SIDE EFFECTS: This medication can cause weight gain, changes in appetite, stomach upset, diarrhea, gas, trouble sleeping, decreased sexual ability/desire, or fever. Women may experience changes in their menstrual periods, including unpredictable bleeding. If any of these effects persist or worsen, inform your doctor promptly.

Remember that your doctor has prescribed this medication because he or she 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 immediately if any of these rare but serious side effects occur: fast/pounding heartbeat, headache, swelling of hands/feet, fatigue.

Seek immediate medical attention if any of these rare but very serious side effects occur: chest pain, confusion, mental/mood changes, weakness/numbness on one side of the body, pain/redness/swelling of arms or legs, slurred speech, trouble breathing, severe or sudden vision changes.

A very serious allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of a serious allergic reaction include: 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.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Read the Megace ES (megestrol acetate) Side Effects Center for a complete guide to possible side effects »

PRECAUTIONS: Before taking megestrol, tell your doctor or pharmacist if you are allergic to it or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: adrenal gland problems (e.g., Cushing's syndrome), blood clots, congestive heart failure, diabetes, high blood pressure, kidney problems, unusual vaginal bleeding.

High blood sugar (hyperglycemia) and worsening of diabetes may occur. Symptoms of high blood sugar include thirst, increased urination, confusion, drowsiness, flushing, rapid breathing, or fruity breath odor. If these symptoms occur, tell your doctor immediately. People with diabetes should monitor their blood sugar levels more frequently when they start taking this medication and whenever the dose changes since they may need to change their doses of diabetic medications.

This drug may decrease adrenal gland activity. Make sure you tell your doctors and dentists of your megestrol use and when you stopped using it. After stopping this drug, additional corticosteroids (e.g., prednisone or hydrocortisone) may be necessary in stressful situations such as trauma, major surgery or serious infection. Consult your doctor or pharmacist for details. Symptoms of adrenal problems include unusual weakness, dizziness, nausea and rapid weight loss.

Kidney function declines as you grow older. This medication is removed by the kidneys. Therefore, elderly people may be more sensitive to this drug and to its side effects.

This medication must not be used during pregnancy. Megestrol may cause harm to your unborn baby. If you become pregnant or think you may be pregnant, inform your doctor immediately. Women of child-bearing age should use an effective form of birth control while using this medication. Consult your doctor for more details.

It is unknown if this drug passes into breast milk. Breast-feeding while using this drug is not recommended. Consult your doctor before breast-feeding.