High cholesterol can be diagnosed with a simple blood test called a fasting lipid profile, usually taken after you've fasted for 9-12 hours. This test provides four measurements: total cholesterol, HDL or "good" cholesterol, LDL or "bad" cholesterol and triglycerides (another form of fat in your blood).
Everyone ages 20-50 should be tested every 5 years, while those who are over 50 or have specific risk factors should be tested yearly or as often as your doctor recommends.
Regardless of your age, if you've been diagnosed with high cholesterol, you should get tested every 3-6 months, or as your doctor recommends.