Can vitamins be absorbed under the tongue? Unpacking the science of sublingual delivery

January 2, 2026 •

4 min read

Studies have shown that sublingual administration can lead to faster and more efficient absorption for certain nutrients compared to traditional oral pills. This has sparked a popular question: can vitamins be absorbed under the tongue effectively, and what's the science behind this alternative delivery method?

Quick Summary

Many vitamins can be effectively absorbed sublingually by bypassing the digestive system and entering the bloodstream directly. This method offers faster absorption and potentially higher bioavailability for specific nutrients, especially for individuals with compromised digestive function.

Key Points

Sublingual Bypasses Digestion: Placing supplements under the tongue allows nutrients to be absorbed directly into the bloodstream through the oral mucosa, bypassing the digestive system and liver.
Faster Absorption: For some vitamins, sublingual delivery offers a quicker onset of effects compared to oral pills, as it avoids the delays of gastrointestinal processing.
Beneficial for Certain Conditions: People with digestive issues, low stomach acid, or difficulty swallowing often benefit significantly from sublingual supplementation, particularly for vitamin B12.
Not for All Vitamins: The effectiveness of sublingual absorption varies by nutrient; factors like molecular size, lipid solubility, and pH determine how well a vitamin can be absorbed this way.
Proper Technique is Crucial: To maximize sublingual absorption, supplements must be held under the tongue until fully dissolved without eating, drinking, or swallowing.
Formulation Matters: The format of the sublingual product, such as a dissolving tablet or liquid spray, is key to its effectiveness, as is its purity and lack of unnecessary additives.

The Mechanism of Sublingual Absorption

Sublingual administration, meaning “under the tongue,” involves placing a substance in the floor of the mouth where it dissolves and is absorbed by the surrounding mucous membranes. The area under the tongue and cheeks is rich with tiny blood vessels called capillaries.

When a supplement is placed here, it can enter the bloodstream directly, bypassing the gastrointestinal tract and the liver's first-pass metabolism. This process is different from swallowing a pill, which must first survive exposure to stomach acids and digestive enzymes before being absorbed through the intestines.

Factors Influencing Sublingual Efficacy

The effectiveness of sublingual absorption for any given vitamin depends on several key factors related to the substance itself and how it is formulated:

Solubility and Permeability: The vitamin must be soluble in saliva and have a balance of hydrophilic (water-loving) and lipophilic (fat-loving) properties to effectively cross the mucosal membrane via passive diffusion.
Molecular Size: Smaller molecules are more easily absorbed through the mucosa.
pH of Saliva: Saliva's pH level can affect the ionization of the vitamin, which in turn impacts its absorption.
Formulation: The form of the supplement (e.g., liquid drops, spray, dissolving tablet) and the presence of additives can affect how well and how quickly it is absorbed.

Vitamins Best Suited for Sublingual Delivery

While not all vitamins are effective in sublingual form, certain nutrients are well-known to benefit from this delivery method. This is particularly advantageous for individuals with malabsorption issues, compromised stomach acid production, or difficulty swallowing.

Vitamin B12

Vitamin B12 is one of the most common and well-researched sublingual supplements. For absorption through the digestive tract, B12 requires a protein called intrinsic factor, which some people lack due to conditions like pernicious anemia or low stomach acid. Sublingual B12 bypasses this intrinsic factor pathway, allowing for efficient absorption directly into the bloodstream. Some studies even suggest sublingual B12 can be as effective as injections for correcting a deficiency.

Vitamin D

Some evidence supports the effectiveness of sublingual vitamin D, especially in liquid or spray form. One case study showed that a patient with poor oral vitamin D absorption successfully raised their vitamin D levels with sublingual drops. This route bypasses potential issues related to fat absorption in the gut that can affect the uptake of this fat-soluble vitamin.

Oral vs. Sublingual: A Comparison


Feature	Oral Supplements (Pills/Capsules)	Sublingual Supplements (Drops/Tablets)
Absorption Route	Must pass through the digestive tract and liver.	Absorbed directly into the bloodstream through the oral mucosa.
Speed of Action	Slower, as it relies on digestion and can be affected by stomach contents.	Faster for some nutrients, offering quicker onset of effects.
Bioavailability	Can be compromised by stomach acid, digestive enzymes, and liver metabolism.	Avoids first-pass liver metabolism, potentially leading to higher bioavailability.
Ease of Use	Requires swallowing, which can be difficult for some people.	Convenient for those with swallowing difficulties or nausea.
Nutrient Suitability	Works for a wider range of nutrients, including those not well-absorbed sublingually.	Depends on the specific vitamin's properties (e.g., molecular size, solubility).
Formulation	Often contains coatings or additives to protect from stomach acid.	Typically contains fewer additives or fillers.

Practical Considerations for Sublingual Supplementation

If you choose to use sublingual vitamins, proper technique is essential to maximize absorption. You must hold the supplement under your tongue for a few minutes until it is fully dissolved. To enhance effectiveness:

Avoid eating or drinking: Do not eat, drink, or smoke immediately before or during the process, as this can affect absorption.
Stay upright: Remain in a seated, upright position to prevent accidental swallowing.
Allow full dissolution: Let the tablet or drops dissolve completely under the tongue before swallowing any remaining saliva.
Check for taste or irritation: Be aware that some sublingual supplements may have a slightly bitter or sour taste, and can irritate mouth sores.

The Verdict: Can Vitamins Be Absorbed Under the Tongue?

Yes, some vitamins can be absorbed under the tongue, and for certain individuals or specific nutrients like B12, this method can offer benefits. The sublingual route bypasses the digestive system, which can result in faster absorption and higher bioavailability by avoiding the degradation effects of stomach acid and the liver's first-pass metabolism.

However, this is not a one-size-fits-all solution. The effectiveness depends heavily on the specific vitamin's properties and its formulation. While sublingual B12 is a well-established and beneficial option, especially for those with compromised absorption, the advantage for other vitamins like B complex or Vitamin D can be less pronounced or debated. Traditional oral supplements remain a reliable and effective choice for many people. Ultimately, the best method depends on your individual health needs and preferences.

It's always recommended to discuss your supplement routine with a healthcare provider to determine the most suitable delivery method for you. You can find more information on dietary supplement research on the NIH Office of Dietary Supplements website.

Frequently Asked Questions

Sublingual vitamins are absorbed directly into the bloodstream through the vast network of capillaries located in the mucous membrane under the tongue, bypassing the gastrointestinal tract and liver.

Yes, for certain nutrients, sublingual absorption can be much faster. Because the substance enters the bloodstream directly, it avoids the slower process of digestion and metabolism that oral pills undergo.

Vitamins B12 and D are two of the most commonly and effectively absorbed sublingual vitamins. B12 absorption via this route is especially beneficial for people with digestive issues affecting its traditional uptake.

Sublingual supplements are particularly useful for individuals with difficulty swallowing pills, those who experience digestive problems, and older adults, who may have lower stomach acid and intrinsic factor production.

Place the supplement under your tongue and hold it there until it has completely dissolved. Avoid eating, drinking, or smoking during this time to ensure maximum absorption.

No, not all vitamins are suited for this delivery method. The molecular size, solubility, and other properties of the nutrient are critical for effective sublingual absorption. Always follow the manufacturer's instructions.

Potential downsides include an unpleasant taste, minor mouth irritation, and the inconvenience of holding the supplement in place for a prolonged period. The cost can also sometimes be higher than traditional pills.

Research has shown that sublingual B12 can be equally effective as oral high-dose B12 supplementation, and for those with intrinsic factor deficiency, it is often a superior route for correcting low levels.