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Sublingual vitamin B12: is taking supplements under your tongue more effective?

yael coopermannopell wong

Reviewed by Yael Cooperman, MD, written by Nopell Wong

Last updated: Mar 03, 2021
7 min read


If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.

When scientists develop medications and supplements, they have to take into account that any pill you swallow has a long and treacherous route to travel before reaching your bloodstream. 

Active ingredients have to be packaged so they’re protected from the extreme acid of your stomach, as well as all of the digestive enzymes they meet along the way. Once a medication is absorbed from the digestive tract into your bloodstream it has to pass through the liver, which can break down or significantly alter active ingredients. Every obstacle along the way alters the amount of each active ingredient. 

That’s where sublingual treatments come in. It turns out that the spot under your tongue is sort of like a trap door. When you put a medication under your tongue, it goes straight into the bloodstream, bypassing digestive juices and the liver’s filtration system. It’s a fast and effective method, but you shouldn’t be taking all your pills sublingually—here’s why.


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Can all supplements be taken sublingually? 

Drugs are designed a specific way for a reason. So placing a pill that’s designed to be swallowed under your tongue instead can be dangerous and even deadly. Also, sometimes drug researchers take advantage of these obstacles and create inactive ingredients that need to go through your liver in order to be activated. That’s why you should always take medications as directed. 

When it comes to vitamin B12, your body needs this essential vitamin to build red blood cells, get energy out of the food you eat, support your nervous system, and more. Since our bodies can’t produce B12 on their own, we have to get it from our food (like meat and dairy products), but not everyone gets enough. Manufacturers have created products like breakfast cereals and non-dairy milk fortified with B12 to tackle this problem, but many people still have a B12 deficiency. 

If your healthcare provider diagnoses you with a B12 deficiency, they may recommend that you start taking a supplement, which is available in pill form that needs to be swallowed as well as in a sublingual form you just pop under your tongue. If you have a severe deficiency, they may offer you a vitamin B12 injection. 

For people with low levels of this important vitamin, supplements are often a first choice. Vitamin B12 comes in many forms, however, sublingual B12 (taken under the tongue) is one option (NIH, 2020). 

If you’re looking to take vitamin B12 supplements and are considering the sublingual route, here’s what you need to know.

Is sublingual vitamin B12 more effective than other forms of the vitamin?

Well, while the sublingual route would seem to be more effective in theory, research doesn’t actually back it up. Compared to other types of vitamin B12 supplements, the sublingual method doesn’t seem to be any more or less effective. 

A study from 2006 didn’t find any difference in effectiveness between sublingual and oral vitamin B12 supplements (Yazaki, 2006). Another study concluded that the sublingual and oral method were equally effective in resolving B12 deficiency in participants (Sharabi, 2003). 

Comparing the sublingual method to vitamin B12 injections, research found that taking B12 under the tongue had a higher absorption rate, making it a better option (Bensky, 2019). 

Taking vitamin B12 sublingually may also be a good option for people with a condition called pernicious anemia. This condition is characterized by a lack of intrinsic factor, a protein that plays a crucial role in helping the body absorb vitamin B12 (Ankar, 2020). 

Intrinsic factor is produced by the cells that line your stomach, and is one of the main components that drives your B12 intake capacity. People with pernicious anemia, may benefit from sublingual B12 as they lack intrinsic factor and have a lot of trouble absorbing B12 through their digestive system (Ankar, 2020). 

Why do you need  B12 supplements?

Vitamin B12, also known as cobalamin, is a molecule that isn’t easily absorbed into our systems. 

Research has shown that even in people without any underlying health conditions, when taking a 500 microgram oral supplement, only 10 micrograms (or 2%) is absorbed (Carmel, 2008). Improving absorption rates is a good way to make sure you get what you need. 

Sublingual supplements come tablets or liquid drops. If you’re trying the liquid method, you put drops under your tongue instead of ingesting them like you would an oral supplement. The thought behind administering it under the tongue is that it can be absorbed directly into the bloodstream through what’s called the mucous membrane in your mouth (UMichigan Health Library, 2018). This method is thought to enhance absorption, but research doesn’t fully confirm this. 

Nonetheless, sublingual B12 is a viable way to supplement B12 levels for people deficient in the vitamin. This method may also be useful for children or individuals who have trouble swallowing pills. 

How to use sublingual B12 supplements

If you’re a first time sublingual B12 user (that’s a mouthful), here’s what you should know.

Sublingual B12 supplements come in two forms: tablets and liquid drops. Whichever you decide on, the idea is to place the correct amount under your tongue and let it dissolve completely—without swallowing (UMichigan Health Library, 2018). 

Sublingual tablets come in 500 or 1000 mcg dosages. The recommended daily intake of B12 is between 2.4 and 2.8 mcg, but its low absorption rate is the reason for such high dosages in supplements (NIH, 2020). 

Do vitamin B12 supplements have side effects?

Vitamin B12 supplements are generally considered safe. Those with severe deficiencies may require higher doses of vitamin B12, which can cause side effects including dizziness, headache, anxiety, nausea, and vomiting (Al Amin, 2021). If you’re unsure what dosage you need, a healthcare professional can help determine the appropriate amount. 

Symptoms of a vitamin B12 deficiency

Not getting enough vitamin B12 can cause some unpleasant symptoms. Common signs of B12 deficiency include fatigue, weakness, constipation, loss of appetite, and weight loss (NIH, 2020).

A B12 deficiency is more common in older adults, with past surveys showing that roughly 6% of people 60 years and older aren’t getting enough vitamin B12. The prevalence of this deficiency also increases with age (Allen, 2009). 

Because B12 is critical for proper nervous system function, a deficiency can lead to neurological symptoms, such as confusion, poor memory, depression, and difficulty maintaining balance (Serin, 2019). These symptoms can also be caused by other health conditions or vitamin deficiencies, therefore it’s important to see a healthcare professional and get properly diagnosed. 

Who is most at risk of a B12 deficiency?

Some individuals are more prone to a B12 deficiency than others. People at risk of a vitamin B12 deficiency usually have conditions that hinder the absorption of B12 from their gastrointestinal system. 

Here are some of the groups who may be more at risk for a B12 deficiency (NIH, 2020):

  • Those with atrophic gastritis: Between 10 and 30% of older adults are afflicted with atrophic gastritis, which results in decreased absorption of foods containing B12. 
  • People with pernicious anemia: Individuals with pernicious anemia may also be at risk for B12 deficiency. Individuals with this condition lack the intrinsic factor we mentioned earlier, which is one of the key proteins responsible for B12 absorption (O’Leary, 2010). 
  • Individuals with gastrointestinal issues: People living with disorders of the stomach or small intestine may have a more difficult time absorbing vitamin B12 from their food. In addition, patients who’ve undergone gastrointestinal-related surgeries may be at risk of B12 deficiency due to malabsorption.  
  • Vegetarians and vegans: Since most foods that contain B12 naturally are animal products like meat, eggs and dairy, vegetarians and vegans are at greater risk of developing a B12 deficiency. 

Other sources of vitamin B12

Sublingual vitamin B12 is not the only solution if you’re lacking in the B12 department. Below are some of the main ways you can get more vitamin B12 in your system: 

  • Diet: Animal products like poultry, meat, fish, eggs, and milk contain vitamin B12. Foods, such as cooked clams and beef, provide well over the recommended daily intake of B12. Trout, salmon, tuna, and fortified yeast also give you just the right amount. Vitamin B12 is not typically found in plants, so vegans and vegetarians may need to look for fortified breakfast cereals that include B12 or opt for a regular supplement (NIH, 2020). 
  • Oral supplements: Cyanocobalamin and methylcobalamin are popular types of B12 supplements. Cyanocobalamin is the synthetic version of B12, and methylcobalamin is the natural form (Al Almin, 2021). Both come in the form of oral tablets, capsules, and gummies, which are available at most drugstores.
  • B12 injections: Intramuscular injections of vitamin B12 is one of the most common forms of administration, but it must be done by a medical professional (Shipton, 2015). Intranasal treatment (via a nasal spray) of B12 is also available through a prescription (Andrès, 2018). 

If you think you might be suffering from B12 deficiency, consult with your doctor to discuss what avenues of treatment are available for you to pursue. Rest assured that there are plenty of solutions out there to resolve B12 deficiency, whether it’s through sublingual/oral tablets, diet, or injections. 


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Yael Cooperman is a physician and works as a Senior Manager, Medical Content & Education at Ro.