Methylcobalamin and cyanocobalamin are two forms of vitamin B12. If you see these long names on different packs, first find the B12 amount per serving and check the units.
Compare the label rows
Write down the form, the amount and what counts as one serving. The amount may appear in micrograms, shown as mcg or µg. The NIH notes that the body can convert cyanocobalamin to active forms. The name alone does not tell you which pack is suitable for you.
Bring the question that matters
If a doctor has asked you to take B12, show the pharmacist or doctor the label you are comparing and ask whether the form and amount match the plan. Find B12 in vegetarian foods · Compare mg and mcg · NIH B12 fact sheet
Make a quick label note
Write down the product name, B12 form and the number of micrograms in one serving. Then check whether the suggested serving is one tablet or more. If you already have a prescription or a supplement at home, put that label beside the new one before asking a pharmacist. This gives them the information needed to answer your question about the specific products you are comparing.