Vitamin B12: Essential for Brain, Nerves, and Heart Health

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Along with providing information on whether Vitamin B12 supplements might be right for you, this article also links to Fullscript where you can buy supplements online through Fullscript’s secure healthcare formulary and get free shipping and 20% off the retail price of professional-grade supplements.

Vitamin B12 is an essential nutrient that plays a crucial role in keeping our bodies healthy. It’s critical a healthy nervous system to maintain the protective covering around our nerves, called the myelin sheath. It also helps make DNA and plays a vital part in forming red blood cells, which carry oxygen to every part of our body. Vitamin B12 also works with other B vitamins, such as folic acid and vitamin B6, to control the levels of an amino acid called homocysteine in our blood, which is important for heart health.

And if B12 supplements are right for you, this article will show you the best kind to choose and the best place to buy B12 supplements online. This post will cover the basics on B12 and give you links to lab tests where you can find our your B12 status as well as order the B12 you need.

What Is Vitamin B12?

Vitamin B12, also known as cobalamin, is a water-soluble vitamin that plays a crucial role in several bodily functions. It is essential for maintaining overall health. Since the human body cannot produce vitamin B12, it must be obtained through diet or supplementation.

Some key functions and benefits of vitamin B12 include:

  • Nervous system function: Vitamin B12 is involved in the maintenance of the myelin sheath that surrounds and protects nerve fibers, ensuring proper nerve signal transmission. PMC8294980
    • Dementia Risk: A study of people with dementia showed the prevalence of Vitamin B12 deficiency in dementia was 7.5%. There was a significant improvement in test score following Vitamin B12 supplementation. [PMC8737092]
  • Energy metabolism: Vitamin B12 is essential for the metabolism of proteins, fats, and carbohydrates, providing energy for the body’s daily functions. It is needed for the synthesis of succinyl-CoA, a key molecule involved in the Krebs cycle, which is the process that generates energy (in the form of ATP) in the mitochondria of cells. PMC10778862
  • Homocysteine metabolism: Vitamin B12, along with vitamin B6 and folic acid, helps regulate homocysteine levels in the blood. Elevated homocysteine levels are associated with an increased risk of cardiovascular disease. [PMID: 37495210]
  • Red blood cell formation: Vitamin B12 is necessary for the proper formation and maturation of red blood cells, which transport oxygen throughout the body. PMC7230602
  • DNA synthesis: Vitamin B12 plays a role in DNA synthesis and repair, contributing to the healthy growth and maintenance of cells. PMC10305463

Vitamin B12 is naturally found in animal-based foods such as meat, fish, poultry, eggs, and dairy products. Fortified cereals, plant-based milk alternatives, and nutritional yeast may also contain vitamin B12. Additionally, B12 is available as a dietary supplement in various forms, such as tablets, capsules, and injections.

Vitamin B12 deficiency can lead to anemia, fatigue, neurological disorders, and cognitive impairment. People at risk for B12 deficiency include older adults, vegans, vegetarians, and those with malabsorption issues due to conditions like pernicious anemia or gastrointestinal surgeries.

Health Problems Associated with B12 Deficiency

A lack of vitamin B12 can cause various health problems. One common issue is anemia, which happens when our bodies don’t have enough red blood cells to carry oxygen. People with anemia may feel tired, weak, and short of breath. B12 deficiency can also lead to nerve damage, causing tingling or numbness in the hands and feet, difficulty walking, and memory loss. Over time, low B12 levels can even cause mental health issues like depression, irritability, and dementia. Pregnant women need sufficient B12 to ensure the proper development of their baby’s brain and nervous system. It’s essential to get enough B12 through our diet or supplements to prevent these health problems and maintain overall health. [NBK441923]

Physical Symptoms of Low Vitamin B12

Inadequate levels of vitamin B12 can lead to a variety of symptoms, which can vary in severity depending on the extent of the deficiency. Some common symptoms of inadequate B12 include:

  • Fatigue and weakness
  • Shortness of breath or difficulty breathing
  • Tingling or numbness in the hands and feet
  • Memory loss or cognitive impairment
  • Mood changes, such as depression or irritability
  • Difficulty with balance or coordination
  • Red, swollen tongue or mouth sores
  • Loss of appetite or weight loss

If left untreated, a B12 deficiency can lead to more serious complications, such as nerve damage, anemia, and digestive problems. Therefore, it is important to seek medical attention if you experience any of these symptoms, particularly if they persist or worsen over time. Vitamin B12 levels in the subclinical low-normal range…are associated with Alzheimer’s disease, vascular dementia, and Parkinson’s disease. Vegetarianism and metformin use contribute to depressed vitamin B12 levels and may independently increase the risk for cognitive impairment. Vitamin B12 deficiency (<150 ρmol/L) is associated with cognitive impairment. Vitamin B12 supplements administered orally or parenterally at high doses (1 mg daily) were effective in correcting biochemical deficiency….Conclusion: Low serum vitamin B12 levels are associated with neurodegenerative disease and cognitive impairment. There is a small subset of dementias that are reversible with vitamin B12 therapy.

Cognitive impairment and vitamin B12: a review [PMID: 22221769]

B12 and Fatigue

Research suggests that there is a clear relationship between B12 deficiency and fatigue. Still, there are so many other causes for fatigue that supplementation of B Vitamins is unlikely to be helpful unless the cause of the fatigue is a deficiency of B12. [PMID: 33809274]. So, testing is important.

B12 is involved in the production of neurotransmitters, such as serotonin and dopamine, which are important for mood regulation and cognitive function. A deficiency in B12 can lead to changes in mood and cognitive function, which may contribute to feelings of fatigue and lethargy.

Additionally, low B12 levels can result in a type of anemia with abnormally large red blood cells, which can also lead to feelings of tiredness and weakness.

Order Your B12 Test Online

Although the normal range for vitamin B12 (cobalamin) levels in the blood is typically considered to be between 200 and 900 pg/mL, the optimal range for vitamin B12 levels in the blood is still a topic of debate. Among B12 health experts, there is no clear consensus on what constitutes an “ideal” level. However, some studies suggest that B12 levels above 400 pg/mL (295 pmol/L) may be associated with better health outcomes, particularly in older adults. It is important to keep B12 levels above 500 for optimal brain function. The Vitamin B12 & Folate test from Access Medical Labs (affiliate link) is available through the NutriScape Lab Shop.

If you have a B12 level below the normal range, and you consume animal products that contain B12, it will be very important to consult with a medical provider to rule out a medical cause. Of course, it’s always best to share your labs as you consult with your healthcare provider who can help interpret your results and determine if any further action is needed.

Are You At Risk For Vitamin B12 Deficiency?

If you belong to any of these groups or suspect that you might have a vitamin B12 deficiency, consider getting tested for B12.

  • Vegans and Vegetarians: Vegans and vegetarians top the list for B12 Deficiency risk. Vitamin B12 is generally found in animal products with the exception of brewer’s yeast. It’s easy for lifelong vegetarians to forget to supplement with B12 for a while and have B12 levels slip into the deficiency range. Since these deficiencies can cause very serious and sometimes irreversible cognitive problems, some have even speculated that a percentage of the dementia population is actually suffering from past B12 inadequacy.
  • People taking Metformin or Proton Pump Inhibitors: Some medications, such as proton pump inhibitors (for acid reflux) and metformin (for type 2 diabetes), can interfere with B12 absorption, increasing the risk of deficiency.
  • Older adults: With age, the body’s ability to absorb vitamin B12 from food decreases due to a reduction in stomach acid production, which is necessary for B12 absorption. This can lead to a deficiency even if their dietary intake appears sufficient.
  • People with gastrointestinal disorders: Conditions like Crohn’s disease, celiac disease, or atrophic gastritis can impair the absorption of vitamin B12, increasing the risk of deficiency.
  • People who have had gastrointestinal surgery: Weight loss surgeries or surgeries that remove a part of the stomach or small intestine can reduce the body’s ability to absorb B12.
  • People with pernicious anemia: This autoimmune condition affects the production of intrinsic factor, a protein required for B12 absorption. Without intrinsic factors, the body cannot efficiently absorb B12 from food, leading to deficiency.
  • Pregnant and breastfeeding women: The increased nutritional demands during pregnancy and breastfeeding can lead to B12 deficiency if the mother’s intake is not adequate and she doesn’t take prenatal vitamins.

Food Sources of Vitamin B12.

The RDA estimates that healthy adults 19 years and older need only 2.4 µg of B12 per day to avoid deficiency. Here’s a table listing some common food sources of vitamin B12 and the approximate amount of vitamin B12 they contain.

Food SourceAmount of Vitamin B12 (mcg) per serving
Clams (3 ounces)84.0
Liver, beef (3 ounces)70.7
Trout, rainbow, wild (3 ounces)5.4
Salmon, sockeye (3 ounces)4.9
Tuna, light, canned in water (3 ounces)2.5
Beef, top sirloin (3 ounces)1.4
Cheese, Swiss (1 ounce)0.9
Yogurt, low-fat (8 ounces)1.1
Milk, low-fat (1 cup)1.2
Egg, large (1 whole)0.6
Chicken, roasted (3 ounces)0.3
Nutritional yeast (1 tablespoon)4.4

Methyl-B12 vs. The Non-Methylated Form

Vitamin B12 is available in several forms, with the two most common being methylcobalamin (methylated) and cyanocobalamin (non-methylated). Foods naturally contain the active forms of vitamin B12, primarily methylcobalamin and adenosylcobalamin. These forms are readily used by the body and are found in animal-based products.

Methylcobalamin is the active, methylated form of B12 that is readily used by the body. It plays a crucial role in methylation, a biochemical process involved in the regulation of gene expression. Methylcobalamin also helps in the conversion of homocysteine, an amino acid linked to heart disease, to methionine, which is essential for protein synthesis.

On the other hand, cyanocobalamin, the non-methylated form, is a synthetic version of vitamin B12 commonly found in supplements and fortified foods. It is more stable and less expensive to produce than methylcobalamin. However, before the body can use it, cyanocobalamin must be converted into an active form, such as methylcobalamin or adenosylcobalamin. This conversion process requires additional steps and may be less efficient, especially in persons with specific genetic variations or health conditions that affect B12 absorption and metabolism.

In summary, the methylated form of B12 (methylcobalamin) is more readily utilized by the body, while the non-methylated form (cyanocobalamin) requires conversion into an active form. Some people may benefit from using the methylated form, particularly those with genetic or health factors affecting B12 metabolism. However, it’s important to consult a healthcare professional before making any changes to your supplement regimen.

Is Vitamin B12 Safe?

Vitamin B12 supplements are safe and well-tolerated, even at high doses. Because B12 is a water-soluble vitamin, the body can excrete excess amounts through urine, reducing the risk of toxicity. Adverse effects are rare, and B12 supplements are often recommended for those at risk of deficiency, such as older adults, vegetarians, and people with absorption issues.

What Medicines Have Interactions with B12?

  • Metformin: This diabetes medication may reduce the absorption of vitamin B12 from the gastrointestinal tract, which could lead to a deficiency over time.
  • Proton Pump Inhibitors (PPIs): These are used to treat acid-related conditions and can decrease stomach acid that is necessary for B12 absorption from food, possibly leading to a deficiency with long-term use.
  • H2 Receptor Antagonists: Similar to PPIs, these medications for acid reflux and ulcers reduce stomach acid and can interfere with B12 absorption.
  • Cholestyramine: Prescribed to lower cholesterol, this medication can bind to vitamin B12, limiting its absorption in the body.
  • Colchicine: This gout treatment may interfere with the normal absorption and metabolism of vitamin B12.
  • Antibiotics: Long-term use of certain antibiotics can affect gut flora and, as a result, the absorption of vitamin B12.
  • Nitrous Oxide (Laughing Gas): Commonly used for anesthesia, this gas can oxidize and inactivate vitamin B12, leading to a deficiency, especially with frequent exposure.

Supplement Interactions with Vitamin B12

  • Folic Acid: Large amounts of folic acid can mask the symptoms of a vitamin B12 deficiency, which could lead to neurological damage if the B12 deficiency is not addressed.
  • Vitamin C: High doses taken along with vitamin B12 might destroy the vitamin, especially if the supplements are mixed in a container before ingestion.
  • Potassium Supplements: After starting potassium supplements, some people might experience a decrease in vitamin B12 absorption, especially if their dietary intake is not adequate.

Order B12 Supplements

Why Professionals Choose the Fullscript Formulary

Your health is on the line. Health professionals know that many other online and retail options set a very low bar for quality–sometimes amazingly low. The Fullscript formulary is the most secure online source for the highest quality brands securely sourced to assure freshness and purity. Here’s what makes Fullscript the best:

  • Meticulous vetting of brand quality. Health professionals trust Fullscript to continuously monitor the quality of each item on the platform. Other retailers operate with profit as their highest or only motive when choosing brands. Fullscript cares only about quality and reliability. Unlike discount stores, large online marketplaces, and other retailers you won’t find ingredients sourced from China or other questionable locations or companies.
  • Free shipping over $50 and best prices when you order through Supplement Sciences.
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  • How It Works:
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B12 Supplement Options

Methyl B12

Methyl B12 – 1000 mcg

Methylcobalamin has been shown to encourage healthy cognitive, memory, emotional, and nerve function.

Amount Per Capsule
vitamin B12 …
 1, 000mcg (as methylcobalamin)

Methyl B12 with Intrinsic Factor

People who might benefit from a B12 supplement that includes intrinsic factor typically have conditions affecting the stomach or small intestine that impair the natural production or function of intrinsic factor. Examples:

  • Pernicious Anemia: This autoimmune condition is one of the most common causes of vitamin B12 deficiency due to a lack of intrinsic factor, which is necessary for B12 absorption.
  • Bariatric Surgery: Procedures that alter the stomach can reduce intrinsic factor production and B12 absorption.
  • Gastritis: Chronic inflammation of the stomach lining can lead to atrophy, reducing both acid and intrinsic factor production, essential for B12 absorption.
  • Long-term Antacid Use: Medications that reduce stomach acid can affect intrinsic factor and, in turn, B12 absorption.
  • Pancreatic Insufficiency: Since the pancreas aids in B12-intrinsic factor complex absorption in the small intestine, any condition impairing pancreatic function can affect B12 absorption.

Methyl B12 with Intrinsic Factor and Folate-Progressive Labs

This B12 option contains an ingredient called intrinsic factor, which can improve absorption in people who have trouble absorbing B12 on their own. Intrinsic factor is a protein that is naturally produced by the stomach and is necessary for the absorption of B12 in the small intestine.

When intrinsic factor is included in a B12 supplement, it can help ensure that the B12 is properly absorbed and used by the body. This can be particularly beneficial for older adults or people stomach conditions that might reduce the ability of the stomach to produce intrinsic factor.

Testing-It is considered critical to keep B12 levels above 500 for optimal brain function. Labs can be tested separately, or as a part of a more comprehensive lab test (affiliate links).

B Complex Including B12

As a general principle when choosing vitamin supplements, it is usually a better strategy to choose supplements with a broader set of nutrients that are in balanced to work together. When mixing and matching single nutrient supplements, there is a much greater chance of missing some nutrients while getting excesses of others.

B Complex Vitamins – Vital Nutrients

B-Complex is a balanced high potency B Vitamin complex supportive to the metabolism of protein and fats, the maintenance of muscle tone in the gastrointestinal tract and conversion of carbohydrates into energy.* B-Complex also supports healthy nerve cells and helps promote the conversion of homocysteine, thus supporting heart health.* B-Complex is an important tonifier in times of mild stress and fatigue.* This formula contains the methylated forms of B12 (methylcobalamin) and Folate (Metafolin L-5-MTHF), and the activated form of B6 (pyridoxal 5’ phosphate) – all considered to be the most bioavailable and physiologically active forms for these vitamins.*

supports a healthy nervous system*
maintains healthy protein, fat, and carbohydrate metabolism*
promotes the conversion of homocysteine*
Take 1 capsule per day, or as directed by a healthcare practitioner.

Serving Size: 1 vegetarian capsule

Amount Per Serving
Thiamin … 100mg (as thiamine HCl)
Riboflavin … 25mg
Vitamin B6 … 25mg (as pyridoxine HCl)
Folate Metafolin® … 680mcg DFE (as L-5-MTHF)
Vitamin B12 … 500mcg (as methylcobalamin)
Biotin … 400mcg 1333%
Pantothenic Acid … 200mg (as calcium pantothenate)
Riboflavin 5’ Phosphate … 10mg
Pyridoxal 5’ phosphate … 15mg
Niacinamide … 75mg

Multivitamin Including B12

O.N.E. Multivitamin — Pure Encapsulations

Serving Size: 1 capsule / Dose: 1 per day

Amount Per Serving
Vitamin A … 1,125mcg (as vitamin A acetate and 73% beta carotene)
Vitamin C … 180mg (as ascorbic acid)
Vitamin D … 50mcg (as cholecalciferol) (D3) (2,000 IU)
Vitamin E … 20mg (as d-alpha tocopherol succinate)
Thiamin … 3mg (as thiamin HCl) (B1)
Riboflavin … 3mg (as vitamin B2 and 43% riboflavin 5′ phosphate (activated B2))
Niacin … 20mg (as niacinamide)
Vitamin B6 … 4mg (as pyridoxine HCl and 38% pyridoxal 5′ phosphate (activated B6))
Folate … 667mcg DFE (as Metafolin®, L-5-MTHF) (L-5-MTHF 400 mcg)
Vitamin B12 … 500mcg (as methylcobalamin)
Biotin … 300mcg
Pantothenic acid … 10mg (as calcium pantothenate) (B5)
Iodine … 150mcg (as potassium iodide)
Zinc … 25mg (as zinc citrate)
Selenium … 70mcg (as selenomethionine)
Manganese … 2mg (as manganese citrate)
Chromium … 200mcg (as chromium polynicotinate)
Molybdenum … 75mcg (as TRAACS™ molybdenum glycinate chelate)
Boron … 1mg (as boron glycinate)
Choline … 10mg (as choline bitartrate)
Inositol … 25mg
Coenzyme Q10 sustained-release … 50mg (as CoQ10 and as 18% from MicroActive® CoQ10-cyclodextrin complex)
Alpha lipoic acid … 50mg
FloraGLO® lutein … 3mg
Zeaxanthin … 500mcg
Lycopene … 500mcg

Food First!

Although this article discusses supplements in detail, don’t forget that we are absolutely committed to the “Food First” approach to nutrition. When it comes to your health, the totality of your eating habits far surpasses the impact of individual nutrients or any single supplement you consume. Even though this article doesn’t delve into the broader picture of your overall diet, it’s crucial to keep this element at the forefront of our minds. Your food needs to provide all the vitamins, minerals, fiber, and phytochemicals to nourish your body systems down to the cellular level.

Food choices, rather than supplements, are the most critical factors for a healthy gut microbiome. These trillions of tiny inhabitants in your gut affect your brain waves; they orchestrate your immune system. They possess the power to create molecules that can switch genes on or off and are even capable of synthesizing neurotransmitters. Opting for organic foods and steering clear of plastic packaging (including those labeled BPA-free) is a smart move to limit toxin exposure. The sum of all these parts leads to a powerful conclusion: the ultimate key to your health lies in the quality and balance of the food you consume. Supplements are secondary.

To Sum It Up

Vitamin B12 is essential for many bodily functions, including the production of DNA and red blood cells, as well as proper neurological function. It is found naturally in animal products such as meat, fish, and dairy, but can also be obtained through supplementation. A deficiency in B12 can lead to a variety of symptoms, including fatigue, weakness, and cognitive impairment. Maintaining adequate levels of B12 is critical for health and cognitive function, and supplementation is especially important for vegetarians and vegans who do not consume animal products.


This Article is Not a Substitute for Medical Advice

Dietary supplements are not designed to diagnose, treat, cure, or prevent any disease. The Supplement Sciences website seeks to provide comprehensive access to the most relevant supplement information along with convenient online ordering. We do not provide medical advice and cannot guarantee that every product suggested is completely without risk. Since each person is unique in their health history and medication use, it is important to discuss supplements with your personal physician. Specifically, pregnant women and individuals being treated for cancer or liver or kidney problems must consult their physician about every nutritional supplement they plan to take. People taking medications for the treatment of HIV or with a history of organ transplant must not take supplements without consulting with their physician.


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