Causes of Low Blood Pressure: Why Blood Pressure Drops

Low blood pressure is not a diagnosis, but a number. For one person it is an individual norm, for another it is a sign of a malfunction in the heart, blood vessels, or endocrine system. Below — about why blood pressure drops and where the boundary lies between a temporary reaction and a disease.

What is considered low blood pressure and hypotension

Low blood pressure is spoken of when the reading is below 90/60 mm Hg. Some authors define hypotension as a decrease of more than 20 % from usual values or as systolic pressure below 100 mm Hg. The meaning is the same: not only the number matters, but also how far it is below the personal norm.

The mechanics are similar to a water supply system: the pressure in the pipes is maintained by the pump (heart), the volume of fluid (blood), and the lumen of the pipes (vascular tone). If the pump weakens, the fluid leaks out, or the pipes dilate, the pressure will drop.

Blood pressure changes throughout the day. In some people, low readings are constant and asymptomatic — this is their norm. In others, it drops against the background of an illness or medication use. Blood pressure becomes a problem when it causes dizziness, fainting, and in extreme cases — shock.

Physiological causes: sleep deprivation, heat, fatigue, nutrition

Some causes are not related to disease: hereditary predisposition, pregnancy, age. Athletes may have hypotension of training — with constant exertion the body works in an economical mode, the pulse is slower, and blood pressure is lower.

Chronic sleep deprivation, fatigue due to an imbalance between work and rest, stress, and depressive states lead to a decrease in blood pressure. Blood pressure decreases during adaptation to a change of climate, at high altitude, in the tropics, in hot workshops, especially with excessive sweating.

Starvation and a lack of vitamins E, C, B and pantothenic acid can also lead to hypotension. In women, blood pressure may decrease during pregnancy: arterial tone is low during this period.

Blood pressure drops after eating and when changing body position

Two forms are described separately. Orthostatic hypotension — a sudden decrease in blood pressure upon standing up after prolonged squatting or lying down. If symptoms of low blood pressure (dizziness, weakness, nausea) occur upon standing up, this may be orthostatic hypotension. Postprandial hypotension — a drop in blood pressure after eating.

Diseases of the heart, blood vessels, and endocrine system

Acute hypotension is always secondary: myocardial infarction, pulmonary embolism, severe arrhythmias, intracardiac blocks, allergic reactions, blood loss. This condition requires emergency care.

Chronic hypotension can be secondary — against the background of heart failure, decreased function of the thyroid gland and adrenal glands, diabetes, anemia, gastric ulcer, cervical osteochondrosis, traumatic brain and spinal cord injuries. Primary hypotension is distinguished separately as an independent disease; in its development, a major role is assigned to prolonged stress and overstrain.

Most often, low blood pressure is associated with impaired vascular tone: in hypotensive patients, blood vessels constrict and dilate slowly, blood reaches the organs in insufficient volume, and the brain and heart experience oxygen deprivation.

Medications and dehydration as causes of blood pressure drop

Among the causes — a sharp decrease in circulating blood volume: blood loss, burns, dehydration. A drop in blood pressure can be a side effect of certain medications, including overdose in the treatment of high blood pressure. In hot weather and with intense sweating, the volume of fluid in the body decreases.

When low blood pressure requires seeing a doctor

People see a doctor if symptoms recur: dizziness, nausea, blurred vision, general weakness, confusion, fainting. Blood pressure can be measured at home with a tonometer or at a doctor's appointment.

• dizziness upon standing up or a sharp change in body position;
• fainting;
• a tendency to motion sickness, nausea and headache;
• blurred vision, absent-mindedness, worsening memory;
• cold hands and feet, increased sweating.

The doctor determines whether there is a cause that can be corrected and, if necessary, refers for examination; in diagnostics, in particular, a tilt test is used.

Low blood pressure in itself is not a reason to call an ambulance; 103/112 — if blood pressure dropped sharply after blood loss or a burn, if myocardial infarction, severe arrhythmia, or pulmonary embolism is suspected, in an allergic reaction with a sharp drop in blood pressure, in fainting with confusion.

This material is for reference: it does not replace a doctor's consultation — only a doctor can assess the complaints and blood pressure readings and decide whether this is normal or a reason for examination.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer