Suicide mortality and mental ill health are increasing globally. Mental ill health can be measured in multiple ways. It is unclear which measure is most associated with suicide risk. This study explored the association between self-rated mental health and medication record and death by suicide. The 2011 Northern Ireland Census records of adults aged 18-74 years (n=1,098,967) were linked to a centralised database of dispensed prescription medication and death registrations until the end of 2015. Mental health status was ascertained through both a single-item self-reported question in the Census and receipt of psychotropic medication. Logistic regression models examined the association between indicators of mental ill health and likelihood of suicide mortality. Of the 1,098,967 cohort members, 857 died by suicide during the study period. Just over half of these deaths (n=429, 50.1%) occurred in individuals with neither indicator of mental ill health. Cohort members with both self-reported mental ill health and receipt of psychotropic medication had the highest risk of suicide (OR=6.13, 95%CI: 4.94–7.61), followed by those with psychotropic medication record only (OR=4.00, 95%CI: 3.28–4.88) and self-report only (OR=2.88, 95%CI: 2.16–3.84). Individuals who report mental ill health and have a history of psychotropic medication use are at a high risk of suicide mortality. However, neither measure is particularly sensitive, as both failed to signal over half of subsequent suicides. Some individuals who report poor mental health but are not in receipt of psychotropic medication are at increased risk of suicide, indicating possible unmet treatment need. The combination of the two indicators offers more precision for identifying those most at risk for targeted interventions.