I'm sleeping well so why am I feeling tired all the time?

GETTING TO THE HEART OF MEDICAL MATTERS

- Dr Rosemary Leonard

I've been feeling tired and low in energy, even though I sleep well. I'm waiting for a GP appointment, but in the meantime, a friend suggested I have a vitamin B12 injection. Would there be any harm in this?

Vitamin B12 plays an important role in the formation of red blood cells, metabolism and nerve function. It is mainly found in meat, poultry, fish and dairy, and is also added to some foods, such as fortified cereals. B12 deficiency is not common, but vegetarians and vegans are more at risk. Taking certain medicines, such as proton pump inhibitors (to treat excess stomach acid) and metformin (for type 2 diabetes), can also reduce the ability to absorb vitamin B12.

Symptoms can include tiredness, a sore mouth and tongue, numbness, and pins and needles. In the past there have been claims B12 might help prevent dementia, or help athletic performance, but there is no evidence to back this up. Similarly there is no evidence that giving B12 injections can help reduce tiredness, unless there is proven B12 deficiency.

So unless your friend had a genuinely low vitamin B12 level, it is likely her improvement after the jab was a placebo effect - she believed it would do her good, but pink water (the colour of the jab) would probably have had the same effect.

Having very high vitamin B12 levels, which can occur after having injections inappropriately, can cause headaches, nausea, diarrhoea, fatigue and weakness, so I suggest you have blood tests to see if low levels of B12 or anything else, such as iron or vitamin D, are contributing.