Cyanocobalamin
Prescription status is set country by country — the label where you live is the one that applies.
Beta: the medication section is still being tested, and its data may contain errors. Do not rely on it for a decision about your own treatment.
Cyanocobalamin is a synthetic form of vitamin B12, sold over the counter. B12 is a cofactor in the conversion of homocysteine to methionine and in the maturation of red blood cells, so a shortage shows up as a macrocytic anaemia and as neurological symptoms. It is used to correct or prevent documented deficiency, and is often taken for fatigue attributed to low levels.
A usual adult range, not a national label — the dose and the timing differ by country and by product.
Approved uses differ by country — some of these may be off-label or unapproved where you live.
It is absorbed with or without food, and the morning is the conventional time. The relevant follow-up is in the laboratory rather than in how it feels: serum vitamin B12 rises, homocysteine falls when it was elevated by deficiency, and haemoglobin and mean cell volume drift back toward normal over weeks to months as the marrow recovers. Because levels can look adequate while stores are not, repeat testing rather than symptoms is what shows whether it is working.
See a doctor if numbness, tingling, unsteadiness, or memory trouble appear or persist, since neurological deficiency needs assessment rather than a higher supermarket dose, and if anaemia does not improve on repeat blood counts.
Reference information, not medical advice. Discuss any change with your doctor.