Headache, diarrhea, weakness, nausea, gas, loss of appetite, and dizziness may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly. To reduce the risk of dizziness and lightheadedness, get up slowly when rising from a sitting or lying position. 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. Tell your doctor right away if you have any serious side effects, including: unusual bleeding/bruising, black stools, swelling of the ankles/feet, rapid/difficult breathing, stomach/abdominal pain, unusual tiredness, signs of kidney problems (such as change in the amount of urine, pink/bloody urine), vomit that looks like coffee grounds. Get medical help right away if you have any very serious side effects, including: chest/jaw/left arm pain, confusion/mental changes, severe dizziness, fainting, fast/irregular/pounding heartbeat, seizures, trouble speaking, vision changes, weakness on one side of the body. 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: 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: other drugs that can cause bleeding/bruising (including antiplatelet drugs such as clopidogrel, "blood thinners" such as warfarin/enoxaparin), sucralfate. Aspirin can increase the risk of bleeding when used with this medication. However, if your doctor has told you to take low-dose aspirin to prevent blood clots, 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. Many drugs besides anagrelide may affect the heart rhythm (QT prolongation), including amiodarone, chloroquine, clarithromycin, disopyramide, haloperidol, methadone, moxifloxacin, pimozide, procainamide, among others.