Is It Better to Take B12 Injections or Tablets? A Guide to Your Nutritional Needs

October 22, 2025 •

5 min read

An estimated 6% of adults under 60 in the UK and US have a vitamin B12 deficiency, making supplementation a common necessity. When considering treatment, a key question arises: Is it better to take B12 injections or tablets? The best method depends on the root cause and severity of the deficiency, along with individual absorption capabilities.

Quick Summary

This guide compares the efficacy, absorption, cost, and convenience of B12 injections versus tablets. The optimal choice depends on deficiency severity, underlying medical conditions like malabsorption, and personal preference.

Key Points

Absorption Rate: B12 injections offer rapid, near-complete absorption directly into the bloodstream, while oral tablets rely on passive diffusion for absorption.
Speed of Effect: Injections can produce noticeable effects, like increased energy, within days, making them ideal for severe deficiencies. The effects of oral tablets are more gradual and cumulative.
Suitable Candidates: Injections are generally recommended for those with severe deficiencies, pernicious anemia, or gastrointestinal malabsorption issues. Tablets are suitable for mild deficiencies, maintenance, and those who can absorb B12 orally.
Cost and Convenience: Oral tablets are typically much more affordable and convenient for at-home use. Injections are more expensive and require regular clinic visits.
Equivalent Efficacy: Studies confirm that oral B12 can be just as effective as injections for normalizing serum B12 levels over a period of months, especially for maintenance therapy.
Sublingual Advantage: Sublingual (under-the-tongue) tablets may offer slightly more efficient absorption than standard oral tablets, and some studies show them to be highly effective, even rivaling injections in efficacy for increasing serum levels.

Understanding B12 Absorption

To understand whether B12 injections or tablets are better, one must first grasp the basic mechanisms of B12 absorption. The body can absorb vitamin B12 in two main ways: actively and passively.

Active Absorption: This method is the primary way the body absorbs dietary B12. It requires the presence of intrinsic factor, a protein produced in the stomach, which binds to B12 and facilitates its absorption in the small intestine. A deficiency of intrinsic factor, known as pernicious anemia, prevents this process, regardless of dietary intake.
Passive Absorption: With sufficient oral amounts of B12, a small percentage can be absorbed through a process called passive diffusion. This process bypasses the need for intrinsic factor entirely, which is why oral supplementation can be effective for some individuals with malabsorption issues.

B12 Injections: Pros and Cons

B12 injections are a standard treatment for deficiencies, especially for those who cannot absorb the vitamin orally. The most common forms used for injections are hydroxocobalamin and cyanocobalamin.

How Injections Work

Injections are typically administered intramuscularly, directly into a muscle. This method delivers B12 directly into the bloodstream, bypassing the entire digestive system. This ensures nearly complete absorption, leading to rapid increases in blood B12 levels. For individuals with severe deficiencies or certain medical conditions, this can lead to a quick improvement in symptoms like fatigue, sometimes within 24 to 48 hours.

When to Choose Injections

Injections are often the preferred choice for specific groups and conditions:

Pernicious Anemia: Since this autoimmune condition prevents intrinsic factor production, injections are the most effective treatment to bypass the non-functional absorption pathway.
Severe Deficiency: For moderate to severe deficiency, injections provide a faster and more reliable boost to B12 levels, which is crucial for preventing neurological damage.
Malabsorption Issues: Individuals with digestive disorders like Crohn's disease, celiac disease, or those who have undergone gastrointestinal surgery (e.g., gastric bypass) may struggle to absorb oral B12 effectively.
Patient Preference: Some patients may prefer less frequent injections over a daily tablet regimen.

B12 Tablets: The Oral Alternative

For many, oral supplementation is a convenient and effective way to manage B12 levels. Tablets are available over-the-counter and offer a less invasive option.

How Oral Supplements Work

Oral supplements rely on passive diffusion for absorption, especially when higher amounts are used. This can be effective even for many individuals with malabsorption conditions, as adequate amounts can ensure sufficient B12 is absorbed passively. While the absorption rate is lower than with injections, studies have shown that oral B12 can be as effective as injections for normalizing serum B12 levels over several months.

Sublingual vs. Standard Tablets

Oral supplements come in different forms, including standard tablets and sublingual tablets that dissolve under the tongue. Research suggests that sublingual absorption may be slightly more efficient than swallowing, though both methods have shown effectiveness. Some studies have found sublingual supplements to be superior to intramuscular injections for raising blood levels, potentially due to sustained passive absorption over a longer period.

When to Choose Tablets

Oral tablets are a great option for many scenarios:

Mild Deficiency or Prevention: For those with a mild deficiency, or for individuals at risk (like vegans and vegetarians), daily oral supplementation is an easy and effective preventative measure.
Maintenance Therapy: Many people who initially receive injections for a severe deficiency can switch to oral tablets for long-term maintenance.
Convenience and Cost: Oral tablets are generally more convenient and significantly cheaper than injections, especially when considering the costs of clinic visits.
Needle Aversion: For those who dislike injections, a pill or sublingual tablet is a painless alternative.

Injections vs. Tablets: A Comparison Table


Feature	B12 Injections	B12 Tablets
Absorption	Very high, rapid and complete, bypassing the digestive system entirely.	Lower, relies on passive diffusion in the gut.
Speed of Results	Fast, with symptom improvement (e.g., energy boost) often felt within days.	Slower and more gradual, taking weeks to months to normalize levels.
Convenience	Requires a clinic visit for administration, but is less frequent.	Can be taken easily at home, typically requires daily intake for consistent levels.
Cost	Generally more expensive due to the medication and professional administration fees.	Significantly less expensive than injections over the long term.
Target User	Those with severe deficiency, pernicious anemia, or known malabsorption issues.	Individuals with mild deficiency, vegans/vegetarians, or for maintenance after injections.
Side Effects	Rare but possible allergic reactions, temporary injection site soreness.	Uncommon and typically mild, though some may experience minor digestive issues.

Factors Influencing Your Choice

Several factors should be weighed when choosing between injections and tablets. The cause of your deficiency is paramount. If it's a severe absorption issue, like pernicious anemia, injections may be the only effective initial treatment. If it's due to poor dietary intake or a milder issue, oral tablets are likely sufficient. The cost is another significant consideration. The long-term expenses of frequent clinic visits for injections can be substantial, whereas tablets are much cheaper. Additionally, lifestyle preferences play a role; some may prefer the set-it-and-forget-it nature of an injection, while others prefer the daily routine of a pill. Finally, the choice of B12 form matters; methylcobalamin is the bioactive form, while cyanocobalamin is synthetic, but both have shown effectiveness. For a deep dive into the clinical evidence comparing the two methods, the American Academy of Family Physicians offers a review that confirms the equivalent efficacy of high-dose oral B12 and intramuscular injections over time.

Conclusion: Making the Right Decision for You

In conclusion, there is no single answer to whether is it better to take B12 injections or tablets. For those with severe malabsorption, like pernicious anemia, injections offer rapid, reliable, and necessary treatment. However, for most other cases, including mild deficiencies and long-term maintenance, oral tablets, especially sublingual versions, have been proven highly effective and are more convenient and cost-efficient. The most crucial step is to consult a healthcare provider. They can perform a blood test to determine your B12 levels and discuss the underlying cause of any deficiency. Based on your specific medical history and needs, they will help you decide the most appropriate and effective course of treatment. Whether you choose injections or tablets, the goal is the same: to restore and maintain optimal B12 levels for your overall health and well-being.

Frequently Asked Questions

B12 injections are necessary for individuals with pernicious anemia or other severe malabsorption issues that prevent the body from absorbing B12 from the digestive tract, regardless of the amount consumed. They are also used for severe deficiencies to rapidly restore vitamin levels and prevent neurological damage.

Yes, in many cases, oral B12 can be effective for treating pernicious anemia by leveraging passive diffusion, which bypasses the need for intrinsic factor. However, this should only be done under a doctor's supervision.

Injections typically lead to faster results, with improvements in symptoms like fatigue often appearing within days. The effects of oral tablets are more gradual, and it can take several weeks or months of consistent use to notice significant improvement.

Methylcobalamin is the natural, active form of B12, while cyanocobalamin is a synthetic form that the body must convert. While some proponents favor methylcobalamin for its bioavailability, both forms have been shown to be effective at raising B12 levels. Cyanocobalamin is more stable and often more affordable.

B12 injections are generally safe with few side effects. The most common side effects are temporary soreness or redness at the injection site. Rare side effects include mild diarrhea, itching, or, in very rare cases, an allergic reaction.

Some studies suggest that sublingual tablets are highly effective and may be absorbed more efficiently than standard swallowed tablets. This is likely due to direct absorption into the bloodstream through the tissues under the tongue, though both forms work via passive diffusion at sufficient amounts.

Yes, it is always recommended to consult a doctor before starting any B12 supplementation. They can determine if you are truly deficient with a blood test, identify the cause, and help you choose the most appropriate and effective treatment option.

Long-term, oral tablets are significantly cheaper than injections, which involve the cost of the medication and professional administration fees. Studies have shown substantial potential cost savings when converting patients from injections to oral therapy.