Vitamin B12 Deficiency Symptoms, Causes & Treatment

Vitamin B12 deficiency is now a raging, worldwide epidemic. From vegans to omnivores, young to elderly, people from the entire demographical spectrum are suffering from it. Just look at the numbers. 39% of the subjects in the Framingham Offspring Study had levels that are borderline deficient.

The tragic thing is, B12 deficiency can easily be misdiagnosed and become absolutely catastrophic. Watch this video if you have the time:

This is no joke we’re talking about. But what is B12 deficiency exactly? What are its symptoms, causes and how the heck do we treat it? Well, here’s your ultimate resource to B12 vitamin deficiency.

What Is Vitamin B12 Deficiency?

Vitamin B12 (aka cobalamin) is of extreme importance. Naturally produced by the gut bacteria of animals that feed on the cobalt of the soil (hence its name), it is essential to our life and health. How essential?

You need it to form red blood cells and grow tissues. You need it for optimized homocysteine levels. You need it to synthesize and repair your DNA and the myelin sheath, a fatty layer guarding your nerves. When nerve fibers aren’t protected — brain, spinal cord and peripheral damage results.

As you can see, B12 is absolutely crucial for maintaining healthy nervous and immune systems. So crucial that a severe vitamin B12 deficiency can lead to permanent nerve damage and psychiatric conditions.

But getting plenty of B12 from food isn’t always enough.

Vitamin B12 must follow a complex pathway of a number of steps for it to be absorbed. Normal function of the stomach, pancreas and small intestine, with their acids and enzymes, are required for proper absorption. Any problem in any step of the pathway may lead to malabsorption, and deficiency.

Chronic stomach inflammation, for example, is often associated with deficiency in B12. The inflammation gives rise to autoimmune reactions that damage the digestive system, often damaging the body’s ability to absorb vitamin B12. Intestinal malabsorption, rather than low dietary intake, can actually explain most cases of deficiency in vitamin B12.

I should also mention that B12 deficiency occurs in four stages. It begins with declining blood levels (stage I), progressing to low cellular concentrations (II), and then to an increased homocysteine levels in the blood and a decreased rate of DNA synthesis (III), and finally macrocytic anemia (IV).

When early scientists discovered B12 deficiency, they concentrated on blood tests. Treatment therefore was a function of the patient’s blood work. But we now know that neurological changes precede hematologic changes. If you wait for anemia to show up, there will already be neurological damage.

This deficiency has been called a “silent epidemic”. It won’t present with severe symptoms at the beginning, but once discovered it may have already caused damage. The nerve system can’t regenerate itself, and once heavy neurological symptoms have kicked in, normal function may not return.

Let’s go through the symptoms and signs of vitamin B12 deficiency.

Vitamin B12 Deficiency Symptoms List

Many symptoms of B12 deficiency are also symptoms of other diseases, so if you have some of them don’t jump off your chair. But the more symptoms you have, the more likely you are to have a deficiency of vitamin B12.

Neurologic Signs and Symptoms of Vitamin B12 Deficiency

B12 deficiency neurological symptoms are the most dangerous, indicating an advanced deficiency. They must be treated with B12 injections urgently, with daily or every-other-day shots until symptoms stop improving. Neurological symptoms of B12 deficiency are:

• Numbness and tingling of the tongue, hands, thighs or feet.
• Difficulty walking.
• Memory loss, forgetfulness, difficulty recalling names or words.
• Disorientation, dizziness, confusion.
• Dementia with or without mood changes.
• Intellectual deterioration.
• Concentration difficulties.
• Abnormal reflexes.
• Balance, coordination and/or speech problems (Ataxia).
• Unsteady walking, falling.
• Tremor.
• Tinnitus, ringing or buzzing in the ears.
• Impaired pain perception.
• Nocturnal cramping.
• Changes in taste and smell.
• Sharp nerve shocks in either side of the body.
• Spinal nerve pain, commonly in the lower back and neck.
• Optic atrophy, visual disturbances, blurred vision, nystagmus, blindness.
• Paralysis.

These symptoms appear because B12 deficiency strips off the myelin sheath that covers cranial, spinal and peripheral nerves. And although progression of neurologic symptoms is gradual, once they have been present for a long time they may not be reversed with treatment.

Neuropsychiatric B12 Deficiency Signs and Symptoms

• Psychosis.
• Hallucinations.
• Delusions.
• Depression.
• Suicidal ideation.
• Mania.
• Anxiety.
• Paranoia.
• Irritability.
• Apathy.
• Personality changes.
• Inappropriate sexual behavior.
• Violent or aggressive behavior.
• Schizophrenic symptoms.
• Sleep disturbances or insomnia.

Hematological Symptoms of Deficiency of Vitamin B12

• Anemia.
• Macrocytosis (large red blood cells).
• Pale skin.
• Dry or cracked sores in the corners of the mouth.
• White spots, usually on the outside forearm skin.
• Hyper/hypo pigmentation of the skin.
• Hyper segmented neutrophils.
• Poor wound healing.
• Breathlessness, asthma, wheezing.
• Chronic fatigue, general weakness.

Gastrointestinal Symptoms of Vit B12 Deficiency

• Loss of appetite, weight loss, malnutrition, anorexia.
• Poor digestion, bloated feeling after eating normal or even small meals.
• Irritable bowel syndrome, constipation, diarrhea.
• Gastric reflux disease.
• Giardiasis (infection of the intestine).
• Inflammation of the pancreas (Pancreatitis).
• Decreased stomach acid.
• Delayed gastric emptying (Gastroparesis).
• Helicobactor pylori infection.
• Small intestinal bacterial overgrowth.
• Malabsorption syndromes like Crohn’s or Celiac disease.
• Liver disease.
• Diphyllobothrium latum (fish tapeworm).

Vascular B12 Vitamin Deficiency Symptoms

• Orthostatic hypotension (low blood pressure when standing up).
• Chest pain.
• Increased heart rate when changing from supine to upright position.
• Heart palpitations.
• Enlargement of the heart.
• Stroke (Cerebral vascular accident).
• Mini stroke (Transient ischemic attack).
• Heart attack (Myocardial infarction).
• Narrowing of the arteries (Occlusive arterial disease).
• Blood clotting, commonly in the legs (Deep vein thrombosis).
• Blockage of an artery in the lungs (Pulmonary embolism).

Any Additional Signs & Symptoms of B12 Deficiency?

Vitamin B12 deficiency also affects the musculoskeletal, endocrinological, immunological, respiratory, genitourinary, and dermatological systems. Other side effects of B12 deficiency that deserve mentioning:

• Increased susceptibility to infections.
• Difficulty swallowing.
• Premature greying, hair loss, dry or lifeless hair.
• Poor antibody production after vaccinations.
• Incontinence.
• Decreased libido.
• Increased urinary tract infections.
• Hypothyroidism.
• Osteoporosis.
• Fractures.
• Muscular spasms and cramps.
• Bleeding from the gums (gingival bleeding).
• Oral ulcers.
• Brittle nails.
• Decreased activity of osteoblasts (cells that build bone).
• Restless legs.
• Weakness of legs, arms, trunk.
• Glossitis, swollen/sore tongue.
• Fainting, lightheadedness.
• Enlarged spleen (splenomegaly) or liver (hepatomegaly).

Special Vitamin B12 Deficiency Symptoms In Men & Women

Vit B12 deficiency symptoms specific for women:

• Infertility.
• Recurrent miscarriage.
• Abnormal PAP smears.
• Intrauterine growth retardation.
• Post-natal depression.

And men:

• Infertility.
• Impotence.
• Low sperm motility.
• Low sperm count.

Signs & Symptoms of Vitamin B12 Deficiency in Infants & Children

• Developmental delay or regression.
• Decreased muscle tone (Hypotonia).
• Poor weight and/or height gain, a general failure to thrive.
• An abnormally small head.
• Intellectual disabilities, lower IQ.
• Language delay or speech problems.
• Poor motor and coordination skills.
• Poor socialization.
• Difficulty in walking or writing.
• Apathy, lethargy, irritability.
• Mood disorders and psychotic behavior (here’s an example).
• Weakness, fatigue, tiredness.
• Tremor.
• Involuntary movements.
• Abnormal sensations.
• Tics.
• Pigmented skin.
• Chronic constipation.
• Epileptic seizures (fits).
• Vision abnormalities.
• Anorexia, loss of appetite or other eating disorders.
• Severe food allergies or sensitivities.
• Anemia.
• Stroke.
• Rooting reflex kept for more than 4-6 months of age.
• A diagnosis of Celiac, thyroid disorder or other autoimmune diseases.
• A diagnosis of any neurological, psychiatric or behavioral disorder.

It is critical you educate yourself. Many of the symptoms mentioned are not uncommon (even psychosis and cognitive decline), but doctors and psychiatrists are often not even aware B12 deficiency can cause this. In such cases, you may never be tested for a deficiency. Which brings us to…

Vitamin B12 Deficiency Misdiagnosis

When B12 deficiency starts affecting the nerves, it is often misdiagnosed and its symptoms are blamed on other conditions (sometimes on themselves):

• Alzheimer.
• Parkinson.
• Multiple sclerosis (where myelin is stripped off, much like B12 deficiency).
• Autism.
• Bipolar disorder.
• ADHD.
• Diabetic neuropathy.
• Vertigo.
• Chronic fatigue syndrome.
• Chronic pain disorder.
• Psychosis.
• Functional neurological disorder.
• Schizophrenia.
• Depression.
• Fibromyalgia.
• Myalgic encephalomyelitis.
• Mini-strokes.
• Crohn’s disease.
• Irritable bowel syndrome.
• Optic neuritis.
• Folate deficiency.
• Infertility.
• Hypothyroidism.

But why is B12 deficiency misdiagnosed in first place?

• Extremely poor B12 knowledge among doctors and health care professionals leading to symptomatic people, especially non-elders, not being tested at all. For example, very often a patient complaining about depression will be automatically prescribed antidepressants instead of being tested for B12 deficiency.

• In most countries, the current “normal levels range” for serum B12 is way too low. Symptomatic patients with levels that are in the grey zone (250-450) aren’t treated, even though deficiencies begin to appear in the cerebrospinal fluid below 550 (see this and this). Some places won’t even treat you if your B12 is over 100, which is absolutely insane.

• Serum B12 blood test isn’t reliable. This is because it shows both active and inactive forms of B12. Methylmalonic acid (MMA) and holotranscobalamin tests are much more reliable, yet rarely used.

• Doctors usually wait for enlarged red blood cells and/or macrocytic anemia to be present. But that is the last, advanced stage of B12 deficiency. At this point, some of the damage can’t be reversed.

• Clinicians ignore the neurological effects of B12 deficiency and assume falling or having cognitive degeneration are part of “normal aging”. Therefore, elder adults aren’t screened for deficiency.

• Similarly, B12 screening isn’t included neither for mental health patients nor for pregnant or breastfeeding women, groups that are at real risk of B12 deficiency levels.

• It is assumed meat eaters get enough B12 from their diet, so doctors don’t even bother checking for B12 deficiency.

• Vitamin B12 deficiency symptoms in adults over 65 are very often misdiagnosed because clinicians blame those symptoms on other, coexisting medical conditions.

• Just a speculation, but I’m wondering if the fact that early treatment for B12 deficiency is so cheap compared to late detection — where expensive medications and tests have to be given — has anything to do with doctors being so unbelievably misinformed.

Remember, the effects of vitamin B12 deficiency are gradual and symptoms may take years to develop. And while your signs can always stem from other causes, it is crucial that your doctor rules B12 deficiency out due to the very real potential for misdiagnosis. You have been warned.

Vitamin B12 Deficiency Anemia

Here’s what happens when you experience a B12 anemia:

You have low red blood cell count or hemoglobin, that red pigment in your blood that carries oxygen and makes it red. Because you’re deficient, your skin becomes pale. Your heart tries to make up for that low delivery of oxygen to the tissues by increasing its rate (even palpitate) to pump more blood.

Because of that lack of oxygen, you feel weak and fatigued, the way you’d feel if you were put on the altitudes of Mount Kenya without gradual preparation. You’re absolutely miserable. Even a tiny bit of effort drains your energy.

Does this sound familiar?

This can all happen because of a lack of vitamin B12. Leave it untreated for enough time and the myelin layer around your nerves may be stripped off completely, leaving you with permanent neurological damage.

Wait a second, Reggie! Isn’t that what’s called ‘pernicious anemia’?

Even though pernicious anemia (aka vitamin B12 deficiency anemia) is often used to refer to all cases of anemia resulting from B12 deficiency, technically it should only describe cases resulting from the absence or inhibition of intrinsic factor in the stomach, preventing B12 from being absorbed.

Pernicious anemia is most often due to autoimmune attacks on the cells that produce intrinsic factor in the stomach. Anemia is really just a symptom, the whole condition is just the final stage of a gradual autoimmune inflammation of the stomach called atrophic gastritis.

If this progressive destruction “only” causes a reduced secretion of the acids and enzymes needed to free food-bound B12 (without affecting intrinsic factor), then you technically don’t have pernicious anemia and can treat it with the free crystalline form of B12 (any supplement).

If, however, intrinsic factor was affected, then the only way of treatment is vitamin B12 shots. Pernicious anemia used to be fatal, but injectable B12 bypasses the intestinal absorption, literally giving new life to patients.

That loss of enzymes, acids and intrinsic factor may also be due to surgical removal of any part of the stomach. Which brings up the question…

What causes vitamin B12 deficiency actually?

Vitamin B12 Deficiency Causes

To fully understand the mechanics of this deficiency, you need to know what causes B12 deficiency in first place. There are a few possibilities:

Low intake of B12.

The most obvious of causes of vitamin B12 deficiency. Vegans and vegetarians are especially at high risk, together with their infants and kids. There are no reliable vegan sources of B12, and no vegetarian should live without regular B12 supplementation. Even the Vegan Society supports this.

Other examples are anorexic/bulimic people or the underprivileged who just can’t afford enough B12 rich foods. Some persons have increased demands, like people with hyperthroidsm, chronic hemolytic anemia, multiple myeloma, myeloproliferative disorders, neoplasms, and pregnant women.

Impaired absorption.

This can either be food-bound cobalamin malabsorption (as it often is with elderly patients), an impaired ability to absorb B12 from food (with no problem absorbing it from its free form in supplements) or complete malabsorption (pernicious anemia). These are caused by problems in any of the steps involved in the absorption of B12.

One common cause is atrophic gastritis, a condition where the parietal cells in the stomach are damaged. If intrinsic factor can no longer be produced, you’ll eventually have pernicious anemia and a severe B12 deficiency even if you consume huge amounts of B12.

Other possible causes of malabsorption are H.Pylori Gastritis, a common infection of the stomach, as well as surgical removal of any part of the stomach that may have parietal cells (like in cancers or weight loss surgeries).

Diseases like achlorhydria, the outdated Antrectomy + Vagotomy procedure and a rare genetic disorder called Mucolipidosis type IV can also cause a malabsorption by lowering acid production in the stomach.

Impaired absorption can also arise from the pancreas, where the enzyme that frees B12 from is complex is absent or inhibited. Cystic fibrosis, chronic alcoholism, Zollinger-Ellison syndrome, and pancreatic cancer are all examples for possible contributors.

Problems in the small intestine can also cause malabsorption, because it is where the B12-Intrinsic factor complex is absorbed. That’s where it is freed and attached to Transcobalamin-II to be circulated in the blood for utilization by various organs. Anything wrong in its ileum can cause a deficiency.

In Celiac disease, for example, the lining of the ileum is damaged and cannot take up B12. In Crohn’s disease, the immune system attacks the gastro intestinal tract, affecting literally any of its parts. Surgical removal of the ileum is another obvious example.

Personally? My gut (heh) feeling tells me that the massive consumption of grains, especially those with gluten, has a lot to do with malabsorption syndromes and B12 deficiency being a silent worldwide epidemic.

Parasite infestation or bacteria overgrowth.

Some worms may make their way into our intestines and take up many of the nutrients from our foods, effectively competing with our gut for B12. One common example is fish tapeworm, found around Canada and Alaska. Gastrointestinal parasitic infestation (like Giardiasis) can behave similarly.

Overgrowth of the normally present bacteria in the gut may also lead to B12 deficiency. If your normal gut flora overgrowths, it will start consuming your B12. Bacterial overgrowth may be the result of disease like diverticulosis, where sac-like dilatations form in the gut with bacteria accumulating there.

Medications.

Some drugs interact with B12 and decrease its blood serum levels, either by inhibiting its availability or by causing a greater excretion. The most famous one is Metformin, a drug used widely for the management of diabetes. According to reports, about 30% of the patients (!) taking this drug for a long period eventually develop a B12 deficiency. According to one study:

Long-term use of metformin in DPPOS was associated with biochemical B12 deficiency and anemia. Routine testing of vitamin B12 levels in metformin-treated patients should be considered.

Other problematic drugs are salicylates (aspirin), anti-tuberculosis drug isoniazid, epilepsy drugs phenobarbital, pheytoin and primidone, gout drug colchicine, AIDS drug zidovudine, and drugs that lower the acidity of the stomach (like those given to patients with reflux disease). B12 supplementation in all these patients is necessary.

Also, anyone who is given B12 for the treatment of a deficiency should not be given certain antibiotics (those of the aminoglycoside group, like gentamicin and tobramycin). These decrease the efficacy of B12.

Toxins.

B12 helps remove toxins from the body. Alcohol, for instance, is a toxin, and chronic alcoholism significantly reduces B12 levels in the blood.

Another example is Nitrous Oxide (N20, ‘Laughing gas’), which irreversibly oxidizes the cobalt ion of B12 from its active state to an inactive state, rendering it useless to the body. The effects of prolonged use of N20 (either as anesthesia for surgeries/dental work/etc or as ‘hippy crack’) can have devastating consequences, including rapid neuropsychiatric deterioration.

Another common toxin that wouldn’t do any good to your B12 stores is cyanide in cigarettes. Also, people undergoing chemotherapy are at an increased risk of B12 deficiency and should supplement.

Genetic problems.

As always, there’s also a genetic contributor, at least to some degree. If the genes responsible for B12 metabolism are affected, absorption of B12 could be hampered. Eight such genes have been identified so far.

Maternal deficiency.

Babies born to mothers who were deficient prior to conception or during their pregnancy/nursing may end up deficient themselves. Unlike adults, they have no stores of B12. If a baby is born to and then breastfed by a B12 deficient mother, therapy must be given urgently. The effects of B12 deficiency on children raised on a vegan diet are especially scary. One study finds:

a significant association between cobalamin [b12] status and performance on tests measuring fluid intelligence, spatial ability and short-term memory with formerly vegan kids scoring lower than omnivorous kids in each case … reasoning, the capacity to solve complex problems, abstract thinking ability and the ability to learn. Any defect in this area may have far-reaching consequences for individual functioning.

Vitamin B12 Deficiency Risk Groups

Now that you know what symptoms B12 deficiency can lead to, and because of all the above causes of B12 deficiency, you can see why it’s essential to test the following groups for a deficiency even before symptoms show up:

• Elderly individuals. Around 20-30% of people above 50 develop atrophic gastritis, a disease which reduces B12 absorption, as stated earlier. This is confirmed by numerous studies.

• Children, mostly those with developmental delays. It can take years before a B12 deficiency develops in adults, because our body stores B12 in our organs (especially the liver). Children, in contrast, don’t have rich stores and a deficiency can get very vicious with them, very quickly.

• Pregnant/lactating women. Fetuses and breast-fed infants draw out nutrients from their mothers. These women should be taking extra B12.

• Vegetarians/vegans. Vegetarians and vegans consistently show lower B12 levels, with estimates that up to 80% of long-term vegans are B12 deficient. Overall, no vegetarian should live without supplementing.

• Those with gastrointestinal surgery. If you had any surgery where a part of your stomach or ileum was removed (including surgeries for weight loss purposes), you’re likely to need a lot more B12 than before.

• People on certain medications. Proton pump inhibitors, H2 blockers, antacids, Metformin, or any other medication which can interfere with B12 absorption. If you take any of these, you should supplement. Those undergoing chemotherapy or using nitrous oxide (laughing gas) regularly should also be supplementing with B12.

• People with a history of eating disorders.

• Anyone with gastrointestinal diseases, Anyone diagnosed with a disease that may cause malabsorption of nutrients, for example Crohn’s, ulcerative colitis, irritable bowel syndrome, and Celiac.

• Anemic people.

• Women with post-natal depression or a history of infertility/multiple miscarriages should be immediately screened for B12 deficiency.

• Heavy smokers or alcoholics.

Vitamin B12 Deficiency Test

So, how do we actually test for B12 deficiency? The most common test is serum B12, the amount of B12 flowing in the blood. This test isn’t optimal.

The first problem I have is that it doesn’t record what’s going on at the cellular level. Second, it records all B12 in the blood, both active (transcobalamin II) and inactive analogues (transcobalamin I and III). Inactive, inaccessible B12 can fictitiously raise our blood level, representing as much as 80% of it.

Another problem is that many countries set the bar way too low, often missing desperately deficient people. Some countries accept levels as low as 100 while people show symptoms on triple that amount. Japan, to their credit, set the lower limit to 500, and their willingness to treat levels considered “normal” in the rest of the world may explain their low rates of dementia diseases.

What’s my solution?

MMA test.

Relax, I’m not going to send you on a Mixed Martial Arts duel with Conor McGregor. I’m talking about methylmalonic acid. You may be able to order a test as a follow-up to a blood test showing B12 in the lower end of the normal range. MMA is a much more accurate test (often the confirmatory, with 99% accuracy!) in indicating a vitamin B12 deficiency.

But what exactly is MMA?

Methylmalonic acid is a substance necessary for your metabolism and energy production. One of the benefits of B12 is that it helps the conversion of one of its forms, methylmalonyl CoA, to succinyl Coenzyme A. If you’re deficient in B12, then MMA levels begins to rise in both the blood and urine.

MMA test may be ordered by itself or along with a test for homocysteine, an amino acid produced by the chemical conversion of methionine. It may rise to toxic levels if B12, B6, B9 (folate) and magnesium are low, and even moderately elevated homocysteine levels are a strong risk factor for many diseases.

If MMA tests aren’t available at your clinic, you may order a private urinary MMA test through Dr. Eric Norman’s site (founder of the uMMA test). If you’re going for uMMA, opt for less than 3.60 mmol/mol creatinine. If you’re going for a serum MMA test, opt for less than 0.04 nmol/mL.

Also, ask your doctor to test for folate (vitamin B9), ferritin (iron storage), and do a full blood count. The important of this can’t be stressed enough, because B12 and folate need each other and a healthy level of iron is crucial.

The Shilling Test

This test is done to find the cause of your B12 deficiency after it had been confirmed through the uMMA/serum B12 test. You’ll be given B12 and its excretion will be checked in the urine, and you’ll then have to go through a couple of testing stages until your doctor finds out the cause of your deficiency (stomach/pancreatic issues, bacterial overgrowth, pernicious anemia, etc).

Do know that many places have stopped performing the Schilling test, because B12 injections are inexpensive, safe, and are the preferred treatment for most B12 deficiency causes anyway.

Vitamin B12 Deficiency Treatment

Treating B12 deficiency early on can often completely reverse symptoms. However, if diagnosed late, neurological symptoms like dementia and other nerve injuries are typically irreversible. According to this study:

There may be a time-limited window of opportunity for effective intervention in patients with cognitive dysfunction and low serum cobalamin.

Let me repeat:

The earlier you treat your deficiency, the more likely you are to avoid permanent damage.

But how exactly do you treat B12 deficiency?

Well, it depends.

Can your body absorb B12 through the stomach? Then any B12 supplement will work. Tablets, sprays, gel, anything. Do you have food-bound cobalamin malabsorption? Then high-dose oral/nasal administration may be effective. Do you lack intrinsic factor entirely (pernicious anemia)? You’ll most probably need B12 injections for life. No other supplement should be used in that case.

Still haven’t identified the culprit of your B12 vitamin deficiency?

Then don’t waste time and just use the injections. Your myelin coating is being stripped off and your nerve protection is deteriorating. Regardless of what’s causing your deficiency, B12 shots are always the superior way to replenish your stores rapidly. They’re very safe, and you can’t overdose on B12.

Also, regardless of the cause, someone very deficient should still inject, at least in the beginning. Yes, oral tablets will raise your serum B12 levels, but they might not affect cellular levels and repair nerve damage. You can’t take that risk and you need to build up B12 levels fast. High-dose methylcobalamin B12 injections are the most efficient way of delivering B12 into the tissues.

And remember, prevention is the best treatment for vitamin B12 deficiency. The greatest tragedy is how cheap and easy early treatment is compared to the consequences. So the next time you feel unbelievably tired, remember it might not be just “aging”. It could be a B12 deficiency. Go test yourself.

P.S. If you want to learn more about B12 deficiency in a fun way, I recommend the movie Sally Pacholok, which you can only watch in Vimeo. Based on the true story of Sally and her book “Could it Be B12?”. It’s a great watch:

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That’s it, fellas. Took me a couple of months to compile this resource. If you believe it can be helpful to someone you know, by all means share it with them. And if you have any question, use the comments section below.

This article is part of a larger guide: Vitamin B12.