Can you take aspirin and diclofenac together?

This is not recommended. Aspirin and diclofenac are both non-selective NSAIDs (non-steroidal anti-inflammatory drugs). As such they can have side effects that may be additive. The main ones would be stomach ulceration, which may cause bleeding. Kidney problems may also develop. However, many people will take this combination without problems, but the risk of above is higher if on both.