiency and thyroid issues among them. B12 deficiency is one possible explanation, especially if the tiredness comes with tingling, pallor or forgetfulness. A blood test will establish whether B12 is involved or whether the cause lies elsewhere.
Do nerve symptoms from B12 deficiency go away?
Often – if the deficiency is caught and treated in time, tingling and numbness usually subside. With a very long-standing, untreated deficiency there is a risk of permanent nerve damage. Nerve symptoms such as pins and needles and balance problems should therefore be assessed by a doctor fairly promptly rather than waited out.