The Pressure in our Blood Arteries falling below Normal Levels is what Low Blood Pressure is.
The normal range of human Blood Pressure is 120/80 mm Hg
This, many times is a result of not having enough food, or skipping meals altogether or due old age. Also caused due improper functioning of digestive system, and/or indulging in excess sexual activity. Feeling of being unsuccessful in life or uselessness or hopelessness, palpitations due excess fear etc. Additionally, few more reasons could be dehydration (excessive loss of body fluids), Hormonal problems (Thyroidism), Low Blood Sugar Levels (Hypoglycaemia), Anaemia, Anorexia and yes, side effects of the Great Allopathic Medicines! The symptoms are feeling Dizzy, Fatigued, Slow Heartbeat, Walking Slow, Stressed all the time, Hands/Feet Getting Cold.
Ayurvedically, Low Blood Pressure is simply Vitiation of Vata (The Nerve Force) & Pitta (The Body Metabolism), and is easily curable