Methylcobalamin is a cofactor in the synthesis of serotonin to melatonin. Melatonin is the sleep hormone.

You could try taking your B12 every other day, during drowsy times.

Do you take your B12 on an empty stomach? This is the ideal way.

Some people get drowsy when they consume sugar and alot of carbohydrates at meals or snacks. If you eat mostly protein for breakfast and lunch, you should be more alert. Carbs stimulate serotonin, which can make people sleepy. Have more carbs at your last meal of the day...to promote sleep. If you study at night, limit carbs at dinner, and no sugar!

Eating large meals will release high insulin levels, and this induces sleepiness too. Smaller meals with snacks spread out during the day may prevent sleepiness. Snacks that are good are cheese, nuts, nutrition bars like Zone Perfect which are balanced, peanut butter, eggs, etc.