Vitamin B12 is an essential nutrient with numerous key roles, such as red blood cell production and nerve signaling. As you get older, your body’s ability to absorb and utilize this important vitamin declines, putting you at greater risk for B12 deficiency and related fatigue, anemia, and neurological problems. As such, it’s essential to understand the importance of vitamin B12, how much you need to get each day, and how you can ensure you’re getting enough. 

In this comprehensive guide, we will cover everything you need to know about vitamin B12, including what it is, why it’s important, how much you need, and if you should consider taking a B12 supplement. 

What is vitamin B12?

Also known as cobalamin, vitamin B12 is a water-soluble vitamin that belongs to the B-vitamin family. It is bound to the protein in food and is the largest and most structurally complicated vitamin we consume [

1

,

2

]. In order to be absorbed by the large intestine, B12 must be released from dietary protein by a combination of saliva, stomach acid, and digestive enzymes [

1

]. 

Functions in the body

Vitamin B12 plays a critical role in numerous bodily functions, such as the development and function of the central nervous system, red blood cell production, and DNA synthesis [

1

]. It also plays a role in producing chemicals that affect mood, emotions, sleep, and other brain functions [

3

]. 

Adequate intake of B12 is also essential for energy production and breaking down

homocysteine

, an amino acid obtained from dietary protein, to make other amino acids your body needs [

1

].

Recommended daily intake of vitamin B12 

The recommended daily intake of vitamin B12 varies depending on age and life stage, ranging from 2.4-2.8 micrograms (mcg) for adults. Specific recommended intakes are as follows [

1

]:

• Adult men and women: 2.4 mcg/day

• Pregnancy: 2.6 mcg/day

• Lactation: 2.8 mcg/day

Personalized supplements made just for you

If you’re curious about your B12 levels,

Elo Health

can help. Our at-home biomarker testing is part of our comprehensive nutrition assessment and helps us provide precise and effective nutrition recommendations just for you. Based on your biomarkers and questionnaire answers, Elo AI will generate the right supplement combinations (with the right doses) for your health needs and goals. 

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Factors that can influence your B12 levels and needs

Several factors can influence your B12 status and needs, including your age, dietary choices, certain health conditions, and medications.

As you age, you absorb less B12 from the foods you eat, which puts older adults at greater risk for B12 deficiency. If you follow a strict vegan or vegetarian diet, you may also find it difficult to get enough B12, as there are limited amounts of B12 in plant-based foods. Pregnant and lactating women also need slightly more B12 to maintain adequate levels and meet the increased demands on the body [

1

].

Other factors that can inhibit B12 absorption and thus increase your needs include pernicious anemia, digestive disorders (like celiac disease, ulcerative colitis, or Crohn’s), gastrointestinal surgery, and prolonged use of certain medications, including gastric acid reducers and Metformin [

1

].

What foods are high in B12?

Foods that are high in B12 include: 

• Animal-based products, including meats (such as beef, pork, and poultry), fish, dairy products, and eggs [

  1

  ]. 

• Fortified breakfast cereals

• Fortified nutritional yeasts

• Fermented foods and certain types of algae and seaweed 

Since vitamin B12 is water-soluble and sensitive to heat, how you cook your food can also impact the amount a food provides. Depending on whether you grill, broil, or simmer meat, 40-60% of B vitamins may be lost in cooking juices and up to 40% lost when roasting meat due to long cooking times at high temperatures [

4

]. 

The good news is, consuming the juices that run off during and just after grilling, broiling, or simmering meat can help you retain between 70-90% of B vitamins, including B12. Additionally, steaming or sautéing meat for a short time without water appears to prevent the loss of heat-sensitive B vitamins [

4

].

Vitamin B12 deficiency

Because the body stores about 1,000-2,000 times as much as the amount typically consumed in a day, B12 deficiency symptoms can take several years to appear [

1

]. Prolonged deficiency can lead to serious health complications, including nerve damage, cognitive decline, and cardiovascular issues. 

Your B12 status can be assessed with a simple blood test. At Elo, vitamin B12 levels below 400 pg/mL are considered low.

Your

homocysteine

levels can be another marker of B12 status since they tend to increase quickly as vitamin B12 levels decline. Homocysteine levels >15 micromol/L may suggest B12 deficiency [

1

].

Symptoms of B12 deficiency

Common signs and symptoms of B12 deficiency include [

1

]:

• Megaloblastic anemia (characterized by large, abnormal red blood cells)

• Glossitis of the tongue

• Fatigue

• Weakness

• Tingling sensations

• Heart palpitations

• Pale skin

• Memory problems

• Mood changes

• Weight loss 

• Infertility 

Treating B12 deficiency

In most cases, vitamin B12 deficiency is usually treated with vitamin B12 injections, since they are administered directly into muscles and bypass gastric and intestinal absorption barriers. However, research has shown that high doses of oral vitamin B12 can also be an effective treatment option for treating B12 deficiency [

1

].

Supplementing with B12

B12 supplements are available in various forms, including pills, dissolving tablets, prescription injections, and nasal gels [

1

,

5

]. 

The bioavailability of oral B12 supplements (meaning, how much you can absorb and utilize) is about 50% higher than B12 obtained from food [

1

]. And since over-the-counter oral supplements are affordable and easily accessible, they may be beneficial for those at risk of or with mild B12 deficiency. 

If you have significant B12 deficiency or pernicious anemia, your doctor will likely prescribe B12 injections, which are almost fully absorbed since they are administered into the muscle and are quickly absorbed into the blood [

1

].

Who should take B12 supplements? 

You should consider taking a B12 supplement if [

1

]:

• You are over the age of 50

• You have been diagnosed with a B12 deficiency or pernicious anemia

• You follow a strict vegan or vegetarian diet or have a limited dietary intake of B12

• You have impaired B12 absorption due to gastrointestinal conditions (including atrophic gastritis, celiac, Crohn’s, etc.) or medications (like Metformin or proton-pump inhibitors)

• You have had gastric or intestinal surgery that can affect the absorption of B12

How much vitamin B12 should I take? 

When it comes to supplementation of vitamin B12, taking 25-100 mcg daily has been shown to help maintain B12 levels in older adults [

5

]. For those with B12 deficiency or significantly impaired absorption, oral doses between 1,000-2,000 mcg may also be appropriate for short periods of time (typically one month) but should be monitored to prevent excessive dosing as B12 levels increase [

2

].

At Elo, our registered dietitians can take the guesswork out of what supplements you need and how much you should take. Learn more about our

personalized supplements

and get started today.

Can you take too much B12?

Vitamin B12 supplementation is considered safe and has no Tolerable Upper Intake Level (UL) due to its low level of toxicity [

1

]. Even when taken at large doses (1,000-2,000 mcg), a B12 overdose is unlikely because the body only absorbs what it needs and will not store excess amounts [

1

,

6

].

How to take vitamin B12

Oral B12 supplements should be taken with water, either with food or on an empty stomach [

6

]. 

B12 side effects

B12 supplements are generally safe and well tolerated but, like any supplement, can have potential side effects and interactions with certain medications. 

High doses of vitamin B12 (1,000–2,000 mcg or more), such as those used to treat a deficiency, might have some side effects, including [

1

,

6

]:

• Headache

• Fatigue or weakness

• Nausea and vomiting

• Diarrhea

• Tingling hands and feet

What is the best B12 supplement?

You can find a multitude of B12 supplements on the market, but not all are created equal. 

Unlike food, supplement regulation is largely in the hands of manufacturers, and FDA approval for supplements is only required when the product contains a new ingredient. As such, the best B12 supplement is one that has been third-party tested for quality and purity.

Learn more about Elo’s rigorous

third-party testing

. 

If you’re confused about how much vitamin B12 you should take, there’s no need to worry. At Elo Health, we take the guesswork out of the equation by using science to recommend the right nutrition and supplements for you. Additionally, you have access to our

Registered Dietitians and Elo Health coaches

to help guide you on your nutrition and health journey.

Your body is unique, and so are your nutrition needs.

Here’s how Elo can help you feel your best

.

Summary

Vitamin B12 is an essential nutrient with crucial roles in the body, including red blood cell production and nerve signaling. As you age, the ability to absorb and utilize B12 declines, increasing the risk of deficiency and related symptoms such as fatigue, anemia, and neurological problems. Certain gastrointestinal conditions and strict vegan or vegetarian diets can also make it difficult to meet your daily needs.

You can increase your intake of B12 by consuming lean meat and poultry, fish, eggs, and dairy products, or by taking a B12 supplement. While B12 supplements are both safe and effective for treating B12 deficiency and maintaining healthy levels as you age, you should look for B12 supplements that have been third-party tested for purity and quality, such as Elo Health’s

smart supplements

.

Disclaimer: The text, images, videos, and other media on this page are provided for informational purposes only and are not intended to treat, diagnose or replace personalized medical care.