Licorice, through the effects of glycyrrhizic acid (GA), raises blood pressure (BP). The World Health Organization has suggested that 100 mg GA/d would be unlikely to cause adverse effects, but of 13 previously published studies none have been randomized and controlled and independently quantified the GA content. Our aim was to analyze the effects on home BP of a daily licorice intake containing 100 mg GA. Healthy volunteers were randomly assigned to start with either licorice or a control product in a nonblinded, 2 × 2 crossover study. Home BP was measured daily, and blood samples were collected at the end of each 2-wk period. There were 28 participants and no dropouts. The median age was 24.0 y (interquartile range 22.8–27.0 y). During the licorice compared with control intake period, the systolic home BP increased mean difference: 3.1 mm Hg (95% confidence interval CI: 0.8, 5.4 mm Hg) compared with −0.3 mm Hg (95% CI: −1.8, 1.3 mm Hg); P = 0.018 and renin and aldosterone were suppressed mean change: −30.0% (95% CI: −56.7%, −3.3%) compared with 15.8% (95% CI: −12.8%, 44.4%); P = 0.003; and −45.1% (95% CI: −61.5%, −28.7%) compared with 8.2% (95% CI: −14.7%, 31.1%); P <0.001, respectively. In the quartile of participants with the most pronounced suppression of renin and aldosterone, N-terminal prohormone of brain natriuretic peptide concentration increased during the licorice compared with control period mean change: 204.1% (95% CI: −11.6%, 419.7%) compared with 72.4% (95% CI: −52.2%, 197.1%); P = 0.016. We found licorice to be more potent than previously known, with significant increases in BP, after a daily intake of only 100 mg GA. Thus, the safe limit of intake of this substance might need to be reconsidered. This trial was registered at clinicaltrials.gov as NCT05661721 (https://clinicaltrials.gov/study/NCT05661721).