Methycobal is a Vitamin B12 Substance. Methycobalamin is the neurologically active form of vitamin B12. Used in the treatment of Alcoholic neuropathy, Drug induced neuropathy, Diabetic neuropathy, Peripheral neuropathy. The standard single dosage is 500 mcg. (depends on your absorption ability). There are no current FDA safety problems with it.
Do you have a deficiency to require it?
There can be side effects, especially if you are consuming too much. That is why it is important to know what your current levels are.
As a less expensive solution, a dietary change can help.
The top 10 natural sources for B-12 are:
1: Clams, Oysters, and Mussels
3: Caviar (Fish Eggs)
6: Crab and Lobster
8: Lamb (Mutton)
10: Eggs (goose egg is higher than chicken eggs)
As for mcg-iu conversions, An International Unit measures activity of vitamins and drugs. Vitamins A, D, and E are often measured in this way. Conversion from IU to mcg is different for each vitamin. The various B vitamins would have to be calculated or converted differently.
You should also know how much you are absorbing. If I take 500 mcg per day but only absorb 2 mcg, I would not be getting the minimum of 4 mcg of B-12 per day.
I hope this helps!