Nonsteroidal anti-inflammatory drugs (including diclofenac) may rarely increase the risk for a heart attack or stroke. This effect can happen at any time while using this drug but is more likely if you use it for a long time. The risk may be greater in older adults or if you have heart disease or increased risk for heart disease (for example, due to smoking, family history of heart disease, or conditions such as high blood pressure or diabetes). Do not use this drug right before or after heart bypass surgery (CABG). Also, this drug may rarely cause serious (rarely fatal) bleeding from the stomach or intestines. This side effect can occur without warning symptoms at any time while using diclofenac. Older adults may be at higher risk for this effect. Stop using diclofenac and get medical help right away if you notice any of the following rare but very serious side effects: stomach/abdominal pain that doesn't go away, black/bloody stools, vomit that looks like coffee grounds, chest/jaw/left arm pain, shortness of breath, unusual sweating, confusion, weakness on one side of the body, sudden vision changes, trouble speaking. Talk with your doctor or pharmacist about the benefits and risks of using this medication.

Skin irritation/redness may occur at the application site. If this effect lasts or gets worse, tell your doctor or pharmacist promptly. Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects. This medication may raise your blood pressure. Check your blood pressure regularly and tell your doctor if the results are high. Tell your doctor right away if you have any serious side effects, including: signs of kidney problems (such as change in the amount of urine), symptoms of heart failure (such as swelling ankles/feet, unusual tiredness, unusual/sudden weight gain). This drug may rarely cause serious (possibly fatal) liver disease. Get medical help right away if you have any symptoms of liver damage, including: nausea/vomiting that doesn't stop, loss of appetite, stomach/abdominal pain, yellowing eyes/skin, dark urine. A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: fever, swollen lymph nodes, rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing. This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist. In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch. In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Some products that may interact with this drug include: aliskiren, ACE inhibitors (such as captopril, lisinopril), angiotensin II receptor blockers (such as losartan, valsartan), cidofovir, corticosteroids (such as dexamethasone, prednisone), lithium, methotrexate, other products applied to treated skin, water pills (diuretics such as furosemide). This medication may increase the risk of bleeding when used with other drugs that also may cause bleeding. Examples include antiplatelet drugs such as clopidogrel, "blood thinners" such as dabigatran/enoxaparin/warfarin, erlotinib, among others. Check all prescription and nonprescription medicine labels carefully since many medications contain pain relievers/fever reducers (aspirin, NSAIDs such as ibuprofen, naproxen, or ketorolac). These drugs are similar to diclofenac and may increase your risk of side effects if taken together. However, if your doctor has told you to take low-dose aspirin to prevent heart attack or stroke (usually 81-162 milligrams a day), you should keep taking the aspirin unless your doctor tells you not to. Ask your doctor or pharmacist for more details.