Injectable vitamin B12 can be purchased without a prescription from several online sources, including ushcgshots.com, b12-shot.com and aminopharmaceuticals.com. These websites ship within the United States and offer both needles and syringes. Injectable vitamin B12 is only available for purchase from pharmacies in the United States with a prescription.
Medical providers may recommend vitamin B12 supplements when there is an indication of vitamin B12 deficiency, explains WebMD. While most vitamin B12 is consumed through diet, poor nutrition, gastrointestinal issues and various diseases may lead to deficiencies that require supplementation.
Vitamin B12 deficiency can lead to anemia, unusual weakness, constipation and nerve damage, according to WebMD. In cases of serious vitamin deficiency, doctors may prescribe regular injections, patches, or topical creams. Injections may be given daily, weekly or monthly, depending on the level of deficiency in the patient, explains WebMD.
While there is no evidence that vitamin B12 supplements can prevent heart disease or improve energy and athletic performance, research suggests that high levels of dietary vitamin B12 may prevent dementia in older patients.
Vitamin B12 is not known to have harmful side effects but may interact with drugs used to treat peptic ulcer disease, acid reflux, diabetes and some antibiotics, according to the National Institutes of Health.