Ask your consultant doctor,how to set your doses.your treating Doctor is the right person to give you correct advice in this regard.
Next Steps
Consult your doctor as early as possible to decide on doses.
Health Tips
you said, because of shift duty ,most of time you skip breakfast, which is in long term not desirable to maintain good health.
workout with your spouse to have suitable breakfast,which you can manage at workplace even.eg.having one banana,apple or nuts or anything of your choice