Is Vitamin B12 Dosage 5000 mcg Safe?
By Scott Burgett | 5.9.18 [updated 3.9.19]
This post may contain affiliate links. Please read my disclosure for more information.
Vitamin B12 supplementation has exploded recently due to the popularity of plant-based diets. Since this vitamin is hard to get strictly through plant foods, medical professionals everywhere recommend supplementing Vitamin B12 for those who follow a vegan, vegetarian, or plant-based diet.
With single serving doses on supplement bottles ranging greatly, it’s confusing to know how much to take on a daily or weekly basis. Additionally, ingesting high quantities of a supplement could have negative health consequences.
Is Vitamin B12 dosage 5000 mcg safe? (mcg = micrograms)
This post will answer that question and explore the risks, benefits, origins, dosing guidelines, and the best supplement recommendations for Vitamin B12.
What is Vitamin B12?
Vitamin B12 is a water-soluble vitamin that plays several pivotal roles in the human body. These functions include red blood cell formation, nerve cell repair, and DNA synthesis.
Each of these processes are vitally important to maintaining health throughout your life.
This fundamental vitamin actually originates from microorganisms that blanket the earth. Once upon a time when modern agriculture was unheard of, these organisms thrived in our soils and mountain streams.
However, since harmful pesticides and power washing are now regular occurrences, these organisms are rarely found in our food supply anymore.
In the scientific community, Vitamin B12 is referred to as a cobalamin.
It gets this name because it’s the only known vitamin that has the form of the metal “cobalt” and still reacts with humans, plants, and animals. Cobalt is actually what gives Vitamin B12 its natural red color.
Now that you understand the role of Vitamin B12, there are two forms forms of the vitamin that are found in fortified foods and supplements.
The Two Forms of Vitamin B12 You Need to Know
Vitamin B12 is the largest and most complex vitamin we know today. In supplements, it comes in two primary forms: methylcobalamin or cyanocobalamin.
These two forms differ in a couple of key areas explained below.
Methylcobalamin is the best absorbed form of supplemental B12 in the body because it is bioactive. In other words, it’s readily available to positively interact with our cells.
This form has a chemical structure that has a methyl group, which consists of a hydrogen and oxygen molecule. This methyl group makes it the most active form of Vitamin B12 in the body.
Methylcobalamin is also the most common form of B12 found in animal foods, which is why meat eaters don’t need to supplement.
The only synthetic form of Vitamin B12, cyanocobalamin differs greatly than other forms because its chemical structure contains cyanide.
This cyanide group is the same as the poisonous cyanide you’ve heard of before, but irrelevant to the body at the levels found in Vitamin B12. It is also the only form of Vitamin B12 that gets created in a lab setting.
The synthetic nature of this form requires more steps in the breakdown of Vitamin B12 and could potentially cause absorption issues.
Cyanocobalamin is used in supplements for years due to its proposed effectiveness. Although more recently, criticisms in the scientific community have started to surface about its:
- Toxic build up in the cells
- Bioavailability due to its complex breakdown process (how effectively it absorbs into your cells)
- Absorption to excretion ratio (what stays and what leaves the body)
Due to these criticisms and recent research, cyanocobalamin is now an inferior form of supplementation to methylcobalamin.
How Does Your Body Process Vitamin B12?
The most prominent source of Vitamin B12 is found in animals products.
Animals get the B12 in two ways: eating grass that has B12 in the soil or through supplementation in their feed. The latter being the most common practice in our world today.
Since humans still eat animals, they get Vitamin B12 through their food. For example, when a person eats meat, the Vitamin B12 in that animal’s tissue enters the stomach.
This B12 is protein-bound, meaning it attaches itself to a protein molecule for transport. Before it enters the small intestine, it has to detach in the stomach.
Once the B12 detaches from the protein in the stomach, it’s picked up by a different protein molecule called intrinsic factor (IF).
IF then enters the small intestine bound to Vitamin B12 and gets separated once again into a group called corrinoids (a class of cobalamins, aka Vitamin B12).
These separated corrinoids attach one more time to a different form of IF and heads to its destination in the small intestine.
Once there, the receptors in the small intestine give the corrinoids (Vitamin B12) first priority to absorb. This ensures the body gets this crucial vitamin over other nutrients that have passed through at the same time.
The supplemental form of B12 gets absorbed much easier through supplements than food. That’s because it’s not bound to protein like in animal tissue.
In fact, the only step it takes to break down is either by chewing or by stomach acid (if swallowed whole). Vitamin B12 is then absorbed directly into the bloodstream and shuttled to its final destination: blood cells, the brain, or DNA.
This makes the supplemental form of Vitamin B12 the most reliable form we have available.
Symptoms of a Vitamin B12 Deficiency
It is non-negotiable for anyone following a vegan or plant-based diet (and in most cases a vegetarian diet) to not supplement with Vitamin B12.
Symptoms of B12 deficiencies often do not show for several years, which is why it’s important to start forming the habit early. The below symptoms are some of the most common from a B12 deficiency.
Early signs of a Vitamin B12 deficiency:
- Unusual fatigue
- Loss of appetite
- Deficient digestion
- Numbness/tingling in hands or feet
- Loss of menstruation
- Unusual behavior changes
- Sore tongue
Late signs of a Vitamin B12 deficiency:
Note that you can still become deficient even though none of these symptoms are detectable. Getting regular blood tests will you get ahead of a potential deficiency, but regular supplementation is the best practice.
Two Vitamin B12 Deficiency Case Studies
A frightening case in the US made it into the Medical Journal of Nutrition in 2007. The journal article was title “Irreversible subacute sclerotic combined degeneration of the spinal cord in a vegan subject.”
This case involved 57-year old man never being able to walk again because he did not supplement with Vitamin B12 on a vegan diet.
Doctors immediately started giving him B12 injections for treatment. This dramatically improved his health, however, his rotten spinal cord left irreversible damage, leaving him paralyzed for the rest of his life.
Deficiencies can even happen to infants with vegan or vegetarian mothers who neglect to supplement with B12 during pregnancy.
In 2014, a Chilean 12-month old, daughter of a long time vegetarian showed severe neurological issues after birth.
Similar to the man above, doctors immediately started treating her with B12 injections. Luckily in this case, the child improved significantly after several injections, but she continued to show signs of developmental issues as she aged.
A B12 deficiency can have potentially irreversible consequences and affect all ages. Although rare, it can happen to anyone.
Use these stories as a lesson to keep up a regular supplementation schedule.
Health Benefits of Vitamin B12
Vitamin B12 is essential for the functioning of our blood cells, the brain, or DNA. Research has also linked it to the reduction of diseases like dementia and heart disease.
Needless to say, it’s amazing.
Along with the above, these are more health benefits of Vitamin B12:
- Forms red blood cells
- Helps boost mood and fight depression symptoms
- Prevents birth defects
- Supports healthy skin, hair, and nails
- Keeps your mouth healthy
Research continues to grow around this fascinating vitamin. In particular, with the prevention or reversal of neurological related diseases (aka brain disease).
No conclusions of its efficacy have been proven, but researchers are hopeful for the future.
Food Sources of Vitamin B12
Vitamin B12 is found naturally in animals foods including meat, fish, poultry, eggs, and milk products. However, it’s most prevalent in the specific foods outlined below.
Best animal foods with Vitamin B12:
- Beef Liver
- Wild Rainbow Trout
- Sockeye Salmon
- Light Tuna Fish, canned in water
Vegan and vegetarian B12 food sources are much more scarce. Even though B12 is found in sea vegetables, it is an unreliable source due to impostor enzymes.
These impostor enzymes are not active in the body and can sometimes alter blood tests to show higher levels of Vitamin B12 in the blood stream. Therefore, the two options below are the best food sources for vegans.
Best vegan foods with Vitamin B12:
- Nutritional Yeast
- Vitamin B12 Fortified foods (like plant milk or cereal)
Nonetheless, due to the unreliable nature of food sources, supplements are still recommended as best practice for vegans and vegetarians.
Read about The Best Vitamin B12 Foods for Vegetarians and Vegans
How Much Vitamin B12 Do You Really Need?
These recommendations come from the Food and Nutrition Board at the Institute of Medicine of the National Academies. They will meet the needs of 98% of healthy people.
However, those with unique medical conditions should speak with their doctor for specific dosing protocols.
Recommended Daily Intake (RDA) for Healthy Adults:
- 2.4 mcg per day
Additionally, pregnant women need slightly more at 2.6 mcg per day and lactating women need 2.8 mcg per day.
Most Vitamin B12 supplements start at least 250 mcg and go as high as 5000 mcg per dose.
As you can start to see, a once daily or once weekly supplement will more than satisfy the RDA.
Choose one of the two dosing guidelines for Vitamin B12:
- 250 mcg per day OR
- 2500 mcg per week
Typically, people choose the once per week option because most supplements come in higher doses. With that, you will find the best value for your dollar and can avoid supplementing with pills daily.
It’s also best to take Vitamin B12 supplements during the day since they stimulate the nervous system and can cause a caffeine-like effect in the brain.
Some people report trouble sleeping if taken too late in the day. As a rule of thumb, take the supplement before 1 p.m.
Learn more about What Supplements Vegans Need
Is Vitamin B12 Dosage 5000 mcg Safe?
In fact, 5000 mcg of Vitamin B12 supplementation is a safe dosing amount. Although, you do not need to consume that much.
With the RDA at only 2.4 mcg for healthy adults, taking 5000 mcg just creates expensive urine. You can safely dose at lower levels and still reach the RDA.
Moreover, our bodies can store Vitamin B12 in our tissues for several years, so overloading is unnecessary.
In other words, more is not better when dosing for Vitamin B12.
The only exception that would make sense dosing at 5000 mcg (daily or weekly) is if you are receiving treatment from a B12 deficiency. Likewise, if you have a health condition that affects absorption rates.
In either of those scenarios, you would be working with a health professional to set up a proper dosing protocol.
Best Vegan Vitamin B12 Supplements
Whether you prefer chewable, liquid, or sublingual, all forms work.
There is some evidence showing sublingual absorbs more efficiently into the bloodstream, but it’s not enough to shun all other forms of Vitamin B12 supplements.
To make your decision easy, use this vegan friendly supplement list below:
Top Five Best Selling Vegan Vitamin B12 Supplements on Amazon
- Jarrow Formulas Methylcobalamin B12 (2500mcg)
- VeganSafe B-12 – Organic Liquid Vegan Vitamin B12 (2500mcg)
- Deva Vegan Vitamin B-12 Fast Dissolve Lozenges (1000mcg)
- Mega Food Vegan B12 – Supports Healthy Eenergy Levels (500mg)
- Vegan Vitamin D3+B12 Gummy by MaryRuth’s Made (250)
One thing to note is that many non-vegan ingredients can sneak into B12 supplements. While it’s always best to seek vegan-approved labels, there is not one regulated standard agency.
The most common non-vegan ingredients used in B12 supplements:
- Intrinsic Factor
Other ingredients that could be either animal or plant-based (usually the label with state the difference):
- Magnesium Stearate
- Stearic Acid
Due to strict false-advertising regulations, labels that claim a Vitamin B12 supplement is vegan friendly will be the case.
Vitamin B12 Wrap-Up
If you are a vegan or vegetarian, you must supplement with Vitamin B12. Otherwise, you run the risk of developing serious conditions later in your life such as dementia, blindness, or even death.
Just like buying insurance for your vehicle, use Vitamin B12 as an insurance policy for your health.
Unless you have specific medical condition that calls for large amounts of Vitamin B12 supplementation, dosing at 5000 mcg is worthless. Our bodies can absorb an adequate amount through a methylcobalamin containing Vitamin B12 supplement at 2500 mcg on a weekly basis or 250 mcg daily.
Anything more is flushing your hard-earned dollars down the toilet.
By the way! If you want to test your B12 levels, click or tap here to get 25% off a Vegan Nutritional Maintenance panel that you can do in the comfort of your own home!
I was diagnosed with low white blood cells. The complete blood test checking everything including HIV came out negative. But my B12 vitamins was normal but right on the edge to be on the lower side. Since he couldn’t think of any other reason my Dr recommended B12, he said sometimes this could be the reason. He prescribed the injection but couldn’t afford it and he put me on sublingual 5000 mcg methylcobalamin instead. When I knew about this website I had already bought vegan EZ MELTS. My diet was mostly a lot of vegetables and fish occasionally chicken and very rarely beef. I am over 60 and could feel like having a little hard time remembering things but not that bad. EZ Melts is not on your recommended list but I chose it because I wanted to avoid gelatin. Thank you for your informative article.
Hi Abu, I am happy to hear you are working with your doctor for your low white blood cell count. All the product recommendations in this article are vegan friendly (meaning no gelatin). Feel free to order one of them the next time you need to replenish your Vitamin B12 supplement.
Is it dangerous to overdose on sublingual B12? What will happen?
Great question Fair Haven Farms. It’s highly unlikely anyone could overdose on B12 because No Tolerable Upper Intake Level (UL) has been established by the FDA. Additionally, since it’s a water soluble vitamin, any excess B12 will get excreted through the urine.
Speaking of excreting b12 in the urine; does it alter the urine color? I notice urine coloration with nutritional yeast (strong yellow), but not with 5,000 mcg Methylcobalamin liquid drop (sublingual)… Hmmm, is the b12 quality different on these two, therefore excretion is somehow different?
Typically taking a B-complex vitamin alters the urine color (due to Vitamin B2 specifically). However there have been cases of high B12 intake changing urine color. If you feel it’s serious, I recommend speaking to your doctor about it.
Is it best to take B12 5000 mcg every 2 weeks?
Great question Angela. It is recommended to take 2500mcg weekly. Even though that equates to 5000mcg bi-weekly, all of the medical recommendations I’ve come across stick to a weekly supplement.
Do you take ones a week or everyday of the week
Yes I recommend taking one 2500mcg per week (unless otherwise noted by your doctor)
Thank you for a great article. I am 74 and reasonably fit with the exception of the unreasonable fatigue at times. Mostly mid-mornings. Plus a few other of the symptoms. Nothing serious yet thank goodness except a non-existent memory. I have been a vegetarian for over 40 years. The thinking then was B12 for the first two years till the body made its own. DUH!! So, not too late for a recovery, I hope. Any additional suggestions. ?
Hi Andy. It’s never too late. Based on the research I did for this article, I would take one 2500 mcg B12 pill once per week unless you have been told my a doctor to supplement using more. It seems to be the most effective for the general population. Does that help answer your question?
Me hice unas analiticas hace poco y mi nivel de vitamina b12 está en 2,000
No había caído en cuenta que estaba tomando pastillas sublinguales casi diario eran de 5000 mcg
que debo hacer para que mi cuerpo bote el exceso de vitamina b12 y en cuanto tiempo debo hacerme otras analiticas para saber si han bajado los niveles.
por supuesto suspendi inmediatamente la ingesta de las vitaminas
El exceso de vitamina B12 se elimina a través de nuestra orina, por lo que no hay nada más que deba hacer. Me gustaría volver a probar después de 30 días de cambiar su ingesta. Sin embargo, según las recomendaciones de los profesionales médicos, debe complementar con 2,500 mg de vitamina B12, una vez por semana.
I’ve been taking quick dissolve vitamin B12 5,000 mcg daily. My energy has gone through the roof. Is this too much?
I love how I feel on it but after reading about does daily or weekly….this is an extreme amount I’m taking daily. Is there harmful side effects that can occur over time?
Hi Kerri. I would recommend 2500mg weekly (based on the recommendation of medical professionals). From my research, there are no negative side effects because your body excretes any extra that it doesn’t need.
I have been taking b12 for the last 5 years taking a 5000mcg daily and the lowest I have taken is 1000 but not too often. Recently I took a annual blood test and my b12 was elevated to 1400. My doctor told me to hold for a few months. taking the 5000 daily has obviously raised my levels. Everything else was in normal range. Have you ever heard of this?
Hi Stacy. I have heard of excess B12 in the system. Your doctor is correct in that you should lower your dosage to allow your levels to come down to normal.
Hola , yo tengo un vitamina B12 syblingual de 5000 mcg, entonces estaría bien q tome la mitad la pastilla cada semana?
¡Si, eso es correcto!
Hello. I have found that if I feel nervous during the day I would take one or two 2500 mcg of B12 and it relaxes me. The past few days I have been experimenting with taking it before bed to help me sleep. I still get up during the night to go to the bathroom and sometimes stay awake for an hour, but I have been sleeping more soundly and having more dreams, which is one of the things I am trying to do…sleep more soundly and go into REM. What do you think of this?
I would definitely not take it before bedtime. B12 activates areas of the brain that help keep you awake. Although it’s possible it could affect people differently.
Iam a type 2 diabetic, i take Metformin 1000 twice daily. I have started taking 5000 mcg vitamin B12 daily as I heard that Metformin lowers the B12 . Without the B12 i have no energy, am I doing right?
Hi Audrey. Great question! Yes you are doing it right. Research has shown that metformin can decrease B12 levels in as little as 3 months. I would recommend working closely with your doctor to get regular B12 blood tests to make sure your levels stay in the normal range.
Does it work if you take a 5000mcg B12 pill every 2 weeks??
The math makes sense. However to be safe, I would take 5000mg once per week
Richard J Wims
5000mcg or 5000mg? the vitamin I have has mcg is there an equivalent?
How does one really know if the advertised mcg level is accurate?
By calling the company and confirming.
Is there a noticeable difference between 500mcg and 1000mcg supplements?
In energy levels or effectiveness?
I can’t digest milk,I don’t eat meat . I stopped eating eggs too for November 2020, I started reducing weight , went to blood test because iam feeling weak . Result is B12 levels is 382 pg/ml.(borderline ). Iam taking 1000mcg daily sublingual b12 since 5 days ,still feeling weak . Can I take 5000mcg daily b12?
If the RDA of B12 is so very low, why do pharma companies make the dosages thousands times higher? Is it just the appearance that more is better? I understand that there is little risk of taking such high doses (within reason of course). Thanks!
Hi Scotty just found your site and it’s very informative. I’m a little confused about how often to take B12 5000mcg. Is it daily, weekly or biweekly? Thank you for your time.
Hi Scotty, i have been taking PPI for Gerd for over 5 years and found out that PPI makes it difficult for me to absorb B12. My doctor suggest me to take 5000mcg daily but my urine starts to have bubble, is it too much to handle for my kidney? Do you have any suggestions for me? Many thanks.
Hi, Scotty , it is okey to take vitamins b12 5000 mcg on empty stomach ? Thank you in advance for your reply😊. God bless!
Is a daily dosage of 1ml (liquid form) appropriate?
Yes you can take this daily
Hello. I am vegan and my b12 level in blood is normal. However my nutritionist suggested supplement which contains methylcobalamin 5000 mcg, hydroxycobalamin 2000mcg and Folate 5440mcg , to take daily plus B complex. It sounds like too much to me. Any suggestions?
Methylcobalamin. This is assuming you have no underlying health conditions that would would make the other supplements required. Always talk with your doctor when changing up supplement routines.
When I was younger I occasionally got B-12 shots for anemia. Now that I’m older I just take a high absorption methylcobalamin tablet daily. I’ve also taken 1000 mcg per day and didn’t notice any difference in energy level. As a runner I need to keep my B-levels up. I also take a B-complex. I do not eat red meat, primarily fish and chicken but I read that certain foods like light tuna in water and sockeye salmon do contain B-12 vitamin.
Most people won’t feel any energy boost from B12. It’s more of a nervous system increase vs boost you’d get from caffeine. I’d suggest eating mainly whole foods for your vitamins and using the supplement as insurance. Stick to whole grains, legumes. nuts/seeds, fruits, and dark leafy greens for B vitamins.
Really like how you are bring this information about B12 to us our here. I’m a 61 yr old totally active guy, climate change activist and bike mobility guru that has been dealing with progressive numbness in my toes, feet and lower legs and now my finger tips and hands that started 3 months ago and 9 days after my second Covid jab. I live in Vermont where the practitioners really don’t really seem to have a handle on B12. My first B12 blood test showed 373.3 pg/mL, but that was after I was dosing on B12 for 5 days and then over 2000 pg/mL 3 weeks later in a subsequent test. My PCP recommended I stop the B12 which I did, but I am going back to it. Incidentally, my methylmelonic test was 0.19 nmol/mL. I also have a low vitamin D levels at 18 ng/mL which I cam now supplementing for.
I know you can’t be “my doctor”, but I’m just wondering if you have any further words of wisdom. I’ve done all sorts of other blood tests and everything has come up normal.
How long I can take B12 5000mg.Please, dosage B12 daily or weekly.
Once weekly is more than enough for those who have normal blood work. If you have any pre-existing conditions, please check with your doctor first.
I have facial nuralgia. Will it hep if I take 5000 b12?
Should I take it daily?
2500mcg per week
Banana peanut butter
Hello handsome Scotty,
I have some underlying conditions and in need of high dose of b12.
I am taking 5000 mcg tablet in methylcobalamine form..
Do you think i can supplement it daily for a year then go down to a thousand mcg next year as a maintenance?
Cause ive found these B12 2000mcg in methylcobalamine with adesonylcobalamine form that id like to try after this 5000 mcg supplementation.
I’d like to hear your opinion in details if you can pls. Thank you so much for helping us sweety. 😉
I’m getting vitamin b12 injections once a month cause my level was at 320. Do I still need to take a b12 pill form supplement daily if I’m already getting injections?
That would be something you would want to confirm with your doctor.
Can I stop taking 1000mg of B-12 and start taking 5000mg? And would 5000mg be too much?
This is very specific to your needs. However, typically any excess B12 excretes through the urine. So unless it’s an insane amount of “more”…in this case I don’t see that, you should be okay.
My B12 level was 186 item on a regimen of daily 1,000 infections for awful. Then once a awful for the weeks then jointly for maintenance. Item a vegetarian. I eat no meat. With the infections I’m supplementing 1000 B12 daily. As i start monthly injections what amount of oral B12 would you recommend?
I have been diagnosed with ” MTHFR” and low B12 several years ago, after a few decades of intermittent fatigue, joint pains, numbness and tingling…. and was subsequently advised to take B12 vitamins among others. I have read that it is ok to have high B12 numbers if you are supplementing, but I see that you have advised people to cut down B12 if their blood levels are high. If excess B12 is being flushed from the system anyway, then could it be OK to continue with the 5,000 mcg dose weekly or biweekly if I am now feeling energized, more focused, symptom free, and calm?
Hi Scotty, how long before you start noticing the effect of B12 supplement one is taking? Like a week or two? Thank you for your good work.
You probably won’t notice any major differences when taking B12. I personally didn’t notice anything different.
Oxygen and Hydrogen is methyl group 🤔
Hi Scotty, can I add my B12 drops https://shopwellabs.com/products/wellabs-vitamin-b-12-drops to me salad or smoothie, for example? Or only under the tongue?
Either or is find. Under tongue is for fastest absorption
I had low b12 and was put on 5000 mcg daily. Now my b12 level is 2000+.
Is that normal?
that is something you’ll want to check with your doctor. Excess B12 typically gets excreted through urine and is harmless.
Hi, I brought both 2500mcg and 5000mcg in a liquid form
Which is better to take and should I have it daily or weekly.
2500mcg is all that is required weekly
sir can i take three thousand mcg
vitamin b12 every day ,
is it dangerous
From the research I’ve gathered, no. Excess B12 gets excreted through the urine.
I take Sublingual 1000 mcg a day
Hi my dr did my blood work and said my b12 is ok but always I feel dizzy and tired I talked to my dr he said I can hav b12 vitamin but didn’t told me how much mcg I just finish my one bottle didn’t know how much mcg tht but I was feeling ok with that but u suggest I can continue with tht and I m vegetarian
I can’t suggest because this is individual for you. But the research clearly demonstrates that 2,500 mcg weekly is adequate. Feeling dizzy and tired can be from a host of issues. Before looking at vitamins, I’d recommend ensuring you’re drinking enough water each day (70 oz +) and sleeping 7-9 hours per week. Do that for a month and then reassess your symptoms.