B12 how many mcg

Be aware that sublingual and dissolvable B supplements often contain sugar substitutes that can cause gas, bloating, and diarrhea in some people -- particularly if taking multiple pills. You can use the Ingredients listings in CL's Review to spot and avoid these ingredients. In general, it's best to avoid excessive doses of any vitamin if it is not needed. Get more information, including the Recommended Daily Allowance for B by age and gender , differences in the forms of B, potential side-effects and drug interactions, plus ConsumerLab.

Join today to unlock all member benefits including full access to all CL Answers and over 1, reviews. Join now at www. Find out if taking B vitamin supplements can reduce the attraction of mosquitoes to people.

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Are they necessary if I have a B12 deficiency? What is vitamin B12 and how much do I need? Do vitamin patches, such as for B12 or multivitamins, really work? How about those from PatchMD? Can you absorb vitamin B12 through patches? Which supplements reduce the risk of stroke? Which increase the risk of stroke? What B-vitamin complex do you recommend for older people? Which foods are a good source of B vitamins?

I read on your website that some B vitamins cause diarrhea due to added sugar substitutes like sorbitol. I stopped mine and my diarrhea stopped immediately. Which B doesn't contain sorbitol? What do I need to know about taking B vitamins?

What do you think? Is sublingual vitamin B, which is placed under the tongue and allowed to dissolve, really better than the pill form? I thought the B vitamins were all water soluble and did not build up in the body, so you would not build up toxic levels. Am I wrong?

Can taking too much vitamin B-6 be dangerous? My doctor told me to stop taking supplements because my kidney function was low. After stopping, my kidney function returned to normal. Can taking a lot of supplements really damage the kidneys? I'm over 50 and looking to take a vitamin B supplement.

Many contain a form of vitamin B called cyanocobalamin, yet I read on the Internet that this form is toxic. Should I be concerned? How likely are Americans to be deficient in vitamins or minerals? Related Reviews 1 B Vitamin Supplements. First Name. Email Address. I want to subscribe to ConsumerLab news emails, and I understand that I will have the option to become a full member in the next step.

Continue to Join. Join the conversation. Submit comment Saving…. What about B12 in energy drinks? Is that the same as taking tablets or getting injections?

Nancy December 18, Kathryn July 2, David December 8, JL July 20, David January 4, Dr Wm Martin July 6, Dr Wm Martin July 8, Just so I'm clear: The test subjects had both diabetes and advanced kidney disease?

Rose June 19, I take 1 mg. B12 sublingual 2 x a day. It has really helped with the ringing in my ears. John August 24, Marsha October 3, Susan March 8, Some of us take more time to switch over to European ways! Virginia March 23, I appreciated this contribution and am glad to also have read the commentary to it. Henry March 29, Ronald December 4, Bruce June 12, My doctor says she is happy with my B level.

John May 11, In fact, B12 may be easier to absorb in supplement form. If you're over 50 years of age, have acid reflux, or have been told by your doctor that your body has trouble absorbing B12, aim for mcg per day to give your body a better chance of absorbing what it needs.

Don't worry about overdoing it -- there's no upper limit on B12, which means there's no evidence that high levels up to 1, mcg are harmful. Scientists hypothesize that elevated homocysteine levels might have a negative effect on the brain via numerous mechanisms, including cerebrovascular ischemia leading to neuronal cell death, activation of tau kinases leading to tangle deposition, and inhibition of methylation reactions [ 77 ]. Most observational studies have found correlations between low serum vitamin B12 concentrations alone or in combination with high folate concentrations and poor cognitive function [ ].

However, a few observational studies have found no such association [ 85 , 86 ]. In addition, according to a systematic review of 35 prospective cohort studies in 14, participants aged 47 to years followed for an average of 5. Although homocysteine concentrations declined significantly more by 5. A Cochrane review of vitamin and mineral supplements to maintain cognitive function in cognitively healthy people included 14 studies that compared folic acid, vitamin B12, vitamin B6, or a combination of these supplements to placebo in 27, participants, most of whom were aged 60 years or older [ 92 ].

The supplements had little to no effect on global cognitive function when administered for up to 5 years and also appeared to have no impact when administered for 5 to 10 years. A Cochrane review evaluated the effects of vitamin and mineral supplements on cognitive function and dementia in people with mild cognitive impairment [ 93 ].

The review included 5 trials with participants that investigated B vitamin supplements one study of folic acid only, and four trials of vitamins B6 and B12 and folic acid. Taking these B vitamins for 6 to 24 months had no apparent effect on episodic memory, executive function, speed of processing, or quality of life, although one study found a slower rate of brain atrophy over 2 years. Additional clinical trials are needed to better understand the effects of vitamin B12 supplementation on cognitive function and cognitive decline.

Energy and endurance Because of its role in energy metabolism, vitamin B12 is often promoted as an energy enhancer and an athletic performance and endurance booster. However, vitamin B12 supplementation appears to have no beneficial effect on performance in the absence of a nutritional deficit [ 94 , 95 ]. Even at large doses, vitamin B12 is generally considered to be safe because the body does not store excess amounts.

Vitamin B12 has the potential to interact with certain medications. In addition, several types of medications might adversely affect vitamin B12 levels. A few examples are provided below.

Individuals taking these and other medications on a regular basis should discuss their vitamin B12 status with their healthcare providers. These drugs are used to treat gastroesophageal reflux disease and peptic ulcer disease. They can interfere with vitamin B12 absorption from food by slowing the release of gastric acid into the stomach and thereby lead to vitamin B12 deficiency [ ].

Metformin Metformin, an antihyperglycemic agent used as first-line treatment for prediabetes and diabetes, might reduce the absorption of vitamin B12 and significantly reduce serum vitamin B12 concentrations [ 98 ].

In some cases, fortified foods and dietary supplements are useful when it is not possible otherwise to meet needs for one or more nutrients e. For more information about building a healthy dietary pattern, refer to the Dietary Guidelines for Americans and the U. Department of Agriculture's MyPlate. This fact sheet by the Office of Dietary Supplements ODS provides information that should not take the place of medical advice. We encourage you to talk to your healthcare providers doctor, registered dietitian, pharmacist, etc.

Any mention in this publication of a specific product or service, or recommendation from an organization or professional society, does not represent an endorsement by ODS of that product, service, or expert advice. Updated: April 6, History of changes to this fact sheet. Find ODS on:. Strengthening Knowledge and Understanding of Dietary Supplements. Health Information Health Information. Carmel R.

Cobalamin vitamin B Modern Nutrition in Health and Disease. Allen LH. Vitamin B Encyclopedia of Dietary Supplements. London and New York: Informa Healthcare; Adv Nutr ; Present Knowledge in Nutrition. Washington, DC: Elsevier; J Nutr ;SS. Vitamin B12 deficiency: Recognition and management. Am Fam Physician ; Biomarkers and algorithms for the diagnosis of vitamin B12 deficiency.

Front Mol Biosci ; Age-specific reference ranges are needed to interpret serum methylmalonic acid concentrations in the US population. Am J Clin Nutr ; Vitamin B12 deficiency. Nat Rev Dis Primers ; Nutrients ; Foods and supplements associated with vitamin B 12 biomarkers among vegetarian and non-vegetarian participants of the Adventist Health Study-2 AHS-2 Calibration study.

Vitamin B12 concentrations in milk from Norwegian women during the six first months of lactation. Eur J Clin Nutr ; Food and Drug Adminstration. Systematic review on daily vitamin B12 losses and bioavailability for deriving recommendations on vitamin B12 intake with the factorial approach.

Ann Nutr Metab ; Bioavailability of vitamin B Int J Vitam Nutr Res ; Dietary sources of vitamin B and their association with plasma vitamin B concentrations in the general population: the Hordaland Homocysteine Study. Plasma vitamin B concentrations relate to intake source in the Framingham Offspring study. Department of Agriculture.

FoodData Central. Food and Drug Administration. Dietary Supplement Label Database. Paul C, Brady DM. Comparative bioavailability and utilization of particular forms of B 12 Supplements with potential to mitigate B 12 -related genetic polymorphisms. Integr Med ; How I treat cobalamin vitamin B12 deficiency. Blood ; A single-center, double-blinded, randomized controlled study to evaluate the relative efficacy of sublingual and oral vitamin B-complex administration in reducing total serum homocysteine levels.

J Altern Complement Med ; Those with megaloblastic anemia, delirium or dementia, celiac, Crohn's disease, or sometimes pregnant women.

Vitamin B12 deficiency is usually treated by supplemented B12, either in pill form or as injections. A deficiency of vitamin B12 can contribute to your developing a type of anemia called megaloblastic or pernicious anemia.

Because vitamin B12 is used in the production of red blood cells and the maintenance of the nervous system, a deficiency can cause your body to manufacture inadequate red blood cells.

Pernicious anemia may have no symptoms and occurs most frequently in people who suffer either from an autoimmune disorder or who have a disease of malabsorption that prevents their bodies from absorbing enough vitamin B Treatment for this type of anemia depends on its severity, but usually involves B12 supplements.

If you aren't taking a B12 supplement, toxicity isn't an issue. Since B12 is a water-soluble vitamin, it won't build up in your body.

There are some situations in which you should not take supplements or high doses of vitamin B If you have Leber's disease, large doses of vitamin B12 could lead to damage in your optic nerve and even blindness.