Caffeine is one of the most used substance all over the world. Ideally it should be consumed as less as possible. Find out Irish Breakfast Tea vs Flat White Coffee caffeine content in the following sections. However Irish Breakfast Tea Caffeine levels and Flat White Coffee Caffeine levels may differ with their brands, quantity of additives used, types of additives used etc. Below we have given you a generalized idea of safe levels of caffeine in Irish Breakfast Tea vs Flat White Coffee, their side effects and benefits.