The study is a United Kingdom (UK) based multi-centre study which will evaluate the impact of a medication optimisation intervention (delivered in GP practices by pharmacists to patients at risk of medication related problems), on healthcare resource utilisation and patient outcomes. Pharmacists in 4 areas across the UK (3 in England and 1 in Northern Ireland) will engage with patients, thought to be at a higher risk of medication related problems, within their GP practice in order to help identify areas for improvement