If you have certain health conditions or are taking certain medications, your doctor may tell you to take sildenafil less often. What should I do if I forget a dose? Shake the liquid well for 10 seconds before each use to mix the medication evenly. The information provided is for educational purposes only and is not intended to replace discussions with a healthcare provider. The most common side effects of VIAGRA: headache; flushing; upset stomach; abnormal vision, such as changes in color vision such as having a blue color tinge and blurred vision; stuffy or runny nose; back pain; muscle pain; nausea; dizziness; rash. Be sure to let your doctor and pharmacist know that you are taking these medications before you start taking sildenafil.Cheaper Than Your Copay · No Credit Card RequiredService catalog: Prescription Coupons, Prescription Discounts, Online Doct. Examples of Viagra’s more commonly reported side effects include: headache. flushing (temporary warmth, redness, or deepening of skin color) stuffy nose. indigestion (upset stomach) mild vision. 10K+ visitors in the past month.