Exhausted? Depressed? Before you do anything else, get your B12 levels checked.

While it’s common and can be deadly, B12-deficiency is almost completely ignored.

Two years ago I was so chronically tired that I started sleeping in the car for two solid hours while my son was in preschool. I had to force myself awake to pick him up. At first, I blamed the broken sleep common to motherhood.

But when I found myself at stop signs wondering if I could safely close my eyes while waiting for the traffic to clear, I knew it was time to see a doctor. Did I have depression? seasonal affective disorder?

It never occurred to me that I had a simple vitamin deficiency.

“Your B12 levels are extremely low,” my nurse practitioner told me after a blood test.

I thought of the constant tiredness, which I’d described to her as feeling like I was dehydrated, like I needed to drink sleep instead of water. I told her how my hands had been going numb, and how I found it hard to keep warm. About my blurred thinking and sluggish speech. It wasn’t just sleep deprivation or depression?

“B12 deficiency can cause all of those symptoms,” she said. “I’m going to put you on weekly shots for a month. Let’s see if that helps.”

The shots did more than help. They brought me to life again. After the first shot, I woke up in the middle of the night zinging with energy. The second shot evened things out, and I felt like I’d spent most of the previous year intoxicated and had only just become sober again.

More common than we think

News articles covering the level of tiredness I experienced point to causes as varied as our work schedules and stress to lack of melatonin and late-night screen time. But current research also shows that 16–25% of the U.S. population suffers from B12 deficiency. Left untreated, the deficiency can cause neurological damage and begin to mimic the symptoms of diseases like Alzheimer’s, multiple sclerosis, even autism.

“The Framingham Offspring Study found that nearly 40% of people aged 26 to 83 years had B12 levels in the ‘low normal’ range,” wrote Sally Pacholok in an article for Pharmacy Times. Pacholok, a registered ER nurse, has been researching B12 deficiency for decades, ever since she started seeing patients in the ER with chronic problems that began to improve after they received B12 shots. ‘Low normal’ is “a level at which many begin experiencing neurological symptoms.”

B12, unlike many other necessary vitamins, is found only in animal products — such as beef, shellfish, and butter — which is why vegans and vegetarians are encouraged to eat cereals and soy products fortified with B12, to decrease their risk of deficiency.

I haven’t been a vegetarian in almost fifteen years, I told my doctor. I eat plenty of foods high in B12, so how could this happen?

It turns out there are a number of other risk factors for B12 deficiency besides a meat-free diet, from malabsorption syndromes, autoimmune diseases, and genetic defects; to chemotherapy, celiac disease, alcoholism, and AIDS. And once the deficiency sets in, it can cause a whole host of problems.

Pacholok notes that early B12-deficient sufferers are often diagnosed with depression. “They have foggy thinking, poor comprehension, generalized weakness, and fatigue.” Numbness or tingling in the hands and feet, neuropathy, and balance and gait problems are common, especially in the elderly.

Almost all were symptoms I’d had when I thought I was just tired or depressed.

Lack of testing and diagnosis

I got in touch with Pacholok after reading her book, Could It Be B12? which I’d come across by chance months after being diagnosed with the deficiency. She told me I was fortunate to have a medical office aware of the possibility. Most doctors simply don’t test for it. How is it, I’d asked her, that this problem, which is so easy to treat, not to mention inexpensive (a B12 shot costs just a few dollars and is water-soluble, meaning extra B12 in your system can’t hurt you), is rarely mentioned?

“There’s a knowledge deficit,” she said. “In the 60s and 70s they used to give the shots regularly. Then some older doctors started diluting B12 with more saline but charge insurance companies the full cost, and it got a bad name.” Pacholok fought her own hospital administration for years to make the B12 test part of standard blood work when patients came into the ER. “They still think of it as a placebo.”

Pacholok has written extensively about the necessity of testing and treating for B12, even for those not exhibiting symptoms like mine. “All cancer patients should be on B12,” she told me, as the body’s supplies can become depleted both from the cancer itself and from the treatment.

And she’s recently written another book about the importance of B12 testing for children, especially those demonstrating developmental delays. “The signs and symptoms of pediatric B12 deficiency frequently mimic those of autism spectrum disorders,” she writes in Pharmacy Times. Left unrecognized or untreated, the deficiency can cause permanent neurological damage.

Before I went on my own B12 journey, I might have been skeptical at the range and severity of symptoms the deficiency covers. But I know first-hand how deeply my mind and motor functions were affected, and how drastic the change was when I started receiving my shots.

Now I tell everyone to ask their doctor to include B12 in their regular checkup. Depression, exhaustion — you never know. It could be B12.

This story was originally published by Reimagine.me.