How do you know if you are truly dizzy or lightheaded?

Matter of degree: From my experience with thousands of patients the disease "Vertigo" has a spectrum from very mild symptoms to very severe symptoms. In mild form people describe it as lightheadedness or some times repeated episodes of loss of balance. In its severest form the environment spins even at slightest movement and associated with nausea and vomiting leading invariably to hospital visit or admission.