Cyanocobalamin is the most commonly manufactured type of B12 supplement. If you’ve been prescribed these and are curious about how long they take to work, the NHS notes that it might take a few weeks before symptoms like tiredness begin to improve. However, this might vary based on age and severity of symptoms, so it’s always best to speak to your doctor.
According to Drug Bank, cyanocobalamin has various brand names, including B-12, vitamin B12, and Eligen B12. There’s a general mechanism for cyanocobalamin’s effectiveness in the body, regardless of its numerous administration forms. A 2022 study published in the journal Stat Pearls notes that cyanocobalamin attaches to plasma proteins when they enter the bloodstream. The tissues absorb vitamin B12 binding proteins, transcobalamin I and II, and allow them to enter the cells. This leads to a total improvement of megaloblastic anemia and the gastrointestinal manifestations of vitamin B12 deficiency.
The source also establishes that there is also an improvement in neurological symptoms after cyanocobalamin administration. However, the rate of change often depends on the duration and severity of the patient’s B12 deficiency.