'I felt I was stuck in a dream because of a vitamin deficiency nobody talks about.'

“I feel really strange,” I said to my sister over the phone.

“I’m freaking out. I feel as though I’m 20 seconds behind… like I can’t have a proper conversation with anyone because I can’t digest what they’re saying.

“I feel as though I’m stuck in a dream,” I continued, my voice quivering. “Or underwater. And I have no control over it.”

Three weeks ago, I was panicking.

I was fatigued and moody. I found myself struggling to tell a story; I’d start speaking and get confused and tired half way through, as though I couldn’t maintain a coherent train of thought.

At times, I felt drunk without having had a drink.

I wondered if it was vertigo. Or perhaps a middle ear infection that was putting my balance off. I’d been anaemic in the past, so the fatigue was somewhat familiar, but the other symptoms were not.

“Am I going crazy?” I wondered.

I went to the doctor about a very persistent cold that I’d had for weeks, and she suggested a blood test.

Before she told me the results a few days later, she asked me; “So how do you feel at the moment?” and I almost broke down in tears.

As expected, it found I was anaemic, which explained why I was struggling to get to sleep and felt so tired all the time.

But that wasn’t all.

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“Your brain isn’t working at full capacity at the moment,” she explained. “There’s a very good reason why you feel so awful.”

I was seriously deficient in vitamin B12 – something I’d never heard of.

Symptoms include balance issues, mental confusion, pins and needles in extremities, fatigue, mental impairment, depression, irritability, personality changes, feeling faint, ringing in the ears, sore red tongue, mouth ulcers, vision problems and even signs of dementia.

Known as the “energy vitamin”, vitamin B12 helps regulate the nervous system, and helps with the formation of red blood cells that carry oxygen around the body.

Deficiencies are common in people who follow a vegan or vegetarian diet, and therefore don't receive nutrients from animal products like meat, milk, cheese or eggs.

People who suffer from pernicious anaemia, have had part of their stomach or small intestine removed (weight loss surgery), drink heavily, have immune system disorders like Graves' disease or lupus, or suffer from Crohn's disease or coeliac disease, are at a significantly greater risk of suffering from vitamin B12 deficiency. Often identifying the deficiency can lead to a coeliac diagnosis, or a discovery of food intolerance.

I'm not a vegetarian, nor do I have coeliac disease. But when I looked at foods that were high in vitamin B12, they certainly weren't staples of my diet.

They include; clams, beef, turkey, oysters, salmon, liver, fortified cereals and cheese.

RELATED: The tell-tale signs you could have a vitamin or mineral deficiency. 

The doctor prescribed vitamin B12 injections once a week for three weeks. And after my first injection, I was human again.

Within an hour, my mind cleared. I felt liked I'd be injected with 14 hours sleep. I'd woken up from the dream and felt like myself. Rapidly, all my mouth ulcers disappeared.

The Internet is littered with fascinating stories of vitamin B12 deficiencies, some that were misdiagnosed for decades, or mistaken for depression or dementia.

At the end of last month The Sydney Morning Herald published "Doctors called me a too-busy mum - wrong," by Melissa Banigan, which outlined her 20-year-long struggle with the deficiency.

Banigan suffered from headaches, depression, trouble sleeping, peripheral neuropathy, fatigue, a lesion on her spine, vitiligo (a loss of skin pigmentation) and a number of gastrointestinal issues.

Her symptoms worsened. Forgetting where she left the keys, turned into missing deadlines, and forgetting her daughter's date of birth.

One day, Banigan walked into her kitchen and had absolutely no idea where she was. "Feeling sound in neither mind nor body, I was terrified," she writes.

Banigan says her first injection banished the pain she had been living with for her whole adult life, and her brain fog lifted overnight.

Vitamin B12 deficiency is more common for women 60 and over, but can affect men and women of any age.

If any of these symptoms sound familiar, go to your doctor and request a blood test. It could make all the difference.