Vitamin B12 helps keep your nerves and red blood cells healthy. Your body can't make it, so it comes from food: meat, fish, eggs and dairy.
Why B12 runs low
- Pernicious anaemia
- The most common cause in the UK. The immune system stops your stomach absorbing B12 from food.
- Diet
- Vegans who don't take a supplement or eat fortified foods can run low. The body stores B12 for 2 to 5 years, so it can take a long time to show.
- Stomach and bowel
- Operations on the stomach, including some weight-loss surgery, and conditions such as Crohn's disease can stop B12 being absorbed.
- Medicines
- Some medicines, including metformin and proton pump inhibitors for heartburn and reflux, can affect how much B12 you absorb.
Signs of low B12 come on gradually. They can include feeling very tired or weak, shortness of breath, headaches, palpitations, pins and needles, a sore red tongue or mouth ulcers, and problems with memory or balance. They have plenty of other causes too, which is why a blood test comes first.