Some types of bradycardia produce no symptoms, and others may cause dizziness, weakness or fainting (syncope). The most serious forms of bradycardia (e.g., complete heart block) are medical emergencies that could lead to convulsions or sudden cardiac death. People are encouraged to read more about a specific bradycardia of interest to learn its symptoms.

The baseline electrocardiogram is the main test to diagnose bradycardia. In some case bradycardia and heart block may be intermittent, and some tests that monitor heart rhythm may be required to detect these abnormalities, such as 24-hour EKG (Holter) monitoring or event recorder.