Blood pressure varies from one person to another. A drop as little as 20 mmHg, can cause problems for some people. There are different types and causes of low blood pressure.

Severe hypotension can be caused by sudden loss of blood (shock), severe infection, heart attack, or severe allergic reaction (anaphylaxis).

Orthostatic hypotension is caused by a sudden change in body position. This occurs most often when you shift from lying down to standing. This type of low blood pressure usually lasts only a few seconds or minutes. If this type of low blood pressure occurs after eating, it is called postprandial orthostatic hypotension. This type most often affects older adults, those with high blood pressure, and people with Parkinson disease.

Neurally mediated hypotension (NMH) most often affects young adults and children. It can occur when a person has been standing for a long time. Children usually outgrow this type of hypotension.

Certain medicines and substances can lead to low blood pressure, including:

Other causes of low blood pressure include: