exhausted man sits on the floor

Can a Vitamin B12 Deficiency Make You Feel Like You’re Dying?

Google search suggests yes.
Share on facebook
Share on twitter
Share on linkedin
Share on email

Fast Facts

  • The symptom of a vitamin B12 deficiency can feel so debilitating that people have described it as feeling as though they’re dying.
  • Common symptoms of a B12 deficiency include fatigue, heart palpitations, headaches, depression, and more.
  • If you are B12 deficient, supplementing can reduce symptoms and help you feel better.

Ask someone with a vitamin B12 deficiency to describe how it feels, and you’re bound to encounter some hyperbole: After all, just as many people Google “B12 deficiency symptoms” as “B12 deficiency feel like i am dying.”

This could have something to do with the fact that the water-soluble B vitamin is vital to, well, vitality. Vitamin B12 is essential for producing red and white blood cells, as well as platelets (colorless blood cells that help blood clot). It also contributes to the health of your immune system: B12 also jacks up the activity of certain immune cells, contributing to your body’s defense against chronic diseases and viral infections (1).

B12 is also a key player in the development and function of brain and nerve cells says Richard Foxx, M.D., a board-certified physician who treats hormonal disorders and nutritional deficiencies.

It makes sense then that if you have low B12 to the point of a deficiency, it can cause a myriad of physical and mental symptom that can make you feel like you have one foot in the grave.

While a B12 deficiency isn’t exactly ideal, it is treatable. Here’s what you need to know about the symptoms of a vitamin B12 deficiency, and how B12 supplements can help you feel like yourself again.

What Are The Signs and Symptoms of a Vitamin B12 Deficiency?

Due to its vague nature, “I feel like I’m dying” isn’t an incredibly helpful way to explain a set of symptoms to your doctor. However, Dr. Foxx understands why patients default to this verbiage: B12 deficiency symptoms, as it turns out, are considered “non-specific,” meaning they’re quite subjective and not exactly measurable, he says. And many symptoms overlap with other conditions.

Symptoms—which can develop slowly over time or come on more quickly—may (or may not) include:

  • Fatigue
  • Weakness
  • Headache
  • Depression
  • Pale skin
  • Heart palpitations
  • Loss of appetite
  • Weight loss
  • Pain, inflammation, and/or soreness in the mouth or tongue
  • Erectile dysfunction
  • Infertility
  • Tingling of the hands and feet
  • Trouble balancing
  • Confusion or memory issues

How low does your B12 have to be to get symptoms?

If a blood test reveals that your total B12 level is lower than 200 picograms per milliliter (pg/mL), you may be diagnosed with B12 deficiency. 

If your B12 levels are in the intermediate range, your doctor may also measure your levels of methylmalonic acid (MMA) and homocysteine, compounds that are elevated when you’re B12 deficient and are more sensitive predictors of deficiency than your serum level of the vitamin.

Why a B12 Deficiency Can Make You Feel Like You’re Dying

If you have a vitamin B12 deficiency—a total vitamin B12 level under 220 pg/mL—the symptoms can come on slowly or quickly, and include headaches, weakness, depression, weight loss, fatigue, pain, inflammation, and more. The symptoms can be severe, and develop rapidly or over time.

What Causes Low Vitamin B12 Levels?

Your body doesn’t actually make B12; you need to get it from food or supplements. Certain circumstances can interfere with your ability to get enough of the vitamin:

Having a restrictive diet

Found in animal products ranging from meat, poultry, eggs, and milk to clams and liver, plus fortified plant-based foods such as breakfast cereal, Vitamin B12 is available in many foods. However, since many of the sources are animal products, those who adhere to a strict vegetarian or vegan diet could come up short on the nutrient.

Difficulty absorbing B12

While it’s true you need to consume vitamin B12 to benefit from it, the truth is that vitamin B12 deficiency often stems from difficulty absorbing the nutrients you eat due to conditions such as celiac disease, Crohn’s disease, thyroid disease, or gastric abnormalities.

Pernicious anemia

This common autoimmune disease impacts the stomach’s ability to produce the protein that helps your intestines absorb vitamin B12, regardless of how much you consume.

Drug interference

A wide range of common medications can mess with your body’s ability to absorb vitamin B12. They include:

  • Antibiotics such as neomycin
  • Diabetes medications such as metformin
  • Gastric acid inhibitors such as the proton pump inhibitors omeprazole (Prilosec) and lansoprazole (Prevacid)
  • Antihistamines and antiacids such as cimetidine (Tagamet) and ranitidine (Zantac)


Getting older can also set you up for a B12 shortage since absorption naturally declines as you age (3). It’s one reason why Foxx recommends supplementation for patients beginning at age 40.

Causes of B12 Deficiency

  • Your body doesn’t actually make B12; you need to get it from food or supplements.
  • Not getting enough dietary B12, having pernicious anemia or conditions where absorption is impacted, and taking certain medications can lead to a vitamin B12 deficiency.
  • Absorption of B12 also naturally declines as you age.

How to Treat B12 Deficiency

The best treatment for a B12 deficiency depends in part on the cause.

Vitamin B12 injections

When absorption is the issue, the best way to get the vitamin B12 your body needs is via injections that bypass the gut. Subcutaneous (under the skin) or intramuscular injections are available via prescription.

Nasal spray 

In those who struggle with B12 absorption, a B12 nasal spray can also deliver large doses of the vitamin directly to your blood stream via the nose. This course of treatment is typically reserved for maintaining B12 levels after injections bring particularly low levels back to normal (2).

Oral supplements

Daily vitamin B12 supplements can be swallowed or dissolved under the tongue.

Because gastric absorption rates are unpredictable compared to vitamin B12 injections, according to Foxx, most oral vitamin B12 supplements provide much more than the recommended amount to account for the discrepancy between the dose you take and benefit from (1). It could take longer for B12 levels to rise if you choose this treatment approach over injections or nasal spray.

What if You Feel Worse After Taking B12?

If you have a B12 deficiency, common sense dictates that supplementation should make you feel better. However, consuming particularly high doses of vitamin B12—that is, more than the recommended 2.4 micrograms per day—could bring about adverse effects that range from headaches, fatigue, weakness, and tingling in extremities to gastrointestinal symptoms such as diarrhea, nausea, and vomiting. (4)

The good news is that despite these symptoms, there’s no actual danger of toxicity since your body will only absorb what it needs, regardless of dosage.

Of course there’s also a chance that your body isn’t absorbing enough B12 to absolve the symptoms of deficiency. A blood test can confirm if absorption is an issue and help your doctor adjust your dose or treatment approach to ensure your B12 levels right themselves.

The Bottom Line

Coming up short on vitamin B12 can make you feel off kilter—and for some, “like you’re dying.” If the symptoms above sound familiar, see a general practitioner to confirm a deficiency or rule out alternative diagnoses. If you are deficient supplementation can clear up symptoms in the majority of cases.