In a 2013 study in 100 older adults, supplementing with 500 mcg of vitamin B12 for 8 weeks was found to normalize B12 levels in 90% of participants. Higher doses of up to 1,000 mcg, or 1 milligram (mg), may be necessary for some ( 13). Pregnant people

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products). If you have severe anemia, this medication may rarely cause low potassium levels in the blood ( hypokalemia) as your body makes new red blood cells. Tell your doctor right away if any of these serious side effects occur: muscle cramps, weakness, irregular heartbeat.You should not use Vitamin B12 if you are allergic to cyanocobalamin or cobalt, or if you have Leber's disease (an inherited form of vision loss). Cyanocobalamin can lead to optic nerve damage (and possibly blindness) in people with Leber's disease. It plays a crucial role both in muscle gain and endurance performance. Adverse effects of vitamin B12 deficiency

Vitamin B12 is an essential nutrient that plays a critical role in several of your body’s processes. Vitamin B12, in the forms of cyanocobalamin and hydroxycobalamin, can be administered parenterally as a prescription medication, usually by intramuscular injection [ 2]. Parenteral administration is typically used to treat vitamin B12 deficiency caused by pernicious anemia as well as other conditions (e.g., tropical sprue, pancreatic insufficiency) that result in vitamin B12 malabsorption and severe vitamin B12 deficiency [ 5]. Before taking cyanocobalamin, tell your doctor or pharmacist if you are allergic to it; or to any form of vitamin B12; or to cobalt; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details. However, 1000 mcg daily dosing of cyanocobalamin was able to normalize the MMA concentrations in patients with pernicious anemia. Active people, athletes and fitness enthusiasts should be very mindful of their vitamin B12 concentrations as well. Low levels may cause serious adverse effects, including fatigue, muscle weakness, pain, or cramps!The average vitamin B12 level in the breast milk of women with vitamin B12 intakes above the RDA is 0.44 mcg/L [ 14]. The U.S. Food and Drug Administration (FDA) specifies that infant formulas sold in the United States must provide at least 0.15 mcg vitamin B12 per 100 kcal [ 15]. You have pernicious anemia. This autoimmune condition affects the stomach's ability to produce intrinsic factor, so you can't absorb vitamin B12 through your digestive system. Symptoms of B12 deficiency

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Vitamin B12 injection only for the indication prescribed. While cyanocobalamin is the most common form found in supplements, there is no research to suggest that one specific form is more effective or readily absorbed. Your dose needs may change if you become pregnant, if you breastfeed, or if you eat a vegetarian diet. Tell your doctor about any changes in your diet or medical condition.

Vitamin B12 is found mostly in animal products, including meats, seafood, dairy products, and eggs. It’s also added to some processed foods, such as cereal and nondairy milk. Another study has concluded that 1,000 mcg of oral cyanocobalamin each day in the beginning, later on the weekly dose and followed by monthly are equally effective as 1,000 mcg of IM cyanocobalamin.