Health status is theoretically conceptualised as a dynamic outcome that evolves over time along the lifecycle; most inequalities studies focus on snapshots of inequality and rarely consider health inequality over the lifecycle. Measuring inequality over the lifecycle requires dealing with two dimensions: ages and individuals. One can measure inequality over the lifecycle by firstly aggregating health over ages and then measuring inequality by aggregating over individuals; this is the lifecycle perspective. Otherwise, one can measure inequality over individuals at each age and then aggregate inequality over ages; this is the age-specific perspective. This paper proposes a methodology to measure health inequality over the lifecycle from both the age-specific and lifecycle perspectives. We use data from a British cohort study and focus on self-assessed health and death as measures of health. We use first order stochastic dominance and Hammond dominance criteria to respect the ordinal and qualitative nature of those health outcomes and measure health inequality. Our results show that the two perspectives impact on the existence and the magnitude of inequalities of opportunities in health in the UK. While the lifecycle perspective provides a global view of inequality of opportunity, the age-specific perspective highlights (i) a change in the dynamic of inequality of opportunity favoring people born in South-East UK in the second part of their lifecycle, (ii) a reinforcement of inequality of opportunity between regions over the lifetime.