AbstractObjectivePrevious studies on thyroid function and risk of infection is conflicting and often stem from intensive care cohorts were nonthyroidal illness syndrome (NTIS) may be present. The objective of this study was to identify the risk of bloodstream infections (BSI) and BSI‐related mortality with thyroid‐stimulating hormone (TSH) levels within the reference range in a general population.DesignProspective follow‐up.ParticipantsThe HUNT2 (1995‐97) included 34,619 participants with information on TSH levels.MeasurementsHazard ratios (HRs) with 95% confidence interval (CI) confirmed BSIs and BSI‐related mortality until 2011.ResultsDuring a median follow‐up of 14.5 years, 1179 experienced at least one episode of BSI and 208 died within 30 days after a BSI. TSH levels within the reference range of 0.5–4.5 mU/L were not associated with the risk of first‐time BSI, with an HR of 0.97 (95% CI: 0.90–1.04) per mU/L. Stratified by baseline age < or ≥65 years, TSH was inversely associated with the risk of BSI (HR: 0.88; 95% CI: 0.78–1.00 per mU/L) in the youngest age group only. Persons with any baseline thyroid disease had a 30% risk and the hyperthyroid subgroup a 57%, and hypothyroidism a 20% increased risk of BSI. TSH levels were not clearly associated with BSI mortality, but the HRs were imprecise due to few BSI‐related deaths.ConclusionThere was some evidence of a weak inverse association between TSH levels and the risk of BSI in persons below 65 years of age. The increased risk seen in persons with thyroid illness is probably explained by confounding by concurrent ill health.