Japanese patients often describe their pain with ideophones (sound-symbolic, imitative words), such as biribiri ‘having a continuous electric shock’. However, some manuals for healthcare workers recommend avoiding using these words in their interactions with patients, assuming that they are too subjective. We examined how reliable pain ideophones are in comparison with pain metaphors, such as denki-ga hashiru-yoona itami ‘pain like an electric current running through one’s body’. In Experiment 1, Japanese speakers rated visually presented pain ideophones and metaphors on 15 semantic-differential scales (e.g., strong–weak, momentary–continuous). It was found that the ratings of ideophones and metaphors equally varied between participants. In Experiment 2, Japanese speakers did the same rating task for a selected set of pain ideophones and metaphors presented auditorily in sentence frames. The results show that ideophones were rated more consistently than metaphors across participants, and this was true for various prosodic/morphological variants of ideophones (e.g., biriiit-to ‘having a sudden, great electric shock’, biribirit-to ‘having a momentary repetitive electric shock’). These findings indicate that ideophones can be more reliable than metaphors in health communication, especially when placed in proper context.