Vitamin B complex is a group of eight B vitamins that help your body release energy from food, keep your nerves and skin healthy and make red blood cells; vitamin B12 is the one people are most likely to lack. Most people get enough B vitamins from a varied diet. Vitamin B12 comes mainly from animal foods such as meat, fish, eggs and dairy, so vegans, older adults and people taking metformin or acid-reducing medicines are at higher risk of deficiency: in Malaysian studies, about 28% to 29% of people with diabetes on metformin had low B12. Signs of deficiency include tiredness, a sore tongue, mouth ulcers and pins and needles. More is not always better: high doses of some B vitamins, especially B6, can cause harm.
Vitamin B complex untuk apa? The eight B vitamins
"Vitamin B complex" means a group of eight B vitamins. According to the NHS, they work together to help the body release energy from food, keep the nervous system and skin healthy, and form healthy red blood cells. Many of them cannot be stored in the body, so you need them regularly in your diet.
| Vitamin | What it helps with | Good food sources |
|---|---|---|
| B1 (thiamin) | Releasing energy from food; healthy nervous system | Peas, bananas, oranges, nuts, wholegrain bread, fortified cereals |
| B2 (riboflavin) | Healthy skin, eyes and nervous system; releasing energy | Milk, eggs, mushrooms, plain yoghurt, fortified cereals |
| B3 (niacin) | Releasing energy; healthy nervous system and skin | Meat, fish, wheat flour, eggs |
| B5 (pantothenic acid) | Releasing energy from food | Chicken, beef, eggs, mushrooms, avocado |
| B6 (pyridoxine) | Using energy from protein and carbohydrates; making haemoglobin | Poultry, some fish, peanuts, soya beans, oats, bananas, milk |
| B7 (biotin) | Helping the body make fatty acids | Found at low levels in many foods; gut bacteria also make it |
| B9 (folate / folic acid) | Healthy red blood cells; lowering the risk of neural tube defects in pregnancy | Broccoli, leafy greens such as spinach, peas, chickpeas, kidney beans, fortified cereals |
| B12 (cobalamin) | Making red blood cells; healthy nervous system; releasing energy; using folate | Meat, fish, milk, cheese, eggs, some fortified cereals |
Folic acid is especially important before and during early pregnancy; see our guides to folic acid and folate deficiency. For biotin and hair, see what biotin and MSM do.
Vitamin B12: what it does and how much you need
According to the NHS, vitamin B12 helps the body:
- make red blood cells and keep the nervous system healthy;
- release energy from food;
- use folate.
How much do you need? Different expert bodies set different amounts. Malaysia's Recommended Nutrient Intakes (RNI 2017) adopted the European Food Safety Authority's approach:
| Group | Vitamin B12 (Malaysia RNI 2017) |
|---|---|
| Children 1 to 6 years | 1.5 micrograms a day |
| Children 7 to 9 years | 2.5 micrograms a day |
| Adolescents 13 to 18 years | 4.0 micrograms a day |
| Adults (19 and over) | 4.0 micrograms a day |
| Pregnancy | 4.5 micrograms a day |
| Breastfeeding | 5.0 micrograms a day |
By comparison, the NHS says adults need about 1.5 micrograms a day. Either way, people who eat meat, fish, eggs or dairy usually get enough from food. The body can store vitamin B12 for around 2 to 5 years, so a deficiency caused by diet can take a long time to appear.
Vitamin B12 foods and other sources
Vitamin B12 is found mainly in animal foods. According to the NHS, good sources include:
- meat, such as beef and chicken;
- fish, such as salmon and cod;
- milk and other dairy products, including cheese and yoghurt;
- eggs.
Vitamin B12 is not found naturally in fruit, vegetables or grains. If you are vegetarian or vegan, look for foods fortified with vitamin B12, such as some breakfast cereals, yeast extracts and soy products, and check the nutrition labels. Vegans may need a B12 supplement.
Signs of vitamin B12 deficiency
A lack of vitamin B12 (or folate) can cause vitamin B12 or folate deficiency anaemia, where the body makes large, underdeveloped red blood cells. According to the NHS, symptoms usually develop gradually and include:
- feeling weak or tired;
- shortness of breath, palpitations and headaches;
- a sore or red tongue, sometimes with mouth ulcers;
- loss of appetite, indigestion or diarrhoea;
- problems with vision;
- problems with memory, understanding and judgement.
Vitamin B12 deficiency can also affect the nerves and brain, causing:
- numbness and pins and needles;
- muscle weakness and problems with balance and coordination;
- psychological problems ranging from mild depression or anxiety to confusion.
See a doctor if you have these symptoms. Diagnosis is usually by a blood test, and it is important to treat it early: some nerve problems can become permanent if B12 deficiency is left untreated. Tiredness and breathlessness are also common in iron deficiency; see our guide to kurang darah (anaemia).
Who needs to watch their B12?
According to the NHS, you are more likely to run low on vitamin B12 if you:
- follow a vegan diet, or rarely eat meat, fish or dairy, without fortified foods or supplements;
- have pernicious anaemia, an autoimmune condition that stops the stomach absorbing B12 (more common in women around 60);
- have had stomach surgery, such as a gastrectomy, or have a bowel condition such as Crohn's disease;
- take medicines such as metformin or proton pump inhibitors (acid-reducing medicines often used for gastrik and reflux);
- are older, as it becomes harder to absorb B12 with age.
Metformin in Malaysia. Metformin is one of the most common diabetes medicines. In a study of 205 people with type 2 diabetes on metformin in a Malaysian district, 28.3% had vitamin B12 deficiency, and the risk was higher in those who had taken metformin for more than 5 years. A study of people aged 65 and over on metformin in Perak found 29.4% were deficient. If you take metformin, ask your doctor whether your B12 should be checked, and do not stop your diabetes medicine on your own. See our guide to kencing manis.
Do you need a vitamin B complex supplement?
Most people can get all the B vitamins they need from a varied, balanced diet. A supplement may make sense if:
- you are pregnant or trying for a baby: the NHS recommends 400 micrograms of folic acid a day until 12 weeks of pregnancy;
- you are vegan and do not eat B12-fortified foods;
- a doctor has found a deficiency.
Treating a deficiency. According to the NHS, diet-related B12 deficiency may be treated with daily B12 tablets or injections. If the cause is not diet-related, such as pernicious anaemia, injections are usually needed every 2 to 3 months for life. Folate deficiency is usually treated with folic acid tablets for about 4 months, but your doctor will check your B12 first, because folic acid can hide a B12 deficiency.
If you buy a supplement, choose one registered with the Ministry of Health (see how to verify KKM registration), check the amount of each B vitamin on the label, and tell your doctor or pharmacist about it.
Safe limits: can you take too much vitamin B?
B vitamins are water-soluble, but high doses of some can still cause harm. The NHS gives this advice for supplements:
| Vitamin | NHS advice on supplements |
|---|---|
| B6 | Do not take more than 10 mg a day unless a doctor advises it. 200 mg or more a day can cause loss of feeling in the arms and legs (peripheral neuropathy), which can occasionally be permanent |
| B3 (niacin) | High doses of nicotinic acid can cause skin flushing and, over a long time, liver damage. 17 mg or less of nicotinic acid, or 500 mg or less of nicotinamide, a day is unlikely to cause harm |
| B9 (folic acid) | More than 1 mg a day can hide the signs of B12 deficiency, which can damage the nerves if missed |
| B12 | 2 mg or less a day is unlikely to cause harm |
| B1, B2, B5, B7 | Unlikely to cause harm at 100 mg (B1), 40 mg (B2), 200 mg (B5) and 0.9 mg (biotin) a day or less |
Check the label of any B complex product, avoid taking several products that contain the same vitamins, and ask a pharmacist if you are unsure.
Frequently asked questions (FAQ)
What is vitamin B complex for (vitamin B complex untuk apa)?
Vitamin B complex is a group of eight B vitamins: B1, B2, B3, B5, B6, B7 (biotin), B9 (folate) and B12. Together they help the body release energy from food, keep the nervous system and skin healthy, and make red blood cells. Most people get enough from a varied diet.
What does vitamin B12 do?
Vitamin B12 helps the body make red blood cells, keep the nervous system healthy, release energy from food and use folate. A lack of B12 can cause vitamin B12 deficiency anaemia and nerve problems such as numbness and pins and needles.
How much vitamin B12 do I need a day?
Malaysia's Recommended Nutrient Intakes (RNI 2017) set vitamin B12 at 4.0 micrograms a day for adults, 4.5 micrograms in pregnancy and 5 micrograms when breastfeeding. Other countries set lower figures; for example, the NHS says adults need about 1.5 micrograms a day. People who eat meat, fish, eggs or dairy usually get enough from food.
Which foods are high in vitamin B12?
Vitamin B12 is found mainly in animal foods such as meat, fish (for example salmon and cod), milk and other dairy products, cheese and eggs, as well as some fortified breakfast cereals, yeast extracts and soy products. It is not found naturally in fruit, vegetables or grains.
What are the signs of vitamin B12 deficiency?
Signs include feeling weak or tired, shortness of breath, headaches, palpitations, a sore or red tongue, mouth ulcers, loss of appetite, and problems with memory or concentration. B12 deficiency can also cause numbness, pins and needles, muscle weakness and problems with balance. See a doctor for a blood test, as untreated nerve damage can become permanent.
Who is at risk of vitamin B12 deficiency?
People at higher risk include vegans and some vegetarians, older adults, people with pernicious anaemia, people who have had stomach surgery or have Crohn's disease, and people taking metformin or acid-reducing medicines called proton pump inhibitors. In Malaysian studies, about 28% to 29% of people with diabetes on metformin had low B12.
Can I take too much vitamin B?
Some B vitamins can cause harm at high doses. The NHS advises not taking more than 10 mg of vitamin B6 a day from supplements unless a doctor advises it, as 200 mg or more a day can cause nerve damage. High doses of nicotinic acid (niacin) can cause skin flushing, and more than 1 mg of folic acid a day can hide a B12 deficiency. Taking 2 mg or less of vitamin B12 a day is unlikely to cause harm.
Disclaimer
This article is for general information only and is not a substitute for advice, diagnosis or treatment from a doctor or pharmacist. Health supplements are not intended to diagnose, treat, cure or prevent any disease.
References
- B vitamins and folic acid — NHS
- Vitamin B12 or folate deficiency anaemia: symptoms — NHS
- Vitamin B12 or folate deficiency anaemia: causes — NHS
- Vitamin B12 or folate deficiency anaemia: treatment — NHS
- Recommended Nutrient Intakes for Malaysia (RNI 2017): Cobalamin (Vitamin B12) — National Coordinating Committee on Food and Nutrition, Ministry of Health Malaysia
- Krishnan GD, Zakaria MH, Yahaya N. Prevalence of vitamin B12 deficiency and its associated factors among patients with type 2 diabetes mellitus on metformin from a district in Malaysia. J ASEAN Fed Endocr Soc. 2020;35(2):163-168.
- Chua KW, et al. Vitamin B12 deficiency in metformin-treated community-dwelling older adults with diabetes: a cross-sectional multicentre study in Perak. Malays Fam Physician. 2025;20:79-100.
