Fatigue after a tough day at work or a particularly grueling bout of physical activity is normal. But being consistently tired, weak to the point of exhaustion, moody or foggy mentally could be a signal from your body that something is wrong.

First, find out what’s causing the energy drain. Are you getting enough sleep or battling depression? Focus on the quality of your diet and exercise, experts advise. For example, eat foods with sugars that the body absorbs slowly (also known as low-glycemic), such as whole grains, high-fiber vegetables, nuts and healthy oils, such as olive oil, suggest experts from the Harvard Medical School.

If the tiredness lingers past two weeks, book an appointment with your doc to get tested for conditions that may be to blame, such as anemia or hormonal deficiencies. “There are many different diagnostic tests available today,” says Eva Cwynar, MD, an endocrinologist and author of the book The Fatigue Solution. “Some must be done in a doctor’s office, and some you can do at home.”

These tests can determine whether you’re lacking key nutrients or suffer from chemical imbalances that rob the body of vitality. In addition, a checkup can help determine whether the problem is a side effect of medications you take to treat allergies, blood pressure or some other health issue.

Don’t give up, Cwynar stresses. Look into the matter.