Possible side effects of diclofenac sodium include heartburn, nausea, upset stomach and diarrhea, according to WebMD. Diclofenac sodium may also cause gas, constipation, drowsiness or headache. Some people may feel dizzy after taking diclofenac sodium. Individuals should speak to a physician or pharmacist if side effects worsen or persist.
Diclofenac sodium may cause blood pressure to rise, notes WebMD. Other side effects that are rare but serious include sudden or unexplained weight gain, swelling of the feet or hands, painful or difficult swallowing, and auditory problems, such as ringing in the ears. Some people may feel unusually tired after taking diclofenac sodium. Diclofenac sodium may cause shifts in a person's mood or mental state. Individuals should see a doctor right away if any of these side effects occur.
Other serious side effects that require immediate medical attention include an unexplained stiff neck and a change in the amount of urine, states WebMD. Although it happens rarely, diclofenac sodium can cause a potentially lethal liver disease. Signs of a damaged liver include yellowing skin or eyes, dark urine and persistent nausea, loss of appetite, vomiting or pain in the abdomen or stomach.
Signs of an allergic reaction to diclofenac sodium include difficulty breathing, severe dizziness and a rash, notes WebMD. An allergic reaction may cause itching or swelling, especially in the throat, tongue or face.