In 2025, the population is all individuals aged 15 years or older in the State. A stratified sampling approach was used to select approximately 26,500 respondents aged 15 years and over from the Census 2022 frame. The sample was stratified into six groups based on responses to the Census 2022 question on general health status: Very good, Good, Fair, Bad, Very bad, and Not stated. To ensure sufficient representation of those in poorer health, the Very bad health stratum was intentionally oversampled relative to its proportion in the population. Within each stratum, individuals had an equal probability of selection. The Irish Health Survey has a weight variable to correct for non-response and sampling error. The weighting procedure had two steps: non-response adjustment and calibration. Design weights were calculated for all people in the initial sample. The design weights are computed as the inverse of the selection probability of the unit and were the same for all sampled due to the simple random sampling approach. The purpose of design weights is to eliminate the bias induced by unequal selection probabilities. Calibration of the non-response adjusted design weights then took place, calibrating to the Q4 2025 population estimates at the level of sex, five-year age group, and NUTS 3 region using the Icarus-macro, developed by INSEE, for this purpose. To provide national population results, the survey results were weighted to represent the entire population.