Symptoms of low blood pressure, medically known as hypotension, relate to decreased blood flow to many areas of the body. Symptoms can include

fainting (syncope),
dizziness, or
a feeling of lightheadedness.

Decreased blood flow to the coronary arteries results in symptoms of angina, including chest pain. With low blood pressure, the heart rate may be elevated or irregular. Fast breathing, weakness, fatigue, cold skin, pale skin, confusion, nausea, or vomiting can occur, depending upon the reason for the low blood pressure. Other symptoms can include

blurred vision and
increased thirst.

Shock (in which all major body organs are deprived of oxygen) occurs with severe hypotension.

Causes of low blood pressure (hypotension)

Low blood pressure has many causes, including a reduction in blood volume due to bleeding or other conditions, heart diseases such as heart attack or heart failure, and certain medications. Shock is a condition characterized by severely low blood pressure; this is often a result of septicemia (bacterial infection of the bloodstream). Dehydration due to vomiting, diarrhea, or excessive sweating causes a loss of body fluid and can lead to low blood pressure. Blood pressure also tends to decrease in pregnancy.