'I was diagnosed with vitamin B12 deficiency after waking up to the strangest feeling ever - I was terrified'

Another challenging aspect of the condition is its non-specific symptoms, which can be hard to associate with a particular illness.

The deceptively dangerous symptoms of the condition were highlighted by YouTuber Marc Williams, whose life was completely altered after becoming deficient in the vitamin.

He explained: "I've always been extremely active. Basketball. Volleyball. Football. Weight lifting. Running."

Marc's active life was upended after his first signs of trouble emerged suddenly.

"One morning I woke up with a weakened right leg. Strangest feeling ever. I was totally confused," he recalled.

"Then my left leg went weak to the same degree as my right leg. Needless to say, I was terrified."

The symptoms didn't stop there, however, as they eventually spread to the arms, where Marc experienced persistent twitches.

"Strange sensations all over my body," he described. "When I had muscle twitching, it was typically around the base of the forearm near the elbow. For a couple of days, it was underneath my eye, which was really odd."

The patient's condition progressed to peripheral neuropathy, affecting his nervous system.

"My symptoms were continuing to worsen," he explained on his website. "And after seeing 30 doctors and getting nowhere, I decided to take matters into my own hands."

LATEST DEVELOPMENTS

• ‘I beat stage 4 kidney cancer despite being given months to live - my symptoms weren't typical’
• Vitamin B12 deficiency: Signs of nerve damage 'may become permanent' without proper treatment
• Neurologist names 'the worst thing you can do' for blood sugar and sleep before you go to bed

Like many patients, Marc's search for answers proved frustrating. But he eventually began taking sublingual B12 tablets and noticed rapid improvements.

"By day four of being on the sublingual tablets, my symptoms stopped declining. Now they were holding steady," he reported, noting that his treatment plan was further enhanced with vitamin B12 injections.

While vitamin B12 deficiencies are common, patients should always consult a doctor before taking supplements.

The NHS notes that in most cases, a "blood test is carried out seven to 10 days after starting treatment to assess whether treatment is working".