It is argued that the introductory use of the epistemic disclaimer jag vet inte ‘I don’t know’ in responsive turns and turn-constructional units does not chiefly exhibit speaker's knowledge deficit, but rather indicates interactional problems depending upon epistemic asymmetries between interactants. Epistemic tensions, notably in Swedish doctor–patient interactions, are treated by the lay party deploying epistemic disclaimers. These can start off a change in epistemic stance towards a more autonomous, more personally precise knowledge formulation that anywise opposes the professional party's suppositions.