Like primary hypertension, secondary hypertension usually has no specific symptoms, even if blood pressure has reached dangerously high levels. For people diagnosed with high blood pressure, having any of these signs may mean the condition is secondary hypertension: 
High blood pressure that doesn't respond to blood pressure medications (resistant hypertension)
Very high blood pressure — systolic blood pressure over 180 millimeters of mercury (mm Hg) or diastolic blood pressure over 120 mm Hg
High blood pressure that no longer responds to medication that previously controlled the blood pressure
Sudden-onset high blood pressure before age 30 or after age 55
No family history of high blood pressure
No obesity
