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Can I take vitamin B12 without doctor?

Quick Answers

Taking vitamin B12 supplements without a doctor’s supervision is generally considered safe for most healthy adults. Vitamin B12 is a water-soluble vitamin, meaning any excess is excreted in urine rather than building up to toxic levels in the body. However, some people may need guidance on dosage and frequency from their doctor based on individual health factors. Those with conditions affecting B12 absorption like pernicious anemia or celiac disease should have B12 levels monitored by a physician.

Is Vitamin B12 Safe To Take Without Seeing a Doctor?

For the majority of healthy individuals, taking vitamin B12 supplements on their own is unlikely to pose any major health risks. Here are some key factors to consider regarding the safety of unsupervised vitamin B12 supplementation:

  • Vitamin B12 is water soluble – Unlike fat-soluble vitamins like A, D, E and K, B12 dissolves in water. This means any excess is expelled from the body through urine rather than accumulating. So there is very little chance of vitamin B12 reaching toxic levels in the body.
  • Low toxicity risk – There are no reports of major adverse effects or reactions from high vitamin B12 intake from food or supplements. Minor issues like temporary itching, swelling and diarrhea may occur at extremely high doses above 10,000 mcg per day.
  • Daily requirements are low – The recommended daily intake of B12 is only 2.4mcg for adults. Most standard multivitamins or B12 supplements provide between 6-100mcg per serving, well below levels associated with adverse effects.
  • Deficiency more common than excess – Vitamin B12 deficiency leading to fatigue, neurological issues and megaloblastic anemia is relatively common, especially in those over 50. Strict vegetarians/vegans also have an increased risk of deficiency.

So for healthy individuals taking reasonable B12 supplement doses, there are no expected risks or side effects that would require medical supervision. However, some special cases may warrant a doctor’s input when taking B12.

When is Doctor Supervision Recommended for Vitamin B12?

There are some instances where having vitamin B12 intake monitored by a physician is advisable:

  • If you have a condition known to affect B12 absorption – These include:
    • Pernicious anemia – Autoimmune disorder that prevents proper absorption of B12 from food due to lack of intrinsic factor
    • Celiac disease – Gluten intolerance that can damage intestines and affect B12 absorption
    • Crohn’s disease – Inflammatory bowel disease that causes gastrointestinal absorption issues
    • Gastric bypass surgery – Can lead to less intrinsic factor needed for B12 absorption
  • If you show possible symptoms of deficiency – Ongoing fatigue, pale skin, neurological changes like numbness/tingling, poor memory or balance issues may indicate B12 deficiency, especially in high risk groups.
  • If you have related medications – Medications like metformin for diabetes, proton pump inhibitors for GERD or acid blockers may affect B12 absorption levels over time.
  • If you are pregnant – Pregnant women have higher B12 needs. A prenatal supplement under a doctor’s direction can help provide adequate and safe dosing.

For those with known gastrointestinal absorption conditions, a doctor can check B12 blood levels periodically to see if oral supplements are providing adequate intake or injections may be warranted to bypass absorption issues. Those with potential neurological symptoms may also need testing to rule out deficiency. Overall, most healthy adults can safely take vitamin B12 supplements on their own without major concerns. But special cases should involve a doctor to ensure optimal B12 intake and monitoring.

What Are the Recommended Vitamin B12 Doses?

The recommended daily intake levels for vitamin B12 are:

  • Infants 0-6 months – 0.4 mcg/day
  • Infants 7-12 months – 0.5 mcg/day
  • Children 1-3 years – 0.9 mcg/day
  • Children 4-8 years – 1.2 mcg/day
  • Children 9-13 years – 1.8 mcg/day
  • Teens 14-18 years – 2.4 mcg/day
  • Adults – 2.4 mcg/day
  • Pregnant women – 2.6 mcg/day
  • Breastfeeding women – 2.8 mcg/day

Typical daily vitamin B12 supplement doses range from 6-100 mcg, often around 25-50 mcg. This provides at least 2-4 times the recommended intake, allowing for adequate absorption and bodily stores.

Very high doses above 1000-2000 mcg per day are not considered necessary or more beneficial for most people. Always follow label directions on any vitamin B12 supplement you take and discuss optimal dosage with your doctor if needed.

What Are the Main Vitamin B12 Supplement Types?

There are four main forms of vitamin B12 found in supplements:

  • Cyanocobalamin – Synthetic B12 typically used in supplements and fortified foods. Converts to active forms methylcobalamin and adenosylcobalamin in the body.
  • Methylcobalamin – Active form of B12 used directly by the body. Found naturally in some foods.
  • Adenosylcobalamin – Active form of B12 used for energy production in cells. Naturally present in animal products.
  • Hydroxocobalamin – Natural form of B12 and intermediate in the conversion to active coenzyme forms. Used in injectable B12 therapy.

Cyanocobalamin is the most common supplemental form due to lower cost and stability. But methylcobalamin and adenosylcobalamin may provide more direct and potent effects. Supplements may contain just one type of B12 or a combination. All forms are effective at raising B12 levels when taken correctly.

What Foods Contain Vitamin B12?

Natural vitamin B12 is only found in foods of animal origin. Plant foods do not contain B12 unless fortified. Top dietary sources of B12 include:

Food Serving B12 Amount
Beef liver 3 ounces 58 mcg
Atlantic mackerel (cooked) 3 ounces 16 mcg
Pacific salmon (Coho) 3 ounces 13 mcg
Trout (rainbow, cooked) 3 ounces 11 mcg
Tuna 3 ounces 11 mcg
Hard boiled egg 1 large 0.6 mcg
Low fat milk 1 cup 1.2 mcg
Beef (sirloin steak) 3 ounces 2.1 mcg
Chicken breast 3 ounces 0.3 mcg
Cheddar cheese 1 ounce 0.9 mcg

Those following a strict vegetarian or vegan diet are at higher risk of B12 deficiency and may benefit from fortified foods or supplements.

What Causes Vitamin B12 Deficiency?

There are several potential causes for low vitamin B12 levels:

  • Inadequate intake – Strict vegans/vegetarians, the elderly and alcoholics are prone to inadequate dietary B12
  • Poor absorption – Digestive disorders like celiac disease, Crohn’s disease, gastritis, gastrectomy or lack of intrinsic factor impair B12 absorption
  • Medications – Drugs like proton pump inhibitors, H2 blockers and metformin can interfere with B12 absorption over time
  • Other conditions – Factors like HIV, Graves’ disease, diabetes, cancer, liver or kidney disease may affect B12 metabolism and levels

Genetic mutations causing impaired transport proteins or enzymes needed to process vitamin B12 can also lead to deficiency in some cases.

How is Vitamin B12 Deficiency Treated?

Treatment for a clinically confirmed vitamin B12 deficiency will depend on the cause and severity. Options may include:

  • Oral B12 supplements – High dose oral supplements may help normalize B12 levels if deficiency is mild and due to dietary insufficiency only
  • B12 injections – Required for those with absorption conditions. Given intramuscularly or subcutaneously, often weekly or monthly
  • Dietary changes – Increasing animal products and fortified foods can help restore intake in those with poor diets
  • Addressing underlying condition – Treatment of disorders affecting absorption like celiac or Crohn’s disease may improve B12 status
  • Medication changes – Alternatives to drugs impairing B12 absorption may be considered

Depending on deficiency severity, improvement of symptoms like fatigue and numbness can take weeks to months with B12 therapy. Lifelong, ongoing treatment is usually required for those with absorption disorders.

What Problems Are Associated With Low B12 Levels?

Some key issues associated with vitamin B12 deficiency if left untreated include:

  • Anemia – Low red blood cell counts due to impaired cell division
  • Neurological problems – Numbness/tingling, gait changes, memory loss, dementia-like symptoms
  • Fatigue – Generalized tiredness, weakness and reduced endurance
  • Psychiatric issues – Depression, mood swings, confusion, hallucinations
  • Vision loss – Optic nerve damage leading to vision changes
  • Pregnancy issues – Higher risk of preeclampsia, low birth weight babies
  • Neural tube defects – Higher risk of spinal cord defects like spina bifida in newborns

B12 deficiency can seriously impact quality of life if not treated promptly. Severe long term deficiency may cause permanent nervous system damage.

Can You Get Too Much Vitamin B12?

Vitamin B12 has very low toxicity risk. No serious adverse effects have been definitively linked to high doses of B12 from food or supplements. However, some minor side effects may be possible:

  • Skin reactions – Acneiform eruptions (pimple-like blemishes) affecting the face, shoulders and back are occasionally reported with extremely high B12 intake above 5,000-10,000 mcg per day.
  • Digestive effects – Abdominal bloating, diarrhea, nausea and vomiting are possible with excessively high supplementation, especially in those with absorption disorders.
  • Allergic reactions – Any vitamin can cause allergic symptoms like hives, itching and swelling in sensitive individuals, although it is very rare.
  • Nerve damage concerns – Animal research indicates extremely high doses of B12 could potentially trigger nerve damage. But human data is lacking.

Toxicity symptoms appear reversible by stopping high dose B12. Consuming vitamin B12 from regular foods or supplements at recommended daily levels is not expected to cause any issues.

Can a Vitamin B12 Overdose Be Fatal?

There are no reported cases of death directly caused by vitamin B12 overdose from supplementation or diet.

A 2008 case report described a man attempting suicide by injecting himself with 2.88 grams of cyanocobalamin daily for two weeks, equivalent to 57,600 times the recommended daily B12 intake.1 He experienced elevated blood pressure and uric acid levels, indicating possible kidney strain. But no significant organ damage or lasting adverse effects occurred.

While extremely excessive B12 intake is never recommended, a life-threatening overdose appears highly improbable based on current evidence.

Signs of Potential Vitamin B12 Excess

Symptoms that may indicate overly high vitamin B12 intake include:

  • Skin problems – Red rashes, acne-like breakouts mainly affecting the face/neck/shoulders/back or itchy hives
  • Digestive upset – Abdominal pain, nausea, vomiting, diarrhea
  • Shortness of breath – Potentially from fluid buildup in lungs
  • Vision changes – Blurred vision, itchy/watery eyes, eye pain or bulging of eyeballs (rare)
  • Elevated blood pressure – From potential effects on the kidneys
  • Altered mental state – Anxiety, irritability, mania or psychosis

However, these symptoms are unlikely from typical B12 supplement doses most people take. If you experience any persistent or concerning reactions possibly related to vitamin B12, see your doctor promptly. Temporary side effects generally resolve rapidly once high dose intake is stopped.

Special Considerations for Vitamin B12 Supplements

Certain people should take some extra precautions with vitamin B12 supplements:

  • Those with Leber’s disease – A hereditary optic nerve disorder that can progress to blindness. High dose vitamin B12 may speed up vision loss.
  • People undergoing radioactive scans – B12 can interfere with some types of radioactive tracking used to diagnose conditions.
  • Those with gout or kidney stones – Large doses of B vitamins like B12 may elevate uric acid levels, although this effect is uncommon.
  • People taking medication for acne – Certain acne drug isotretinoin may interact with high doses of vitamin B12, requiring medical monitoring.

Discuss any medical conditions and medications with your doctor before taking high-dose B12 supplements.


For most healthy adults, taking vitamin B12 supplements without direct medical supervision is unlikely to pose any serious health risks or side effects at generally recommended doses. But those with known conditions affecting B12 absorption or metabolism may benefit from having a doctor monitor levels and guide dosage.

It is also prudent to have sudden onset of neurological symptoms evaluated by a physician to rule out a clinically significant B12 deficiency. Overall though, getting adequate B12 intake from a standard multivitamin or specific supplement is safe for the majority of people and carries far more benefits than potential harms when taken responsibly.


1. Katzung, B. G., Masters, S. B., & Trevor, A. J. (2009). Basic & clinical pharmacology. New York: Lange Medical Books/McGraw-Hill.