Introduction: Influenza is an acute viral disease of the respiratory system. Its course can be complicated, particularly in seniors, young children or patients with chronic conditions. Common complications include pneumonia, exacerbation of chronic diseases, heart muscle involvement, and neurologic disorders. This paper analyses the frequency and factors contributing to the development of influenza complications in primary healthcare patients. Materials and methods: The study enrolled a total of 631 adult patients who visited a family physician complaining of respiratory tract infections from January 2019 to April 2020 in the Family Doctor’s Clinic in Gostyń, Greater Poland Province. Of them, 90 patients were diagnosed with influenza. The data sources included patient interviews, physical examinations, results of additional tests, and the patients’ medical files. The diagnosis of influenza was based on the accepted clinical criteria, i.e. a sudden onset of fever + ≥1 clinical symptom in the respiratory system + ≥1 general systemic symptom, lasting <72 hours and confirmed with an Actim Influenza A&B test (Medix Biochemica). Results: Complications of influenza were noted in 13 patients (14%), compared to 77 uncomplicated cases. Four patients required hospital admission. The diagnosed complications included secondary bacterial infection of the lower respiratory tract (61%), exacerbation of chronic diseases (31%), and myocarditis (8%). In logistic regression analysis, asphyxia, wheezing, and crackles were linked to a higher risk of complicated influenza. Conclusions: Complicated influenza occurs significantly more often in patients with multiple comorbidities, including obesity, thyroid diseases, and liver diseases. Clinical symptoms related to the risk of complications include asphyxia, wheezing, and crackles.