Here are the two main questionnaires currently used to assess Health Anxiety Disorder - the HAI and the HAQ.  The HAI is the one recommended by the NHS Improving Access to Psychological Therapies (IAPT) initiative.  I've also added a scale put together by Adrian Wells that assesses safety behaviours and extent of disease belief.  Finally there is a classic CBT thoughts record.  I don't use these kinds of records much any more, but I've added it for 'completeness'.

Health anxiety inventory (HAI) - the 18 item (short form) HAI is the disorder specific scale recommended by the IAPT initiative.  The third page of the download gives typical scores for a Health Anxiety group, a more general anxiety group, a control group, and so on.   

Health anxiety questionnaire (HAQ) - this 21 item health anxiety questionnaire yields four subscales, which can make it easier therapeutically to target specific behaviours like reassurance seeking.  The third page of the download gives some idea of likely scores in different disorders.

Health anxiety rating scale (Wells) - this health anxiety assessment questionnaire developed by Adrian Wells can be useful, particularly with a CBT approach, when tackling and quantifying safety behaviours like checking and reassurance seeking.

Health anxiety thoughts record - this is a fairly classic cognitive therapy thoughts record adapted for health anxiety.