Ask the Dietitian: Vitamin B12

What is Vitamin B12?

Most vitamins come with two names, and the alternative name for vitamin B12 is cobalamin. It is a water soluble vitamin which means that we do not store it in our bodies (unlike fat-soluble vitamins), and so we need to eat it regularly in the diet to avoid becoming deficient.

What does it do?

Vitamin B12 does a wide range of things within the body, helping with keeping our nervous system healthy, the production of DNA and the formation of red blood cells. If we don’t have enough B12 we are at risk of something called anaemia. As B12 has so many different roles in the body, the symptoms of anaemia can be varied but some examples include tiredness, loss of appetite, headaches, diarrhoea, and muscle weakness. We cannot self-diagnose a B12 deficiency, so if you are worried that your levels are low it is important to contact your GP as they can do a simple blood test to check.

Where to find it?

What makes B12 unique compared to other B vitamins is that it is mainly found in animal products. If you consume eggs and dairy products as part of your vegetarian diet you are likely to be getting enough. If you exclude either of these, a good way to make sure you get enough is to look out for foods that have B12 added, i.e. they are fortified. Many, but not all, plant-based milks and breakfast cereals have added B12, so it is a good idea to check the label to see if your preferred ones are fortified. Nutritional yeast is another product that is often fortified, and Marmite/yeast spread has some B12 in (if you don’t hate it!).

Should I take a supplement?

If you regularly have dairy products or eggs in your diet it is unlikely that you would need a supplement. Similarly, if you have a good intake of fortified B12 foods – for example, fortified milk on your fortified breakfast cereal in the morning, a fortified yoghurt during the day and fortified milk in your tea and coffee – your intake of B12 is likely to be enough.

If you are concerned that you might not be getting enough B12 through your diet alone, the advice is to look for a supplement that provides a minimum of 10mcg a day, but no more than 2mg a day. This will mean checking the label, and avoiding any mega doses. Remember: if you feel you may be deficient, particularly if you have been vegetarian for a long time and don’t routinely include sources of B12, it is a good idea to speak to your GP.

Update (8th March 2024): The original version of this article erroneously stated that readers should look for a B12 supplement that provides a minimum of 10mg a day. This was due to our editing error.

We have now updated the text to reflect that this should read 10mcg. We apologise for this error and thank you to those who contacted us about this!