Vitamin B12 is part of the Vitamin B complex. It is considered to be a “Painkilling vitamin”. It helps DNA production, cardiovascular support, and energy metabolism. In this post, learn more about Vitamin B12, its functions, causes of deficiencies, as well as foods and other sources so you can better incorporate B12 into your life.

Vitamin B12 is a very important marker to monitor, especially if you haven’t been leading the best lifestyle or you have known chronic health issues.

What is Vitamin B12?

Vitamin B12, also referred to as cobalamin, is a water-soluble vitamin [1].

It contributes to the successful synthesis of DNA, the normal functioning of the nervous system, and the production of energy [2].

The liver is the main site of storage of vitamin B12 in the human body [3]. Humans can obtain vitamin B from dietary sources, fortified foods, and supplements [456].

It can take the form of cyano-, hydroxyl, methyl, and deoxy adenosyl-cobalamin [7].

Cyanocobalamin, the most stable and unnatural form of vitamin B12, is most commonly used in supplements and does not have a direct cofactor role in cellular metabolism.

The most biologically significant forms of vitamin B12 are methylcobalamin and coenzyme B12 (5’-deoxy-5’-adenosylcobalamin) [8, 9].

Vitamin B12 was considered the “Painkilling Vitamin” in some countries as far back as the 1950s [10].

Vitamin B12 Blood Test Normal Range

The normal range for vitamin B12 is between 200 and 900 nanograms per milliliter (ng/mL).

In this case, however, your lab result may be in the reference range, but not actually be in the optimal range. Vitamin B12 even in the ‘normal’ range can be unhealthy and indicate that certain processes in the body aren’t optimal.

Cobalamin helps break down methylmalonic acid (MMA) [11] and homocysteine – hence, high levels of MMA or homocysteine in the blood may indicate a B12 deficiency. Some studies say this is even a better indicator of B12 status than direct B12 measurement [12].

One study in 94 women found that vitamin B12 levels lower than 250 mg/dL increased risk by 3X the likelihood of having a child with birth defects [13].

Vitamin B12 Benefits

1) Pain Relief

Methylcobalamin, a form of Vitamin B12, reduces the clinical symptoms in legs such as paresthesia (an abnormal sensation like tingling or pricking), burning pains, and spontaneous pain [14].

In one study, methylcobalamin significantly improved symptoms, such as pain and prickling sensation, in patients with neck pain [15].

Intramuscular cobalamin injection is effective in alleviating low back pain in patients with no nutritional deficiencies [16].

Cobalamin provides effective pain management for mouth ulcers [17].

Methylcobalamin treatment reduces pain symptoms in neuralgia, diabetic neuropathy, and lower back pain [181920].

Methylcobalamin improves neuropathic pain [21102210].

2) Brain Health

Methylcobalamin (MeCbl) is the most effectively taken form of vitamin B12 in neuronal organelles [10].

Cobalamin may have a role in the prevention of disorders of brain development and mood disorders as well as Alzheimer’s and vascular dementia in the elderly [23].

Supplementation of cobalamin is useful in neuronal regeneration. It also repairs the negative effects of ischemia on neurons [24].

A study on rats with sciatic nerve injuries supports the treatment of peripheral nerve injuries with Cobalamin [25].

B12 also increases the regeneration of axons and promotes neuronal repair [262728].

3) Sleeping Patterns

Cobalamin treatment improves sleep-wake rhythm disorders in human subjects [2930].

It may increase the light sensitivity of circadian rhythms due to decreased melatonin levels [31].

It’s not normal to struggle falling asleep and wake up in the morning feeling more tired than when you went to bed. Biohacking Insomnia attacks sleep issues from every angle including limbic system repair, hormone levels, and circadian rhythm retraining.

4) Depression

In a randomized trial performed on patients with depression and low normal cobalamin levels, cobalamin supplementation improved depressive symptoms [32].

Studies have found that prolonged consumption (several weeks to years) may decrease the risk of depression relapse and the onset of clinically significant symptoms in people at risk [33].

5) Anti-inflammatory

Methyl B12 suppresses cytokine production of T lymphocytes in cells and is speculated to do the same in patients with rheumatoid arthritis [34].

6) Skin

Topical cobalamin is a new therapeutic option in atopic dermatitis. It is well-tolerable and has low safety risks for both adults and children [3536].

7) Pregnancy and Lactation

One randomized clinical trial states that oral cobalamin supplementation with 250 μg/day throughout pregnancy and early lactation elevates maternal, fetal, and breast milk vitamin B12 levels [37].

8) Eye Health

Higher homocysteine and decreased B12 levels have been associated with an increased risk of macular degeneration [38].

One study involved 5,442 women at high risk of cardiovascular disease aged 40 or older, who had been taking B6/B9/B12 for 7 years.

The study found a 34 – 41% decreased risk of macular degeneration when supplementing with B6/B9/B12 may reduce the risk of macular degeneration [39].


B12 (Cobalamin) leads to the production of S-Adenosyl-Methionine SAM, which increases methylation [4041424344].

Vitamin B12 Foods

  • Liver (15X RDI in 3.5oz) [45]
  • Clams [46]
  • Sardines [47]
  • Steak [48]
  • Tuna [49]
  • Trout fillet [50]
  • Salmon [51]
  • Eggs [52, 53]
  • Milk [53]
  • Shellfish [53]
  • Nori [53]
  • Mushrooms [53]

Only fortified nutritional yeast contains vitamin B12.

Vitamin B12 Deficiencies

Negative Effects of Deficiency

The long-term consequences of less severe B12 deficiency are not fully known but may include adverse effects on pregnancy, vascular, cognitive, bone and eye health [54].

Methylcobalamin increases nerve conduction, myelin regeneration, neuron regeneration, and inhibiting pain transmission [21102210].

B12 deficiency in women is associated with infertility and miscarriage [55].

B12 deficiency causes excess homocysteine, which is a proven risk factor for cardiovascular disease [56]. Individuals with B12 deficiency have a higher prevalence of cardiovascular risk factors such as heart failure, stroke, and diabetes [57].

Deficiency of B12 inhibits melanin transfer between melanocytes and keratinocytes, which may cause darkening of the skin. 19% of subjects in one clinical trial manifested skin darkening resulting from cobalamin deficiency [5859].

Vitamin B12 plays an essential role in the production of red blood cells and low red blood cells can indicate a B12 deficiency [60, 61]. Weakness and fatigue can result if your red blood cells are low since you are not getting enough oxygen to tissues.

Since vitamin B12 is important in producing myelin, a deficiency can cause psychiatric and cognitive problems and pins & needles. In one study with 141 patients, 28% of people who had psychiatric symptoms from B12 deficiency didn’t have any signs of anemia [62].

Low levels of B12 have been linked to depression [33] and Alzheimer’s disease and other types of cognitive impairment [63].

Studies have found that prolonged consumption (several weeks to years) may decrease the risk of depression relapse and the onset of clinically significant symptoms in people at risk [33].

B12 deficiency can cause neuropathy or nerve pain [64], either as a result of a lack of oxygen to the nerves or from myelin destruction.

In this study, every patient treated with B12 had an improvement in psychiatric problems (39 of 39). They also improved various blood markers, as well as a 50% decrease in methylmalonic acid and/or homocysteine [62].

In one 7-year-old boy, B12 deficiency from a vegan diet resulted in neurological symptoms [65].

Multiple studies show that B12 deficiency in the elderly can increase the risk of weakness, frailty, and disability, and increase hospital stay [66, 6754, 68].

With regard to bone health, multiple studies show that B12 deficiency can increase the risk of bone fracture and is associated with lower bone mass [54, 69].

In 4 people who didn’t have cognitive symptoms or anemia, a swollen and inflamed tongue with lesions was found to be an early sign of vitamin B12 deficiency [70].

Although rare, vitamin B12 deficiency can cause blurred vision or eye pain. This can occur when an untreated B12 deficiency results in damage to the optic nerve [71].

Susceptible people

About 6% of people in the US aged 60 or older are clinically vitamin B12 deficient, while about 20% have technically “normal” levels (148 – 221 pmol/L), but are far from optimal [72].

Vitamin B12 deficiency increases with age, from about 1 in 20 among people aged 65 – 74 years to 1 in 10 or even greater among people aged 75 years or greater [67].

People at risk of vitamin B12 deficiency include [73, 53]:

  • People on a vegan/vegetarian diet
  • People with anemia
  • Older people
  • People with gastrointestinal disorders, such as Crohn’s disease or celiac disease
  • Those who have had gastrointestinal surgeries

Pregnant women require higher levels of B12 to prevent birth defects (over 300 mg/dL [13]).

Infants born to B12 deficient mothers or receiving deficient amounts of animal-sourced foods are susceptible to deficiency between the ages of 6 – 12 months [74].

Drugs That Increase Risk of Deficiency

Patients with type 2 diabetes who are prescribed Metformin may be at risk for cobalamin deficiency [75].

Proton pump inhibitors or Histamine 2 receptor blockers (Zantac, Tagamet) may lead to b12 deficiency, as a result of poorer B12 absorption [76, 77].

Hormonal birth control (oral contraception and DMPA) usage among female subjects reduced B12 levels [78].


Genes (notably TCN2) related to B12 deficiency are associated with autoimmune gastritis [79].

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