B-12, also called cobalamin, is a water-soluble vitamin essential for the production of red blood cells. Although B-12 occurs naturally in some foods, if you have a deficiency, you may need to take B-12 supplements. Taking B-12 can have some side effects, but making you feel jittery is not a common one.
B-12, one of eight B vitamins, serves several functions in the body. Beside helping to produce red blood cells, B-12 also helps the body convert food into glucose and it aids in the production of genetic material. A B-12 deficiency can result in numbness and tingling in your extremities, disorientation, memory loss, fatigue, confusion and weakness. A B-12 deficiency is more common in older adults than it is in younger people.
According to the Linus Pauling Institute at the University of Oregon, healthy individuals who take more than the recommended dose of B-12 do not generally experience any serious adverse effects. However, every individual reacts differently and Drugs.com documents some gastrointestinal and nervous system side effects. The nervous system side effects include anxiety, dizziness, lack of coordination and nervousness, but the jitters is not specifically documented. Drugs.com notes that these side effects occurred with B-12 injections, not oral supplements.
The National Institutes of Health Office of Dietary Supplements lists the recommended daily allowance of vitamin B-12 by age. For those 14 years or older, the recommended daily allowance is 2.4 micrograms. The recommended amount for pregnant women is 2.6 micrograms per day and for breast-feeding women, it is 2.8 micrograms per day.
MayoClinic.com warns that individuals with certain medical conditions, such as high blood pressure, cardiovascular concerns, dermatologic conditions and low potassium should be cautious taking a vitamin B-12 supplement as you may experience negative side effects. Vitamin B-12 may also react with other medications. Consult your physician before supplementing your diet with B-12 or any other vitamin or mineral, especially if you are pregnant, breast-feeding or have any medical condition.