Your body needs vitamin B12 for maintaining metabolism, producing DNA and red blood cells, keeping the nervous system healthy, and more (1, 2).

Fortunately, most people get enough of this water-soluble nutrient from their diet.

However, some groups of people might require more than what they get from food, such as (1, 3, 4, 5):

  • older adults
  • those who are pregnant or breastfeeding
  • those who eat a vegan or vegetarian diet
  • those with digestive issues
  • people taking certain medications

If you fall into any of these categories, you might consider taking a vitamin B12 supplement — and you may wonder if a liquid form is the way to go.

This article reviews liquid vitamin B12’s benefits, side effects, dosage information, and more.

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Naturally occurring vitamin B12 is mostly found in animal foods, including meat, poultry, seafood, eggs, and dairy products. Some grains, like breakfast cereals and nutritional yeast, are also fortified with the nutrient (6, 7).

On the contrary, liquid vitamin B12 supplements are made synthetically in laboratories using microbes and other chemical processes. They’re made by combining the element cobalt with other compounds, like derivatives of cyanide and methane (8, 9).

Another name for vitamin B12 is cobalamin. Synthetic vitamin B12 supplements usually have cobalamin in their name.

The most common types of vitamin B12 supplements are (6, 10):

  • cyanocobalamin
  • methylcobalamin
  • hydroxocobalamin
  • adenosylcobalamin

Of these, cyanocobalamin may be considered the most synthetic, as it has a different chemical composition than naturally occurring vitamin B12.

The other three are chemically identical to the vitamin B12 that’s found in foods. Still, when used in supplements, they’re produced in a lab rather than being isolated from natural sources.


There are four forms of vitamin B12 supplements, three of which are chemically identical to vitamin B12 found in foods. The fourth form, cyanocobalamin, has a unique chemical composition and is typically used in supplements.

Your body requires vitamin B12 for important functions, like metabolism, production of blood cells, and brain health. Deficiencies of the nutrient can cause a range of mild to severe side effects.

Vitamin B12 blood levels of 200 picomoles per liter (pmol/L) or below are typically considered low, though diagnosing a true deficiency can be complicated (11, 12).

If you worry you might be deficient, it’s best to consult a healthcare professional.

Vitamin B12 deficiencies can cause symptoms, like (13):

  • skin discolorations
  • irregular heartbeat
  • gait, or abnormal walking motions
  • glossitis, which is swelling of the tongue
  • numbness in the hands and feet
  • acute psychosis
  • dementia-like symptoms
  • irritability
  • infertility

In many cases, it can take years for these types of symptoms to appear.


Vitamin B12 deficiency can take years to develop. Symptoms include irregular heartbeat, psychosis, dementia-like symptoms, irritability, and more.

In severe cases of malabsorption or in people with risk factors for vitamin B12 deficiencies, a liquid supplement could help prevent deficiency and associated symptoms. It may even have a few additional health benefits.

Used to treat anemia

Vitamin B12 is crucial to your body’s production of red blood cells.

When the body is unable to produce as many healthy red blood cells as it needs, which is often the case with a vitamin B12 deficiency, it leads to a condition called anemia (11, 14).

Anemia makes you feel weak and fatigued. Severe cases can even damage the heart and nervous systems.

Oral vitamin B12 supplements are a common and effective way to normalize B12 blood levels and prevent vitamin B12 deficiency anemia (15, 16, 17, 18).

Could boost energy levels in cases of deficiency

It’s commonly claimed that vitamin B12 improves energy levels. In theory, this statement does have some truth behind it.

Vitamin B12 helps your body metabolize food and turn it into energy.

What’s more, vitamin B12 deficiency can cause anemia, which is associated with lower energy levels. So, if you’re deficient in vitamin B12, taking a supplement could help you feel more energetic.

However, if you’re already getting enough of the vitamin from your diet, it’s unlikely that you’ll notice any changes to your energy levels by taking a vitamin B12 supplement.

Might prevent birth defects

Vitamin B12 deficiency can be especially dangerous for those who are pregnant or breastfeeding.

A lack of the vitamin during these phases can cause cognitive and developmental delays, neural tube defects, and low rates of weight gain in infants, also known as failure to thrive (19, 20).

Researchers are still exploring how oral supplements are best used to prevent these side effects. It appears that maintaining adequate blood levels of the vitamin, like through supplementation, does improve birth outcomes (21, 22, 23, 24).


A vitamin B12 deficiency can cause a range of mild to severe side effects, including anemia, weakness and fatigue, and birth defects in infants.

Many brands of liquid vitamin B12 are available in stores and online. They typically come in a small bottle that includes an eyedropper syringe for administration.

Most manufacturers also recommend a specific dosage. Still, it’s best to consult with your doctor first, since nutrient needs vary from person to person and liquid vitamin B12 supplements could interact with other medications or supplements.

It’s worth noting that liquid vitamin B12 supplements often contain other ingredients, like fruit and vegetable extracts, glycerin, sweeteners, and more.

The amount of vitamin B12 included in a supplement varies between brands. This is another reason why it’s important to look closely at the manufacturer’s instructions for the product.

There are no official dosage recommendations for liquid vitamin B12 supplements.

For reference, these are the Recommended Dietary Allowances (RDA) for vitamin B12 by sex and age group — indicating the daily amount needed for healthy individuals (25):

  • Men 14–18: 2.4 mcg
  • Men 19+: 2.4 mcg
  • Women 14–18: 2.4 mcg
  • Women 19+: 2.4 mcg
  • During pregnancy: 2.4 mcg
  • During lactation: 2.8 mcg

The RDA for vitamin B12 for most people is 2.4 mcg per day. Most supplements vary in vitamin B12 content and dosage. Follow the manufacturer’s instructions or ask a healthcare professional for advice.

Liquid vitamin B12 supplements are considered safe for most people.

Because water-soluble vitamins like vitamin B12 are regulated by the kidneys, any excess that your body doesn’t need will be excreted in your urine. This makes it unlikely that you’ll experience adverse side effects from taking too much.

Nevertheless, there have been rare reports of people experiencing severe allergic reactions to vitamin B12 supplements.

These cases were due to allergies to cobalt molecules or other ingredients in the supplements, like benzyl alcohol. An allergic reaction could cause symptoms, including (26, 27):

What’s more, though low vitamin B12 levels can have detrimental effects on newborns, it appears that high levels of the vitamin can as well. One study found that elevated blood levels of vitamin B12 in mothers increased the risk of autism in their newborns (28).

This, again, highlights the importance of working with a healthcare professional to appropriately assess and treat any vitamin B12 abnormalities you’re worried about.


Vitamin B12 supplements are safe and effective for most people, although a few people have experienced allergic reactions.

Liquid vitamin B12 is not the only form of vitamin B12 supplements. Pill capsules and gummies are commonly available oral options.

The best option likely varies from person to person and depends on what it’s being used for.

How bioavailable — or in other words, how absorbable a vitamin is — is often influenced by factors, like age, genetics, and a person’s digestive system (10).

For example, people with conditions affecting the digestive system might not benefit from liquid, gummy, or pill forms of vitamin B12. Instead, a nasal spray or intramuscular injection might be more suitable (18, 29, 30).

Many experts consider intramuscular vitamin B12 injections to be the safest and most effective option. On the downside, they’re more expensive and must be administered under the supervision of a healthcare professional (31, 32).

Still, multiple studies have also found oral vitamin B12 supplements to be safe and effective (33, 34, 35, 36).

Ultimately, consulting a doctor is the safest way to determine which vitamin B12 supplement is best for you.


Intramuscular injections are considered the gold standard when it comes to vitamin B12 supplements. However, both liquid and pill forms of vitamin B12 are safe, effective, and affordable.

To prevent vitamin B12 deficiency, some people choose to take vitamin B12 supplements.

It could help you avoid the adverse side effects that can accompany vitamin B12 deficiencies, like anemia, low energy levels, and complications for infants at birth.

Vitamin B12 supplements, including the liquid form, are safe and effective for most people. Still, there have been reports of allergies or excessive blood levels of the nutrient in some people.

Keep in mind that eating a diet rich in meat, seafood, eggs, dairy, or products fortified with vitamin B12 provides enough of the nutrient for most people.

Work with a trusted healthcare professional to determine the best vitamin B12 supplement regimen for you.

Just one thing

Try this today: Add more vitamin B12 foods to your diet by enjoying beef, seafood, eggs, dairy, and fortified breakfast cereals or nondairy products, like soy milk.

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