Vitamin B12 deficiency symptoms: the short answer
The main symptoms of vitamin B12 deficiency are exhaustion and weakness, a sore red tongue, mouth ulcers, pins and needles in the hands and feet, and later problems with balance, concentration and mood [1, 2]. Many people have no clear symptoms for months or even years, so symptoms alone are not proof, and the diagnosis rests on symptoms together with a blood test [2, 6].
At La Rose Clinics in New Maadi, Dr Mohab Ashraf Fouad, a specialist in internal medicine, diabetes, liver and digestive diseases, looks at the symptoms, the likely cause and the tests needed in one visit. If you would like a slot, use the Book your appointment page.
This guide follows a different order from most pages you will find. It starts with the cause (diet, metformin, acid-reducing medicines, surgery, autoimmunity), then the tests that confirm a shortage, then the warning signs you should not wait on. If your question is about tiredness in general rather than B12 specifically, start with the tests for constant tiredness and then come back here.
A symptom map: what happens in the body
Vitamin B12 is needed to make red blood cells and to maintain nerves. That is why the symptoms fall into three groups.
The first group is the blood. When B12 runs low, red blood cells come out larger than normal and do not work well, which causes tiredness, breathlessness on effort, palpitations and headaches [1, 2]. The tongue can become red and sore, the mouth can develop ulcers, and some people also get poor appetite, indigestion or diarrhoea [2, 6].
The second group is the nerves: numbness and pins and needles in the limbs, muscle weakness, problems with balance and walking, and vision problems [1, 2]. Some people lose the ability to feel vibration or to sense where the foot is in the dark, which a doctor can pick up with a simple examination [7].
The third group is mood and memory: low mood, anxiety, poor concentration and slow thinking, and in advanced cases clear confusion or memory decline [2, 6]. Because these symptoms occur in many other conditions, they should not be used alone to make the diagnosis.
One important point is that nerve symptoms can be present while the blood still looks normal. A shortage can affect the nerves without showing up on a blood count, and anaemia can occur without prominent nerve symptoms [1, 6]. That is why a normal blood count does not rule out a deficiency, and the specific test is what settles it.
As for dizziness: it is common when there is anaemia or a balance problem from nerve damage, but it is not specific to B12, and a doctor needs to separate it from other causes such as blood pressure changes, low blood sugar and inner ear problems.
Nerve warning signs you should not wait on
The most serious feature of B12 deficiency is that nerve damage can become permanent if treatment is delayed. The longer the shortage goes on, the more likely it is that some symptoms will not clear completely after treatment [2, 7]. Some nerve symptoms can also linger after the blood level has returned to normal [10].
See a doctor soon if any of the following happens:
1. Persistent numbness or tingling in the hands or feet, especially if it is spreading or moving upwards. 2. Clear unsteadiness when walking, repeated falls, or a feeling that your legs are not with you in the dark. 3. Muscle weakness or difficulty gripping objects. 4. Changes in memory, confusion, or a sudden change in mood or personality. 5. Problems with vision. 6. Loss of control over urine or stool [2].
Any of these signs together with a known risk factor (years of metformin, stomach surgery, a strict plant-based diet) makes the matter a priority. According to a recent expert review, tiredness alone is not a strong enough sign to raise serious suspicion, but tiredness together with peripheral nerve damage and large red blood cells is a strong signal [10].
It is also worth knowing that when nerve symptoms are present, treatment does not necessarily have to wait for every result to come back, because the delay itself is what harms the nerves [8]. In clear nerve cases closer follow-up is needed, and sometimes referral to a blood or nerve specialist [4].
Sudden weakness of a limb or severe difficulty speaking or moving is an emergency, not a matter for a B12 test in a clinic. Go to the nearest emergency department.
Start with the cause: why does B12 fall?
Most people ask "what should I take?" before they ask "why did this happen?". But the cause decides whether treatment is by food, tablets or injections, and whether long-term follow-up is needed. The common causes are as follows.
First, little animal food. B12 comes from meat, fish, eggs and dairy. Someone who rarely or never eats them, or follows a plant-based diet without supplements, is at risk, but body stores last roughly two to five years, so symptoms arrive late [3]. If your diet is plant-based, read B12 in plant-based eating.
Second, metformin. This is one of the most common diabetes medicines, and over time it can interfere with B12 absorption [3, 7]. In a 2025 study of 205 adults with type 2 diabetes taking metformin in India, 17.1% had a low or borderline level, those with deficiency had been on metformin longer (about 12 to 14 years against 8), and 22% had peripheral neuropathy [9]. The study had no comparison group without metformin, so do not read that figure as your personal risk. More detail is in metformin and vitamin B12. Do not stop a diabetes medicine on your own.
Third, acid-reducing medicines. Proton pump inhibitors (such as omeprazole and pantoprazole) and H2 blockers reduce stomach acid, which is needed to release B12 from food. The risk rises with long use, around a year or more [7]. A 2026 Pakistani study of 255 people who had taken a PPI for at least six months found B12 below 200 pg/mL in 38.6% to 59% depending on the drug, but it had no control group, so it does not prove the medicine was the cause [11]. Read long-term reflux medicines before deciding anything.
Fourth, stomach and gut problems. Atrophic gastritis and pernicious anaemia (an autoimmune condition that blocks absorption) is the best-known cause in the UK, and is more common in women around the age of 60 and with other autoimmune conditions such as vitiligo [1, 3]. Crohn's disease, coeliac disease, and removal of part of the stomach or bowel also matter [3, 6].
Fifth, weight-loss surgery. After a bypass, supplements are needed indefinitely according to clinical guidance [7]. See vitamin monitoring after weight-loss surgery for more.
Sixth, age. Absorption falls after 50, and in the UK about one in ten people over 75 are affected [1, 7].
Less common causes include alcohol and nitrous oxide, or laughing gas [3, 6].
The tests that confirm a shortage and how to read them
The basic test is a complete blood count (CBC) together with a serum B12 measurement. The CBC may show large red cells, but it is not enough on its own, and it can come back normal while the deficiency is present [1, 6]. To understand the blood count better, read anaemia symptoms and the CBC.
For the B12 reading itself, the numbers vary from lab to lab and from guideline to guideline. A value below 150 pg/mL is treated as a clear deficiency in the American family physicians' review [7]. Other sources use different cut-offs, such as below 200 as deficient and 200 to 300 as borderline [12]. There is also a grey zone, roughly 150 to 400 pg/mL, in which the number alone does not settle the question [8]. A recent expert review also warned that some commercial B12 assays perform poorly between laboratories and that many low values can be false positives [10]. So your result has to be read against the reference range of the lab that ran it.
If the level is borderline or normal and suspicion remains, methylmalonic acid (MMA) comes in. It rises early and is more useful for confirmation than B12 alone, and experts regard it as the most specific marker [7, 8, 10]. Homocysteine is another sensitive test, but it also rises with folate and B6 deficiency, kidney disease and an underactive thyroid, so it is less specific [8].
Several things can blur the result:
1. The kidneys: reduced kidney function is the most common reason for a falsely raised MMA [8]. 2. Dehydration, thyroid problems and bacterial overgrowth in the gut [8]. 3. Recent antibiotics can lower MMA [8]. 4. Alcohol, liver disease and some cancers can push the blood B12 reading up falsely [7]. 5. Supplements taken before the test can make the number look normal when it is not.
That is why the test is best done before any B12 is started [8].
If the cause is unclear, the doctor may request antibodies against intrinsic factor or stomach parietal cells, and sometimes a stomach endoscopy [6, 7]. A recent review adds that folate should be assessed alongside B12 because folate deficiency produces the same type of anaemia [10]. When both are low, B12 is replaced before folate to protect the nerves [7].
There is no screening test for everyone: the guidance does not recommend testing every adult without a reason, only those with risk factors or symptoms [7].
Normal B12 ranges, numbness, and a borderline result
A common question is "my B12 is 250, is that normal?". The honest answer is that it depends. With numbness, nerve weakness or risk factors, a borderline number deserves a follow-up MMA test rather than quick reassurance [8, 10]. With no symptoms and no risk factors, the same number may simply be a person's usual level.
Numbness is not always B12. It can come from diabetes (diabetic neuropathy), from pressure on a nerve in the neck or wrist, from other vitamin shortages, or from an underactive thyroid. This is exactly why a doctor looks at the whole picture. A person with diabetes on metformin has two possible reasons for numbness at once, and telling them apart is not something to do at home [9].
Many articles say "start injections and be done with it". The problem is that starting before you know the cause stops you from getting a clean test later, and it can leave you without knowing whether you have a stomach or thyroid condition that needs follow-up. In the other direction, when there are clear nerve symptoms and a borderline number, the guidance says treatment does not have to wait for every result [8].
So the practical rule is this: if the symptoms are mild, do the test first and decide afterwards. If there are nerve symptoms, move quickly and see a doctor.
When are B12 injections needed, and how do tablets differ?
The decision rests on the cause and on whether nerve symptoms are present, not on the number alone. Without mentioning doses, this is the general picture.
Injections are favoured in severe deficiency, in severe nerve symptoms, and in major malabsorption (such as pernicious anaemia, removal of the stomach or part of the bowel), because they bypass absorption from the gut [4, 7, 10]. Sometimes injections are used first and the doctor then decides whether to continue them or move to tablets.
High-dose tablets work often, even in people with absorption problems, because a small fraction is absorbed without intrinsic factor. In a small Cochrane review, high-dose oral treatment was as effective as injections for anaemia and for nerve symptoms, though less effective at normalising MMA [7]. In mild diet-related deficiency, tablets plus a change in diet are often enough [4].
How long treatment lasts differs. If the cause is diet, it may stop once the level is restored and the diet has changed; if the cause is an absorption disease such as pernicious anaemia, treatment is usually lifelong [4, 5]. For people on diabetes or acid-reducing medicines, the level is checked periodically, and the studies recommend interval screening without fixing a set interval [9].
After starting, recovery follows a pattern: MMA, homocysteine and young red cells improve in about a week, anaemia in about 8 weeks, and nerve symptoms over 6 weeks to 3 months [7]. Some nerve symptoms may not recover fully if the damage is old [2, 7].
One safety point: B12 injections only rarely cause itching or hives as an allergic-type reaction [10], and no safe upper level has been established, so it is better to rely on a test than on a guess [10]. Very high blood levels have also been linked in some studies to worse outcomes, which is another reason not to take it without testing [10].
Everyday life in Egypt: food, fasting and work
Traditional Egyptian food has plenty of B12 sources (chicken, meat, fish, eggs, cheese and milk), but some people rely on foul, ta'ameya and koshari for most of the week, whether from circumstances, habit or choice. This is not by itself a sure cause of deficiency, because body stores last for years [3]. Liver stores can delay symptoms by up to about ten years [7].
Long Christian fasting periods without animal products, or a permanent plant-based diet, add to the chance when they combine with another cause (metformin, an acid-reducer, or being over 50). This is a possibility, not a verdict: a short fasting season on its own is not the most likely explanation for a real deficiency.
Ramadan, heat and work shifts explain tiredness for most people: little sleep, dehydration, long hours. But tiredness that continues after those conditions ease, or that comes with numbness or a sore tongue, is the kind that needs checking. Persistent diarrhoea or indigestion may also be the cause of the shortage rather than its result [2, 6].
B12 supplements are easy to get without a prescription, and starting on your own throws away the chance of a clean test [8]. Our advice is a blood count and a B12 test first, then food and treatment according to the cause. If you take regular medicines, photograph the boxes and bring the photos to the visit (see photograph your medicine boxes).
If you also have diabetes, the same visit can be followed up together with your diabetes care so that your whole condition is seen at once.
Common myths and mistakes
Myth one: "the blood count is normal, so B12 is fine". Wrong. A shortage can affect the nerves without anaemia [1, 6].
Myth two: "only vegans get it". Wrong. Metformin, acid-reducing medicines, stomach surgery, older age and autoimmune disease are all important causes [3, 5, 7].
Myth three: "a B12 injection is an energy booster". If the tiredness has another cause (iron-deficiency anaemia, a thyroid problem, poor sleep, low mood), it will not help. This is also why the test comes before the injection. Our page on vitamin drips makes the same point: need is decided by a test.
Myth four: "stop metformin if B12 is low". No. That decision is made with your diabetes doctor, and the usual approach is to treat while the medicine continues, with the level followed up [9].
Myth five: "the lab number is absolute". Laboratories differ, reference ranges depend on the source, and a borderline number needs an MMA [8, 10].
The last mistake is waiting. When numbness is spreading or balance is affected, delay is what turns a treatable problem into permanent damage [2, 7].
The visit at the Maadi branch
If these symptoms or risk factors sound like you, you can see Dr Mohab Ashraf Fouad, a specialist in internal medicine, diabetes, liver, digestive diseases and endoscopy, at the Maadi branch: 14 El-Mokhtar St, off El-Nasr St, behind QNB Bank, New Maadi. Internal medicine and digestive care are available in Maadi only, and the clinic runs on Saturday from 4 to 7 pm. Schedules can change, so we confirm them when you book.
The visit goes like this: we ask about food and medicines (especially diabetes and acid-reducing ones) and any previous surgery, we examine the nerves, balance and tongue, and we choose the right tests. An abdominal ultrasound can be done in the same visit if digestive symptoms call for it. After the results, we settle the cause, the treatment route and the follow-up. Early clinical evaluation helps diagnose vitamin B12 deficiency and start appropriate treatment before any irreversible neurological complications develop [1].
To book, call or send a WhatsApp message on 010 4066 1893, or use the booking page. For any question about cost, send a WhatsApp message. And if you would like to see the service more broadly, look at the internal medicine doctor in Maadi.
