**Updated January 21, 2023
What is Vitamin B12?
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Vitamin B12 is an essential vitamin to vital physiological processes. Its health benefits are undeniably supported by science, and any deficiency must be treated quickly to prevent irreversible harm.
Vitamin B12, known also as cobalamin, is a vitamin naturally produced and found in animal products. It is important to have sufficient vitamin B12 in the body, as it plays an essential role in many processes.
These include things like red blood cell formation, the creation of nerve and brain cells, and DNA production .
The recommended amount of oral Vitamin B12 intake for adults is 2.4 mcg daily, and those that are deficient in this nutrient can take oral vitamin B12 supplements to achieve normal levels [1,2].
What are the benefits of taking Vitamin B12?
There are many benefits to having sufficient levels of B12 in the body. Below, we describe some of the advantages.
Having healthy red blood cells
- Vitamin B12 is necessary for your body to make red blood cells
- Red blood cells are important to carrying and delivering oxygen throughout your body
- When you do not have adequate B12, you may suffer from something known as anemia
- Anemia is when your body does not make enough red blood cells
- This can cause you to feel tired or weak 
Protecting your bones
- Osteoporosis, a condition with weak bones, is associated with vitamin B12 levels
- One study found that osteoporosis was more common in women with low B12 levels compared with women with normal B12 levels
- Likewise, vitamin B12 may be important to your bone health, specifically for older women 
Strengthening your hair, skin, and nails
- Vitamin B12 deficiency can cause problems with your hair, skin, and nails
- Such problems include skin hyperpigmentation (darkening), hair changes, vitiligo (loss of skin pigment), and cracks around your mouth 
- Taking vitamin B-12 supplements can help to improve these conditions
- No evidence currently exists that B12 can improve symptoms of depression
- However, having low B12 levels correlates with an elevated risk of depression
- Therefore, sufficient levels may help to improve your mood 
Preventing vision loss
- Age-related macular degeneration (AMD) is one of the most common causes of vision loss in individuals over the age of 50
- AMD is related to homocysteine, a chemical used to make proteins in the body
- B12 is necessary for proper regulation of homocysteine levels in the body
- Likewise, having sufficient vitamin B12 intake can help you to achieve appropriate homocysteine levels, thereby avoiding problems with your eyesight 
- Increased levels of homocysteine and methylmalonic acid, two substances closely linked to vitamin B12 levels, can lead to impaired myelination
- Myelination refers to the substance that surrounds your nerves and helps to relay signals in your nervous system
- Therefore, low B12 levels are associated with poor cognition
- Normal B12 levels may have a protective effect on your memory 
Increasing energy levels
- Low vitamin B12 levels can cause you to feel low energy
- Additionally, it can decrease your exercise tolerance, causing tiredness and shortness of breath
- Taking vitamin D, therefore, can help with these symptoms 
Protecting your heart
- Vitamin B12 deficiency is linked to a condition known as macrocytosis
- Macrocytosis is a term that describes enlarged red blood cells
- Macrocytosis is a risk factor for coronary disease, heart attack, stroke, and other heart problems
- Normal vitamin B12 levels would help to prevent macrocytosis 
What can happen when you take too much Vitamin B12?
Vitamin B12 at normal doses of up to 1,000 mcg daily should not cause harm.
Per the Institute of Medicine, there is no evidence of adverse effects occurring in healthy individuals who take higher doses of vitamin B12.
It is very difficult to overdose on vitamin B12.
Despite the presumed safety of B12, you should still always check with your doctor before beginning to take any supplement .
What happens when you have low levels of Vitamin B12?
Vitamin B12 deficiency is common. Many of the symptoms of B12 deficiency are very general and overlap with other kinds of conditions.
This can lead providers to miss or even misdiagnose patients who may have a vitamin B12 deficiency.
Below are some common signs and clinical manifestations of B12 deficiency that are often overlooked:
- Tiredness is perhaps one of the most general symptoms an individual can experience, and it can be attributed to many different things
- If you feel drowsy and have low energy, you may suffer from a B12 deficiency. (megaloblastic anemia)
- Your doctor should order labs for vitamin B12, methylmalonic acid, and total homocysteine if you are experiencing such symptoms
- Tingling in the extremities
- When you feel odd sensations in the extremities, such as burning, numbness, or tingling, you may be experiencing neuropathy
- Vitamin B12 is essential to making myelin, a substance that surrounds your nerves
- Myelin allows your nerves to quickly and efficiently relay signals between neurons
- When B12 is deficient, your nerves may not function properly
- This can manifest as odd sensations in the feet, hands, fingers, or toes
- Tinnitus refers to hearing ringing in your ears
- Just as a B12 deficiency can affect your nerves causing neuropathy, it can also cause tinnitus
- Cognitive Impairment (cognitive decline)
- Vitamin B12 is critical for cognitive function, thinking, and mental processes
- If you find that you are having slowed thoughts or memory loss, you may be at risk of vitamin B12 deficiency
- Smooth tongue
- A normal tongue should look bumpy and feel comfortable in your mouth
- A sign of B12 deficiency includes a smooth-looking tongue that feels swollen and too big for your mouth
- Poor appetite and weight loss
- When you do not have enough B-12, you may experience digestive issues such as nausea
- Nausea can lead you to lose your appetite, and over time this can cause reductions in your weight
- When you have clinically low vitamin B12 levels, you may experience signs and symptoms of depression
- In fact, you may check off all the criteria needed for a depression diagnosis
- If you experience changes in your mood, it would be a good idea to get checked for vitamin b12 deficiency before assuming depression
- Trouble walking
- Deficiency in B12 can cause you to walk abnormally or have trouble balancing
- This can also occur in alcoholism, where individuals may have low levels of B12
- If you feel you are getting aggravated more easily than usual, this may be a sign of a vitamin deficiency such as B12 
Who is at risk for vitamin B12 deficiency?
Certain people may have risk factors for vitamin B12 deficiency. These risk factors are outlined in the table below:
Risk Factors For Vitamin B12 Deficiency
|Conditions with low absorption
|Conditions with low intrinsic factor*
|Conditions relating to low intake
|Prolonged use of certain medications
|Transcobalamin II deficiency
Age greater than 75 years
Vegans or strict vegetarians
|Histamine H2 blocker use for more than 12 months
Metformin use for more than 4 months
Proton pump inhibitor use for more than 12 months 
Should you take Vitamin B12 every day?
If you are deficient in vitamin B12, you can take a vitamin B12 supplement daily.
However, do not start taking any vitamins or supplements without first consulting your doctor.
How does your doctor test for Vitamin B12 and what is the normal range?
Typically, experts do not recommend that doctors do routine screening for vitamin B12 deficiency.
If you have certain risk factors, such as being older than 75 years of age, screening may help identify low B12 levels.
Otherwise, your doctor will likely test your vitamin B-12 levels only if you present with certain symptoms or have certain risk factors .
There are multiple tests that your doctor can perform to check your vitamin B12 levels.
Additionally, several other indicators can help to understand your B12 levels.
To check B12 levels, your doctor will usually perform a complete blood count and obtain a serum vitamin B12 level.
These tests will check:
- Your hemoglobin levels. Hemoglobin is a protein in your red blood cells that helps to transport oxygen
- The size of your red blood cells. As previously mentioned, macrocytosis describes enlarged blood cells, which can cause blood cell dysfunction. Macrocytosis is linked to vitamin B12 levels
- Your blood’s vitamin B12 levels
- Your blood’s folate levels. Both folate deficiency and vitamin B12 deficiency can cause macrocytosis
One shortcoming of vitamin B12 testing is the blood test’s inability to distinguish between active and inactive forms of B12.
Your body can only use active forms of vitamin B12. Therefore, if you have high levels of inactive B12 but low levels of active B12, your labs may return normal .
Consequences of B12 deficiency in older adults
If you are deficient in B12 for an extended period, you may become permanently deficient.
Additionally, deficiency can lead to serious and long-term side effects such as dementia, heart dysfunction, and peripheral neuropathy.
Your risk of B12 deficiency is increased if you are over the age of 50 and if you drink more than one alcoholic beverage daily.
What is the Vitamin B12 dosage for seniors?
Older adults are more likely to be deficient in vitamin B12.
This is because aging causes a decrease in stomach acid and a substance known as intrinsic factor.
Both of these substances are required to absorb B12 from your diet and supplements.
Likewise, up to 62 percent of those over the age of 65 do not have adequate vitamin B12 levels.
Because B12 deficiency is more likely in seniors, experts recommend that those over the age of 50 get their B12 through their diet. Older adults can also take a B12 supplement if necessary.
One study evaluated seniors taking 500 mcg worth of vitamin B12 supplements.
Results found that 90 percent of individuals achieved B12 levels within range.
Likewise, seniors that are deficient in vitamin B12 should start at a supplement dose of 500 mcg. If you are still deficient with this dose, you can try a higher dose of up to 1,000 mcg .
If you have difficulty absorbing oral or dietary B12, or have undergone gastric surgery, your doctor might decide to give you a B12 injection instead.
By doing so, the dose of vitamin B12 circumvents the digestive system and gets absorbed directly in the circulatory system.
Your doctor may get you set up for scheduled vitamin B12 shots until your severe deficiency resolves and you are able to transition to oral B12 supplementation.
What are dietary sources of Vitamin B12?
You can get vitamin B12 from your diet in various ways, but B12 is found primarily in animal products. Potential dietary sources include:
- Meats such as fish, poultry, beef, and clams
- Nutritional yeasts
- Breakfast cereals 
Because vitamin B12 is mostly found in animal products, if you are vegetarian or vegan, you may have low levels of B12.
Who should definitely supplement with B12?
Vegetarians and vegans:
Animal products, such as meat, are rich in vitamin B12 levels.
With a typical diet, animal products can be your main source of vitamin B12.
Therefore, if you are vegetarian or vegan, you may be deficient in B12.
If dietary restrictions do not permit you to eat animal products, you may benefit from taking a supplement to replete your B12 levels.
Those on metformin:
Many people take metformin (Glucophage) because it is indicated for various conditions, including type 2 diabetes, insulin resistance, and polycystic ovarian syndrome (PCOS).
Metformin is a great option for lowering your glucose levels and increasing your body’s sensitivity to insulin.
However, through its mechanism, metformin can also interfere with the absorption of vitamin B12. Over time, you may become deficient in B12 while on metformin therapy.
As aforementioned, a common symptom of B12 deficiency is neuropathy or the tingling sensation in your extremities.
This symptom also occurs in diabetes, yet many diabetic patients will take metformin.
Likewise, doctors may misdiagnose this symptom as diabetic neuropathy when it could be your metformin and B12 levels causing it.
Although metformin increases your risk of B12 deficiency, it is important only to take a supplement if indicated by your doctor.
When taking a supplement like B12, you should do so under the care of your doctor so that they can rule out other causes, monitor your labs, and ensure supplementation is safe.
For example, your doctor can check for drug interactions with a supplement. If you are concerned about your vitamin levels, discuss with your doctor first about getting your B12 levels drawn.
Those with certain conditions:
Certain individuals may have issues absorbing vitamin B12 through their diet, making them deficient. These groups include:
- Certain older adults
- It is common for older adults not to make enough of a substance in the stomach called hydrochloric acid
- Hydrochloric acid helps the body to absorb vitamin B12 from its diet
- Therefore, you may require vitamin B12 supplementation to achieve appropriate levels
- Those with pernicious anemia
- Pernicious anemia is an autoimmune condition where you do not make enough red blood cells
- This is due to trouble absorbing vitamin B12 from your diet and even supplements
- Usually, these individuals will need to receive vitamin B12 injections to normalize their vitamin levels, although oral options may also be effective
- Those with atrophic gastritis
- Atrophic gastritis is an autoimmune condition where individuals do not make enough hydrochloric acid in their stomach
- Similar to what happens with many elderly people, this makes It harder for the body to absorb vitamin B12
- Those who have had certain gastrointestinal (GI) surgeries
- Again, this is usually due to not making enough hydrochloric acid
- Those with certain GI conditions
- These include Crohn’s disease or celiac disease 
Does MTHFR mutation affect Vitamin B12 absorption?
Certain people have a genetic mutation in the gene known as MTHFR, which stands for methylenetetrahydrofolate reductase.
MTHFR is a mutation that occurs in roughly 30 percent of people’s genes, making it incredibly common.
Having this mutation makes it difficult for your body to use B12 how it is supposed to, therefore, you may have difficulty absorbing B12 from your diet.
To use B12, your body needs to methylate the vitamin to create a substance known as methylcobalamin.
Methylcobalamin helps make another substance known as glutathione.
Glutathione is an antioxidant that is necessary to keep your body healthy.
If you have the MTHFR mutation, then your body does not methylate vitamin B12, resulting in glutathione deficiency and causing complications.
People with MTHFR mutations may benefit from taking methylated vitamin B12 .
Which form of Vitamin B12 is the best and why?
Because of the somewhat common incidence of the MTHFR gene mutation in the general population, providers often recommend that everyone who needs to supplement B12 takes a methylated supplement.
Whether you have the MTHFR mutation or not, you can be sure you will benefit from a methylated B12 supplement.
If you are considering purchasing methylated Vitamin B12, I recommend doing so from a reputable and ethical supplement company that fulfills its operations with integrity and transparency.
I have spent a lot of time researching various supplement companies that offer methylated Vitamin B12 and have found one seller that checks off all of my stringent requirements for the supplement’s purity, potency, and the company’s adherence to best practices.
Methyl-Life offers a full range of methylated Vitamin B12 and Folate products. What I like about this company is that its founder has the MTHFR gene mutation and is open about her health struggles on her website.
As always, always consult with your medical provider before starting any supplement. If you get the green light from your provider, I highly recommend purchasing Methyl-Life’s products to supplement your Vitamin B12 and Folate needs. More information about methyl B12 and folate can be found by clicking on the image below:
Click on the image to learn more and order high-quality methylated products
Drugs that interact with Vitamin B12
Vitamin B12 can interact with several medications. If you and your provider decide you should take a vitamin B12 supplement, it is important to be aware of potential drug interactions.
Such drug interactions can affect how your body absorbs B12, putting you at risk for developing a serious deficiency.
Below is a list of drugs and substances that can lower B12 levels in the body:
- Anticonvulsants (e.g., phenytoin, phenobarbital, and primidone)
- Antibiotics (e.g., tetracycline)
- Chemotherapy medications (e.g., methotrexate)
- Colchicine (treats gout)
- Bile acid sequestrants (treat low cholesterol, e.g., colestipol, cholestyramine, and colesevelam)
- H2 blockers (decrease stomach acid, e.g. cimetidine, famotidine)
- Proton pump inhibitors (decrease stomach acid, e.g. esomeprazole, lansoprazole, omeprazole, rabeprazole) 
To understand how some of these drug interactions occur, it is important to understand the role of intrinsic factor and stomach acid in the body.
As mentioned previously in this article, your stomach acid is an important component in absorbing vitamin B12. In food rich in vitamin B12, B12 attaches to proteins contained within the food.
When you eat food and it enters your digestive tract into the stomach, your stomach acid helps to release vitamin B12 from the food or supplement. The absorption of B12 is then facilitated by the intrinsic factor .
The intrinsic factor is a protein found in the stomach. It plays an important role in absorbing and transporting vitamin B12 in the digestive system.
Likewise, because the two are interrelated, not having enough intrinsic factor can cause similar effects to low vitamin B12. Such effects include blood and neurologic problems .
So how does intrinsic factor or stomach acid relate to drug interactions?
Certain substances can decrease acid production in your stomach, affecting your ability to absorb vitamin B12.
For example, drinking alcohol can irritate the lining of your stomach. This can decrease acid production, affecting how vitamin B12 is absorbed.
In fact, research demonstrates that drinking alcohol moderately over a period of eight weeks can decrease your B12 levels .
Knowing these absorption mechanisms, it is easier to understand why some of the medications above can interact with B12.
In addition to alcohol, a number of these medications (e.g., H2 blockers, proton pump inhibitors, etc.) can affect stomach acid production.
If your doctor suggests taking B12, you should always disclose what medications you are on or if you start a new medication.
Your doctor can help you to adjust your medication regimen to optimize B12 absorption.
For example, if you are taking tetracycline, your provider may suggest taking your vitamin B12 and tetracycline at different times of the day.
This is because simultaneous administration of both can affect B12 absorption .
- Vitamin B12 plays several roles within the body, and adequate levels are important to your overall health
- However, vitamin B12 deficiency symptoms can be very general and often diagnosed as other neuropsychiatric disorders or medical conditions
- If you have concerns about being deficient in vitamin B12, you should reach out to your doctor
- Many people, including older adults, those on metformin, or those who do not eat meat, may benefit from B12 supplementation
- However, you should never start a supplement unless it is recommended by your doctor
- If you do decide to start vitamin B12 replacement, take a methylated form starting at 500 mcg daily