* This is the Professional Version. Last full review/revision September 2016 by Larry E. Johnson, MD, PhD Drugs Mentioned In This Article * This is the Professional Version. Metformin (brand names Glucophage, Glucophage XR, Fortamet, Riomet, Glumetza, and others) is a popular and highly effective oral diabetes drug used to help manage Type 2 diabetes. This drug works by lowering the amount of glucose made by the liver and by making the body’s cells more sensitive to insulin. Metformin also has some other beneficial effects in that it may help lower blood lipid, or fat, levels (cholesterol and triglycerides) and can, in some people, promote a small amount of weight loss. Metformin can be used with other diabetes pills and with insulin. Side effects of taking metformin are relatively rare, the most common being bloating, nausea, and diarrhea, all of which are temporary. Some people shouldn’t take metformin, including people with kidney disease, liver disease, or congestive heart failure, for example, because of an increased risk of a potentially fatal condition called lactic acidosis.
In recent years, there’s been some concern over the risk of vitamin B12 deficiency in people who take metformin. Vitamin B12 (also known as cyanocobalamin or cobalamin) plays many important roles in the body, such as keeping your blood cells and nervous system in tip top shape. There’s also some evidence that vitamin B12 may help prevent heart disease and possibly even Alzheimer disease (the jury is still out on this one). This vitamin is found primarily in animal foods, such as beef, seafood, eggs, and dairy products, which is why some vegetarians are at risk for a B12 deficiency. Elderly people are often at risk for deficiency as well, due to problems with absorption from the gastrointestinal tract. Symptoms of B12 deficiency include certain types of anemia, neuropathy, memory loss, confusion, and even dementia. So, why would taking metformin possibly put you at risk for a B12 deficiency? According to some studies, between 10% and 30% of people who take metformin on a regular basis have some evidence of decreased B12 absorption.
Researchers aren’t quite sure why this happens. In a study recently published in the October 9 issue of the journal Archives of Internal Medicine,155 Chinese people with Type 2 diabetes taking metformin were identified as having a B12 deficiency, regardless of factors such as age or body weight. The study found that the longer a person had been taking metformin and the higher his daily dose of the drug, the greater his risk of developing B12 deficiency. The authors of the study advocate consideration of vitamin B12 deficiency screening for people who take metformin. While this screening isn’t routine, it’s worth it to have a talk with your health-care provider to see if you’re at risk for deficiency, especially if you’ve been taking metformin for several years or take a high dose. Also, if you have any of the symptoms of B12 deficiency mentioned above, particularly those related to neuropathy (numbness, pain, or tingling in your hands or feet), be sure to let your physician know.
He or she can check the level of vitamin B12 in your blood. Vitamin B12 deficiency can be treated with either oral, injected, or inhaled forms of B12. Some people, such as strict vegetarians or the elderly, may need to take supplements or receive injections on a regular basis. B12 is found in most multivitamin supplements, so it doesn’t hurt to take a multivitamin as a safeguard. However, avoid taking a B12 supplement unless your doctor has prescribed them. Too much vitamin B12 may be harmful, and B12 can also interact with certain medicines. Always let your health-care team know about all medicines and supplements that you’re taking at each visit.Like what you’re reading? Get FREE updates sent to your inbox.Email* I want to improve my...I want to improve my...WeightEnergyDigestionBrainOverall HealthAll of the AboveI hate spam too. Your email is safe with me. Related tests: Vitamin B12 and Folate All content on Lab Tests Online has been reviewed and approved by our Editorial Review Board.
Looking specifically for detail on Vitamin B12 testing? Learn more about ... Send Us Your Comments Get the Mobile App Grading rationaleEvidence gradeCondition to which grade level appliesAMegaloblastic anemia (due to vitamin B12 deficiency)Low levels of vitamin B12 are a cause of megaloblastic anemia, in which red blood cells are larger than normal. Other possible causes include folate deficiency or various metabolic disorders. Anemia should be diagnosed by a physician to address the underlying cause.AVitamin B12 deficiencyStudies have shown that a deficiency of vitamin B12 can lead to abnormal mental symptoms. These symptoms may include ataxia (shaky movements and unsteady gait), muscle weakness, spasticity (stiff or rigid muscles), incontinence (lack of bladder and/or bowel control), hypotension (low blood pressure), vision problems, dementia, psychoses (abnormal condition of the mind), and mood disturbances. Giving vitamin B12 by mouth, by injection, or by nasal inhalation is effective for preventing and treating dietary vitamin B12 deficiency.
CAlzheimer's diseaseSome people diagnosed with Alzheimer's disease have been found to have abnormally low vitamin B12 levels in their blood. The effects of vitamin B12 supplementation on the prevention or progression of Alzheimer's disease remain unclear. More studies are needed before a conclusion can be made.CAngioplasty (opening narrowed/blocked arteries)Some evidence suggests that giving prescription-strength folic acid and vitamins B12 and B6 for six months following coronary angioplasty reduced the risk of overall adverse cardiac events; however, other studies have found this combination to increase restenosis (reoccurrence of narrowing of a blood vessel). CBreast cancerResearchers have reported that women with breast cancer tend to have lower vitamin B12 levels in their blood serum than do women without breast cancer. However, one study found that giving a combination of folic acid, vitamin B6, and vitamin B12 failed to decrease the risk of breast cancer. Further research is needed before conclusions can be made.
CCanker soresVitamin B12 and vitamin B12 injections combined with hydrocortisone were studied to treat recurrent canker sores; although treatment with sublingual vitamin B12 may have some benefit, further research is needed before a conclusion can be made.CCardiovascular disease/hyperhomocysteinemiaHigh homocysteine levels in the blood have been suggested as being a risk factor for cardiovascular disease, blood clotting abnormalities, atherosclerosis (hardening of arteries), heart attack, and stroke (due to a blood clot). Taking vitamin B12 supplements in combination with other B vitamins (mainly folic acid) has been shown to be effective for lowering homocysteine levels. It is unclear whether lowering homocysteine levels has an effect on cardiovascular disease risk and death. More evidence is needed.CCervical cancerSome evidence suggests that vitamin B12 supplementation may have a role in preventing cervical cancer. Further research is warranted in this area.CClaudication (leg pain from clogged arteries)Human research evaluated the effects of vitamin B12 and results demonstrated that although walking distance was improved, sufficient high quality evidence was lacking.
CDepressionA combination of folic acid, vitamin B12, and vitamin B6 lacked any difference in symptoms of depression in older men as compared to placebo. Well-designed clinical trials are needed to confirm any potential benefit.CDiabetic neuropathy (nerve damage)Some evidence suggests that supplementation with vitamin B12 may be helpful in people with diabetic neuropathy. More research is needed in this area.CDiagnostic procedureIn order to detect the presence of vitamin B12, lab tests to measure plasma and serum vitamin B12 may be used; however, many investigators believe testing is unreliable. Research has reported that diagnosis of vitamin deficiencies cannot be made by evaluating vitamin B12 levels alone.CFacial spasmResearch has reported that vitamin B12 lacked any benefit over acupuncture in treatment of facial spasm. CFatigueThere is some evidence that vitamin B12 injections given twice weekly may improve the general well-being and happiness of people complaining of tiredness or fatigue.
Further studies are needed before a conclusion can be made.CFractures (prevention)Some evidence suggests that a combination of vitamins including vitamin B12 may help prevent fractures. CHigh cholesterolSome evidence suggests that vitamin B12 in combination with fish oil may be better than fish oil alone when used daily to reduce cholesterol and triglyceride levels. CImerslund-Grasbeck diseaseVitamin B12 injections may be effective for treating a hereditary form of vitamin B12 malabsorption (Imerslund-Grasbeck disease). Further research is needed to confirm these results.CJoint pain (elbow)Preliminary research suggests that vitamin B12 may be effective for elbow pain, but evidence is lacking. Further research is needed.CMental performanceIncreased homocysteine levels have been associated with lower mental testing scores. However, there was a lack of association between low vitamin B12 blood levels and mental decline, Alzheimer's disease, or dementia. More research is needed before a conclusion can be made.
CPoisoning (cyanide)Hydroxocobalamin (a chemical form of vitamin B12) has been approved by the United States Food and Drug Administration (FDA) since 2006 as a potential antidote for treatment in people with suspected smoke inhalation cyanide toxicity, and although research is lacking on the use of hydroxocobalamin in pregnant women, it did gain FDA approval in pregnant women in 2010. In addition, according to the Australian Resuscitation Council, serious adverse effects with hydroxocobalamin were lacking, and many people with fatal cyanide poisoning had survived.CShaky-leg syndromeClinical reports show that shaky-leg syndrome may be due to vitamin B12 deficiency. CSickle cell diseaseEarly study suggests that a daily combination including folic acid, vitamin B12, and vitamin B6 may reduce endothelial (cells lining vascular walls) damage in people with sickle cell disease. CSleep disorders (circadian rhythm)Taking vitamin B12 by mouth lacked any effectiveness for treating delayed sleep phase syndrome.
Giving vitamin B12 with bright light therapy may be helpful for adolescents with circadian rhythm sleep disorders. DLung cancerOne study found an increase in lung cancer in people with heart disease in Norway whom were taking vitamin B12 and folic acid. More research is needed to better understand this relationship.DStrokeIn people with a history of stroke, neither high-dose nor low-dose vitamin B12 combinations containing vitamin B6, vitamin B12, and folic acid seem to affect risk of recurring stroke. Aging, AIDS, allergies, amyotrophic lateral sclerosis, asthma, autism, bleeding, blood clots, chemotherapy side effects, chronic fatigue syndrome, diabetes, energy level enhancement, growth disorders (failure to thrive), immunosuppression (decrease in immune function), improving concentration, inflammatory bowel disease, kidney disease, Leber's disease, liver disease, male infertility, malignant tumors, memory loss, mood (elevate), mouth and throat inflammation (atrophic glossitis), mental disorders, movement disorders (tremor)