Direct inhibition of H+ ion excretion to the gastric lumen makes proton pump inhibitors (PPI) the most effective drugs against gastric acid-related diseases. Over recent years usage of proton pump inhibitors has increased dramatically. Due to the low costs, high efficacy and rarity of adverse effects, their use is prevalent and often it does not correspond with existing medical guidelines. The literature lists stress ulcer prophylaxis among patients with low risk of bleeding, routine 'gastroprotective' medication during treatment and non-specific abdominal symptoms as the most common patterns of off-label PPI use. This article summarizes the influence of PPI therapy on gastric mucosa, absorption and occurrence of adverse effects. The authors note that their low awareness among physicians contributes to wide and imprudent use of drugs of this group.