the exact OH decision will depend on a number of factors, including but not limited to, what medication you currently take and the dose, past or current use of 'rescue' / 'PRN' medication, if you are under secondary care rather than just GP and/or CPN that sort of thing ...
failing to declare stuff to OH is never a good idea, and contrary to mess room / man down the pub gossip , managers do not get to see any part of the OH process, apart from the final report which in the case of pre-employment i s going to be one of four things
1. fit for role with no adaptations
2. fit for role , with no material adaptations , but may be covered by the equality act ( this may be where the OP fits in depending on their history)
3. fit for role with reasonable adaptations
4. not fit for role .