Caffeine is one of the most used substance all over the world. Ideally it should be consumed as less as possible. Find out Long Black vs Doppio caffeine content in the following sections. However Long Black Caffeine levels and Doppio 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 Long Black vs Doppio, their side effects and benefits.