People with heart failure usually need to monitor their weight carefully. A sudden weight gain may mean that excess fluid is building up in your body because your heart failure is getting worse. As heart failure progresses, most people gain weight in parallel with the development of congestive symptoms. The amount of weight gained varies greatly among people with heart failure, and it reflects the amount of sodium and water the body has retained.
In some cases, weight gain may be the first noticeable sign that you have developed heart failure or that your heart failure is getting worse. In fact, your doctor will want you to track your weight to monitor your heart failure and to help gauge the effectiveness of treatment.
Your doctor likely will work with you to develop some guidelines to follow for managing ups and downs (fluctuations) in weight caused by fluid retention. For example, if you have a weight increase of 2lb, your doctor may recommend taking an additional diuretic that day.
WebMD Medical Reference from Healthwise