Serious and sometimes fatal infections may develop owing to bacterial, mycobacterial, invasive fungal, viral, or other opportunistic pathogens reported; may cause reactivation of latent TB or viral infections (see Black Box Warnings and Dosing Considerations) Consider risks and benefits before initiating in patients with chronic or recurrent infection, history of serious or opportunistic infection, underlying conditions predisposing them to infection, or patients who have been exposed to tuberculosis or have resided or traveled in areas of endemic tuberculosis or mycoses (see Black Box Warnings) Consider TB therapy for patients with a negative test for latent TB but who have risk factors for TB infection; consultation with a physician with expertise in TB recommended to aid in decision about whether initiating anti-TB therapy is appropriate If a new infection develops during treatment, promptly initiate diagnostic tests appropriate for an immunocompromised patient; if necessary, initiate appropriate antimicrobial therapy and closely monitor; interrupt baricitinib therapy if patient unresponsive to treatment If herpes zoster occurs, interrupt treatment until episode resolves Malignancies were observed in clinical studies; non-melanoma skin cancers (NMSCs) reported; periodic skin examination is recommended for patients who are at increased risk for skin cancer Perform screening for viral hepatitis in accordance with clinical guidelines before starting therapy; unknown impact on chronic viral hepatitis reactivation Increased incidence of thrombosis, including DVT and PE, observed compared with placebo; caution in patients at increased risk of thrombosis (see Black Box Warnings) Gastrointestinal perforation reported in clinical studies, although the role of JAK inhibition in these events is unknown May increase incidence of neutropenia, lymphopenia, anemia, or elevated LFTs or lipids; monitor laboratory values at baseline and periodically during treatment