Should You Use Sublingual B12 Over Capsules & Shots?

Should You Use Sublingual B12 Over Capsules & Shots?

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Up to 40-50% of the population in the US is deficient in vitamin B12. 

That number gets even worse if you have hypothyroidism (up to 50% of these patients have B12 deficiency). 

It gets even more important when you realize that vitamin B12 is vital for cellular energy production and detoxification systems via the glutathione pathway (1).

​What you may not realize is that many simple over-the-counter medications may be blocking your ability to absorb vitamin B12. 

I’m talking about acid blockers, H2 blockers, and even non-steroidal anti-inflammatory medications. 

Because of this, it is very important to understand if you are deficient and to replace your levels if you are. 

There are some nuances to replacement that make sublingual B12 ​and vitamin B12 shots superior to other forms of B12 which we will talk about below: 

Symptoms of Vitamin B12 Deficiency

​We are going to talk about how to properly test for and evaluate your B12 levels but there are a few things you should know:

1. ​Serum vitamin B12 levels aren’t the best marker for assessing your CELLULAR B12 level

2. Standard ranges fail to identify patients with subclinical vitamin B12 deficiency (which means many patients may not have full-blown symptoms of vitamin B12 deficiency but they do experience some)

3. Absorption issues from hormone imbalances are not widely appreciated (particularly hypothyroidism)

4. Methylation issues are very common (up to 40% of patients) and many patients unknowingly supplement with cyanocobalamin which may increase serum levels but will not improve symptoms

​5. Oral preparations of Vitamin B12 may increase serum levels but many patients remain symptomatic until they use sublingual or vitamin B12 injections due to low cellular concentrations

6. Proton pump inhibitors (acid blockers) and over-the-counter non-steroidal anti-inflammatory agents can change the environment of the GI tract predisposing to nutrient deficiencies

Unfortunately, that isn’t an exhaustive list, but it does give you a pretty good idea of why you should be concerned about your vitamin B12 levels. 

The chances are high that you fit into one or more of the categories listed above.

And if you do you should take a look at the symptoms of Vitamin B12 deficiency so you know if supplementing is a good idea or not.

Common symptoms of vitamin B12 deficiency:

  • Fatigue and a subjective feeling of “low energy levels”
  • Hair loss and changes in skin color (usually manifests as pale skin)
  • Brain and cognitive issues like decreased memory, depressive-like symptoms, mood changes, and “brain fog”
  • Shortness of breath or difficulty with sustained exercise
  • Megaloblastic anemia
  • Depression and even a dementia-like syndrome can be confused with Alzheimer’s
  • Nerve conditions like nerve pain and peripheral neuropathy

Why are the symptoms so diverse? Because vitamin B12 has action at the cellular level and is in charge of multiple pathways where a deficiency may lead to the subjective feeling of “fatigue” or “low energy”.

If you are experiencing any of these symptoms without a clear reason then checking your vitamin B12 levels would be the next appropriate step: 

​How to check for Vitamin B12 Levels

It’s important to realize that some medical conditions are not appreciated and not taken as seriously as others.

In the conventional medical world, most vitamin deficiencies are taken as less serious than other medical conditions due to a variety of reasons (we won’t talk about that today), despite the fact that replacing these nutrients can significantly improve symptoms in many patients.

Because of this, it’s important for you to have a basic understanding of how to assess your vitamin B12 levels and how to understand if you are “sub-optimal” and not just in the “normal range”.

If you have “sub-optimal levels” with symptoms, it’s worth a trial of B12 even if your serum B12 levels are normal.

Vitamin B12 is a water-soluble vitamin which means any excess will be urinated out of your body (assuming you have normal kidney function), so the risk of overdose is basically non-existent. ​

Having said that let’s talk about the best tests to order to identify vitamin B12 deficiency. 

Check these labs to correctly identify Vitamin B12 deficiency:

  • Serum B12 levels: You should be > 900 (normal levels typically fall between 300-900). Levels in the 400-500 range usually indicate a deficiency, especially if coupled with the symptoms above. 
  • Serum homocysteine levels: Your level should be < 9.0. High homocysteine levels may indicate issues with the activation of B12 at the cellular level (2). Patients with methylation issues may present with “normal” serum levels of B12 but with very high homocysteine levels. 
  • Mean corpuscular volume (MCV): Your MCV should be less than 92 but greater than 80. This test is part of the CBC (which almost every Doctor will order) and tells you how large your red blood cells are (3). A high MCV is very sensitive to B12 and folic acid deficiency. Beware that iron deficiency can artificially lower your MCV value and mask vitamin B12 deficiency. 

The combination of these lab tests plus your symptoms can really shed light on your cellular vitamin B12 status. 

I consider homocysteine and MCV levels to be more accurate at assessing cellular concentrations of vitamin B12 than serum B12 levels in most cases.

Another important note is that the values that I suggested above represent the “optimal” values.

They may not necessarily flag as abnormal because your results may fall within the standard “normal” range but that doesn’t mean you are really normal.

Why I use Vitamin B12 in Almost Every Patient

​I find that many patients are not only vitamin B12 deficient but they also have issues with the cellular activation of Vitamin B12. 

Because I also focus on hormone imbalances I find MANY hypothyroid patients to also be both vitamin B12 deficient and iron deficient.

​I’ve been able to see the benefits of proper B12 replacement firsthand so I understand how critical low levels can be. 

With that said let me go over some of the benefits you can potentially receive by replacing your levels (if you are deficient): ​

  • Improved and sustained energy levels throughout the day (some patients don’t appreciate the energy levels until they stop taking their B12)
  • Improvement in sleep (increased depth and feeling “renewed” when waking)
  • Improved mental clarity and cognition
  • Ability to exercise longer and harder
  • General improvement to skin, hair, and nails (helpful if your hair loss is due in part to vitamin B12 but iron generally plays a larger role in hair loss)
  • Reduced nerve pain and muscle aches/tension

These beneficial side effects are not necessarily seen in every patient because not every patient presents with the same symptoms. 

Generally patients with B12 deficiency present with very non-specific symptoms like small changes in mood or a general feeling of fatigue.

Occasionally some patients don’t realize how bad they were feeling until they feel better, and you may be in that position as well. ​

Sublingual B12 vs B12 shots and injections

​I’ve written extensively about the difference between vitamin B12 shots in the past. 

Please read this post for a very in-depth post on why I believe vitamin B12 shots to be superior to oral forms of vitamin B12.

​Having said that I still believe there are reasons you would want to use sublingual vitamin B12: 

  • Inability to tolerate shots (or fear of needles)
  • To boost levels in between Vitamin B12 injections (generally shots are taken once per week) so some patients will use daily sublingual B12 in addition to weekly shots of B12
  • Allergies to fillers or dyes in tablet/pill/shot forms of Vitamin B12
  • Inability to find B12 shots

​My recommendation for B12 shots comes from using both oral forms and injection forms extensively on patients with multiple and chronic medical conditions. 

Overall I’ve found a much greater response to Vitamin B12 injections over even sublingual B12.

I have also seen patients who have taken sublingual B12 daily without symptomatic relief and then respond to vitamin B12 shots in a very short time.

I still think sublingual B12 formulations have value, but whenever possible my recommendation is to take an injection or shot form. 

How to Supplement with Vitamin B12

How to tell if you Need it

If possible it’s ideal to check your serum B12 levels prior to supplement but it is not necessary.

Unfortunately, most standard B12 tests, including serum B12, do not adequately tell you how much B12 is in your cells.

They can give you an idea of serum B12 but that doesn’t always correlate with cellular B12 levels which is what we care about.

In addition, B12 supplements are incredibly safe and unlikely to cause any issues unless you have kidney problems.

Having said that, it’s still a good idea to get a baseline B12 level (or use a combination of other testing markers) so you can compare your results after supplementing.

If you do opt for testing first, here are some tests you can consider getting:

  • Serum B12 – Should be > 1,000
  • Homocysteine levels – Should be < 9
  • MCV – Should be < 92
vitamin b12 lab test results form a patient with a normal serum vitamin b12 level but who may still benefit from vitamin b12 supplementation.

How to Use

  • 1,000-5,000 mcg per day preferably taken in sublingual form
  • If you are severely deficient in Vitamin B12 you may need to use methylcobalamin injections once per week
  • In terms of effectiveness, B12 shots are the most effective while both oral and sublingual forms tend to be about equal.


I’ve compiled a list of frequently asked questions that many patients have asked me over the years. 

If you still have questions about the type of B12 to use, the dosage necessary, when/how you should use it, etc. Please refer to the FAQ below.

What is the difference between Methylcobalamin and Cyanocobalamin?

Cobalamin is the term used for the vitamin B12 and the Cyano or Methyl portion refers to what the B12 is bound to.

Methylcobalamin is felt to be superior to cyanocobalamin because it does not require methylation for activation in the body.

That means that methylcobalamin is easier on the body in terms of cellular use.

If you are taking cyanocobalamin and have not noticed an improvement in your symptoms it could be that you are using the wrong form of vitamin B12.

If you have a methylation issue then you will want to use methylcobalamin.

What is the best B12 Dosage: 1,000mcg or 5,000 mcg?

You will have to figure out what your body does best on, but in general, I recommend using 5,000mcg per day in sublingual form as long as you are not extremely sensitive to supplements and/or medications.

If you are sensitive, or you experience fatigue as opposed to an increase in energy when taking vitamin B12 then using a smaller dose less frequently will likely be better for your body. ​

​What is sublingual vitamin B12 used for?

Sublingual Vitamin B12 is used because it is felt to have superior absorption over oral tablets that are absorbed in the GI tract.

This is especially important for patients who have any GI-related problems: reflux/heartburn, SIBO/SIFO, chronic constipation, leaky gut, patients who are on acid blockers, etc.

These patients will have a difficult time absorbing B12 unless they have appropriate amounts of stomach acid and HCL. ​

Does Sublingual B12 help with Weight Loss?

By itself, B12 will generally NOT help with weight loss.

It may, however, improve energy levels (assuming you are deficient) which may allow you to increase your activity and help balance hormones leading to weight loss.

Any benefit of sublingual vitamin B12 as it related to weight loss is most likely due to some other component.

The addition of MIC (methionine, inositol, and choline) to methylcobalamin in fat burner shots is felt to increase triglyceride mobilization and may improve weight loss, but these are only found in the injection and shot form. 

What is sublingual methyl B12?

Sublingual Methyl B12 refers to Vitamin B12 in the methylcobalamin form. It is felt to be superior to cyanocobalamin and the methyl form is better and easier to absorb.

Does Sublingual B12 have any side effects?

Generally, vitamin B12 is very well tolerated.

Any excess vitamin B12 in the serum will be urinated out of the body in the presence of functioning kidneys.

We are really only concerned about toxicity from fat-soluble vitamins (A, D, E, and K). 

Having said that some patients do get a paradoxical response to B12 and present with fatigue, headaches, and flu-like symptoms.

This is felt to be due to the detoxification effect of B12 in patients who have methylation issues.

The increase in the production of glutathione and other detoxification enzymes may result in the liberation of these from the body resulting in symptoms.

I’ve found that patients who experience these side effects simply reduce the dosing and frequency of their B12 the symptoms usually resolve. ​

What does sublingual mean?

Sublingual refers to absorption under the tongue.

Certain medications (nitroglycerin) and supplements can be absorbed and utilized by the body via this absorption route.

Not all medications and nutrients are small enough to get absorbed or need breakdown via gastric enzymes for activation for the sublingual route, but whenever possible there is a benefit to using this route as it bypasses potential damage/absorption issues in the GI tract. ​

When and how should I use B12?

Vitamin B12 is best when used in the morning (away from thyroid medication if you are using it). 

Some patients find B12 to be very stimulating, if you fall into this category it’s best to use it early in the day as opposed to in the evening. 

On rare occasions some patients do find that B12 improves their sleep – if you fall into this category then using B12 at night may be better for you.

Recap & Final Thoughts

Vitamin B12 deficiency is very common and easily misdiagnosed. 

Because of this, I recommend any patient who is symptomatic and has suboptimal levels of vitamin B12 (as defined above) consider a trial of sublingual B12. 

Sublingual B12 has superior absorption over other oral preparations of B12 and is generally well tolerated. 

If you are supplementing with B12 make sure to use Methylcobalamin and not Cyanocobalamin. 

If you still don’t have an improvement in your symptoms on sublingual B12 then consider using methylcobalamin injections.

Now it’s your turn:

Are you using sublingual B12? Does it help with your symptoms?

Why or why not?

Leave a comment below! ​




b12 shots vs sublingual b12 which is best

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About Dr. Westin Childs

Hey! I'm Westin Childs D.O. (former Osteopathic Physician). I don't practice medicine anymore and instead specialize in helping people like YOU who have thyroid problems, hormone imbalances, and weight loss resistance. I love to write and share what I've learned over the years. I also happen to formulate the best supplements on the market (well, at least in my opinion!) and I'm proud to say that over 80,000+ people have used them over the last 7 years. You can read more about my own personal health journey and why I am so passionate about what I do.

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8 thoughts on “Should You Use Sublingual B12 Over Capsules & Shots?”

  1. I have awful spasms in my body for years no help from the medical community. Recently landed in the ER for check tightness and was given nitrogylcerin which aleviated it but they said my heart was fine no cardiac event happened. When in the er I told the PA about my spasms she tested my B-12 it was 317 reference range is 300-2000pg/ml. She said it was fine. However, if I am reading this article correctly it is stating that my B-12 is sub optimal and not in a good range. That it should be >1000 is that correct? I also had my iron tested it said my ferratin was a 5 with a reference range of 30-202 ng/mL which is low. I was told I have mild anemia. I have heavy periods every 3 weeks. I have non alcoholic fatty liver disease from taking nsaids over the years and my type 2 diabetes which is now undercontrol through a very restrictive diet(a1c went from 6.7 to 5.1). I was reading on the web that b-12 is stored in the liver. Will this be a problem? And I was wondering how much I should take of the b-12? I was thinking starting off with 1250? I purchased the liquid form and the kind you mentioned. I also purchased liquid ferrum as well.

  2. Thanks for your post… I’ve been using B12 methylcal tablets sublingual (1000 mcg daily) for 2 months. I was having vertigo and searched the internet and utube for causes and remedies, which is how I learned about B12 sublingual tablets. After I started taking the B12, the vertigo began to slowly decrease and finally, 6 weeks after the vertigo began, it ended. I also noticed that my toenails improved as did the skin on my face. Also, and this is weird, my left index finger and nail, which had been yellow for about 1 yr, is now normal in color.

    I’m 64, female, taking 88 mcg of Levothyroxine daily.

  3. I have been diagnosed with Pernicious anemia, and have been receiving 1000 mcg shots monthly, for the last 2 years. My condition is better than what it was before the shots, but not what I would consider normal. My GP test my levels one week after my last shot and my reading was 650. He told me that this means the shots are working; but I still am symptomatic, but he will not increase my dosage. Would sublingual B12 be beneficial for someone with Pernicious Anemia, such as myself? If so, what dosage?

    • Hi Endel,

      Most doctors are clueless about vitamins. There is absolutely no risk of overdose using B12 because it is water-soluble. I recommend using 5,000 mcg per WEEK of methylated B12 for the best results. Sublingual may help in your case but injections would likely be better.

  4. Didn’t see your recommendations for B12 – just kicked over to a standard Amazon inventory of B12?!?!?
    Aren’t there any made w/o Stevia and other artificial sugars?

    • Hi Dorthe,

      You should be able to find one that fits your criteria 🙂 Just be sure to get one that has methylcobalamin with the fewest inactive ingredients. The source of the B12 is what matters most.

  5. Excellent article – thanks so much. It was informative, to the point and very helpful. Appreciate the link to good brand. Too many contracting “best of B12” lists. So I am going to order because my doc is on same page as you, but he did not offer injection. B12 Assay test I was 289 ng/l and the range is 180-914. So it looks like I am in range, but my doc said to take 1000 sublingual a day regardless. That said, 289 is low right? Should I ask for a shot? Or should I start with 5000 first – you said there is no thing as too much .. or just start with 1000? Just wondering, you seem very informed in this matter and fatigue/sleep are my issues.

    • Hi Sharon,

      I’m a big fan of injections so my preference would be to start there. You could probably get away with the sublingual form, though. According to my recommended optimal values, yes, a 289 would be considered sub-optimal.


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