Low Blood Pressure: Thresholds, Symptoms, Causes

  • Symptoms: Sometimes none, but often symptoms include palpitations, dizziness, headache, fatigue, shortness of breath
  • Causes: Low blood pressure is partly hereditary. However, it can also be caused by environmental influences, diseases or medication as well as certain body postures or (rapid) changes in position.
  • Diagnosis: Repeated blood pressure measurement, certain circulation tests, if necessary further examinations (such as ultrasound and blood tests). Threshold values: 110 to 60 mmHg in men, 100 to 60 mmHg in women.
  • Treatment: Home remedies and general measures such as alternating showers, exercise, sufficiently salted food, drinking plenty of fluids; if all this does not help: medication
  • Prognosis: Usually harmless, only in certain cases close observation necessary

Low blood pressure: Table of threshold values

The term blood pressure refers to the pressure in the large arteries. These are the vessels that lead away from the heart. How high or low the pressure is inside the arteries depends, on the one hand, on the elasticity and resistance of the vessel walls. On the other hand, blood pressure is influenced by the beating force of the heart – in other words, by how much blood volume is transported into the circulation per heartbeat. Heart rate also plays a role.

In what unit is blood pressure measured?

Blood pressure is expressed in “millimeters of mercury” (mmHg). The upper (systolic) value describes the blood pressure at the moment when the heart muscle contracts and ejects blood. The lower (diastolic) value refers to the relaxation phase of the heart (slackening), when it fills with blood again.

Blood pressure can be calculated using the following formula:

Blood pressure = stroke volume × heart rate × systemic vascular resistance.

So if the body wants to increase blood pressure, one or more of these parameters must be increased. This is how the body then arrives at a higher blood pressure mathematically: it could transport more blood per heartbeat (increase stroke volume), make the heart beat more often (increase heart rate), or make the blood vessels in the body narrower so that vascular resistance increases.

Low blood pressure: values

According to the World Health Organization (WHO), blood pressure should optimally be 120 to 80 mmHg or less. If the systolic value is below 110 (men) or 100 (women) and the diastolic value below 60, this is known as low blood pressure (arterial hypotension). How the upward deviations from the optimal value are assessed can be seen in the table:

Systolic (mmHg)

Diastolic (mmHg)

Low blood pressure (hypotension)

< 110/100*

< 60

< 120

< 80

Normal blood pressure

120 – 129

80 – 84

High normal blood pressure

130 – 139

85 – 89

High blood pressure (hypertension)

≥ 140

≥ 90

* In men, values below 110/60 are considered low blood pressure; in women, values below 100/60.

Low blood pressure is rarely threatening. Only if the values drop too much can low blood pressure become dangerous – then there is a risk of fainting. Occasionally, arterial hypotension is an indication of a potentially serious organ disease.

Low blood pressure: symptoms

Low blood pressure does not always cause symptoms. Especially, however, when blood pressure drops rapidly, symptoms may include dizziness, rapid heartbeat and circulatory problems, headache, or fatigue. Frequently affected are (inactive) adolescents in puberty, young slim women, pregnant women as well as older lean people. In principle, if low blood pressure causes any of the following symptoms – or even several – and they occur frequently or very abruptly, you should have the cause clarified by a doctor:

Palpitations: When blood pressure is low, a rapid heartbeat (pulse) often occurs concomitantly. This is because the body wants to counteract the reduced blood flow – and it does so by making the heart beat faster via activation of the sympathetic nervous system.

Such “dropouts” become dangerous if there is a risk of falling or if they occur while driving.

Headaches: Low blood pressure is often accompanied by (stabbing, pulsating) headaches. The reason: blood flow in the head is reduced. Then it can help to drink something and thereby increase the circulating blood volume. A walk is also good, as the fresh air improves oxygen supply to the brain and stimulates circulation.

Tiredness: Fatigue, concentration problems, drowsiness, tiredness – low blood pressure makes you tired. Those affected take longer to get going in the morning, and they feel listless overall. In addition, they are often shaky or sweat more because of the reduced blood flow.

Shortness of breath: A feeling of tightness in the chest or stitches in the heart area can also be signs of low blood pressure. Some sufferers have trouble breathing, and the skin may feel cool and be pale. This is because arterial hypotension causes blood vessels to become constricted in order to direct blood volume to vital organs such as the heart or brain.

Ringing in the ears, loss of appetite, irritability, sensitivity to the weather and depressive moods can also indicate low blood pressure.

Low blood pressure: causes and risk factors

The kidney also becomes active when the blood pressure in the blood vessels supplying it drops too much: It then releases the hormone renin. It triggers an increase in blood pressure via intermediate steps. Renin, angiotensin and aldosterone are involved in these intermediate steps. These are messenger substances that transmit messages to various parts of the body. The system in the kidney that controls blood pressure via renin is therefore called the renin-angiotensin-aldosterone system (RAAS).

The mechanisms of blood pressure regulation may not function adequately or may be disturbed for various reasons. This results in low blood pressure. Doctors distinguish between different forms of hypotension: primary (essential) hypotension, secondary hypotension and orthostatic hypotension.

Primary hypotension

Primary or essential low blood pressure is the most common form of hypotension. It occurs without an identifiable cause. However, the tendency to it can probably be inherited. Because young, slim people (especially women) often have congenital low blood pressure, this is also referred to as constitutional hypotension (constitution = physique, general physical condition).

Secondary hypotension

Secondary low blood pressure is a consequence or symptom of an underlying disease. These include, for example:

  • Underfunction of the adrenal cortex (Addison’s disease)
  • hypofunction of the pituitary gland (anterior pituitary insufficiency)
  • Heart disease (heart failure, cardiac arrhythmia, pericarditis)
  • Salt deficiency (hyponatremia)Venous insufficiency (varicose veins)

Lack of fluids (in great heat, due to profuse sweating, violent diarrhea and vomiting, etc.) can also cause blood pressure to drop: The large loss of fluid decreases the amount of circulating blood, which decreases the pressure in the vessels. This is the case, for example, in shock. This does not refer to mental shock, but to the lack of volume in the body. This occurs, for example, when a lot of blood or water is lost.

Blood pressure can also drop excessively as a side effect of some medications. Such drug-induced hypotension can be triggered, for example, by:

  • psychotropic drugs (drugs for depression, anxiety, insomnia)
  • Antiarrhythmics (drugs against cardiac arrhythmias)
  • Antihypertensives (drugs against high blood pressure)
  • Diuretics (diuretic drugs)
  • Coronary agents (for angina pectoris: nitro sprays)
  • Vasodilators (vasodilating agents)

Orthostatic hypotension

Possible causes of orthostatic hypotension include:

  • secondary low blood pressuredisturbance of the autonomic nervous system (for example due to diabetes mellitus)
  • Nerve cell damage in the brain (for example, due to Parkinson’s disease, alcohol abuse)
  • Varicose veins (varicosis)
  • Condition following deep vein thrombosis (postthrombotic syndrome)

Two forms of orthostatic hypotension are distinguished:

  1. Sympathicotonic orthostatic hypotension: after standing up, systolic blood pressure drops while pulse increases.
  2. Asympathicotonic orthostatic hypotension: systolic and diastolic blood pressure sag when standing up, while the pulse remains unchanged or also drops.

Low blood pressure in pregnancy

During the first six months of pregnancy, low blood pressure is normal. However, sometimes it remains too low even in late pregnancy. The reason for this can be the so-called vena cava syndrome: This is when the unborn baby presses on the mother’s great vena cava.

This large blood vessel carries blood from the body back to the heart. The pressure of the child on the great vena cava therefore impairs the return flow of blood to the heart. As a result, the blood supply to the brain and other parts of the body is reduced – low blood pressure develops.

Low blood pressure: examinations and diagnosis

The tilt table test is performed especially on patients who have already fainted as a result of circulatory problems. During the test, the affected person is tied down on a tilt table with two restraining straps. Heart rate and blood pressure are monitored. After a ten-minute rest period in the lying position, the tilt table is quickly raised to a tilt angle of 60 to 80 degrees. This simulates standing up quickly from a lying position to see whether this causes blood pressure and pulse to drop and the patient to faint. If this is the case, it is called vasovagal syncope (fainting due to an excessive reaction of the vagus nerve, which belongs to the autonomic nervous system).

In contrast, low blood pressure as a result of inadequate orthostatic regulation (orthostatic hypotension) can be detected with the help of the Schellong test. In this circulatory test, the patient must first lie down for ten minutes and then quickly stand up and remain standing for ten minutes. In orthostatic hypotension, the rapid change in position causes a drop in blood pressure and possibly other symptoms (such as dizziness).