Vitamin B12 is needed by the body to make red blood cells, according to the NHS.
It's also used to keep the nervous system healthy, and it helps with the production of DNA.
Vitamin B12 deficiency symptoms include headaches, fatigue, and a loss of appetite.
But you could also be at risk of the condition if you have this "annoying" symptom.
Having an eye twitch could be an early warning sign of a vitamin B12 deficiency, warned charity Thyroid Patient Advocacy.
The twitch is usually in just one eye, as opposed to being in both, it revealed.
While it may not hurt or even be unpleasant, it's usually an annoying sign of the deficiency, the charity added.
"If you have any unusual undiagnosed symptoms, perhaps you should consider whether you have a vitamin B12 deficiency," it said.
"B12 deficiency sometimes goes undiagnosed until the symptoms become moderate to severe, although this is not necessarily the fault of the medical profession.
"The symptoms often come on so slowly that a B12-deficient individual may become accustomed to them and not complain until the symptoms become severe.
"Eye twitch, usually in one eye or the other [could be a sign of a vitamin B12 deficiency].
"It can occur on the eyelid or just below the eye. This is not usually painful, just annoying."
You could also be at risk of a vitamin B12 deficiency if you frequently get pins and needles.
Pins and needles are a tingling or prickling feeling in the feet. The tingling may feel stronger when standing up or walking.
It's usually nothing to worry about, and most people get pins and needles at some point in their lifetime. But, it could be a sign of a deficiency if it keeps coming back, or if it lasts for a long time.
Other warning symptoms include a yellowing of the skin, or changes to mobility.
If you're worried that you may be at risk of a B12 deficiency, you could top up on the vitamin by eating more beef, liver, egg, dairy foods, or salmon.
Speak to a GP if you're worried that you may have a vitamin B12 deficiency.
Most cases can be easily treated with vitamin B12 supplements or diet swaps.
Diagnosing the condition early is crucial, as it can lead to heart conditions and temporary infertility on rare occasions.
Return to News Home