Blood pressure measurements provide two numbers: the systolic pressure, which is the higher number, and the diastolic pressure, which is the lower number. The systolic reading represents the pressure in the arteries when the heart contracts and pumps blood out. The diastolic reading indicates the pressure in the arteries when the heart rests between beats. While low blood pressure, or hypotension, may not always cause noticeable issues, a low diastolic reading can signal a reduction in blood flow that warrants attention. This condition, especially when persistent, can indicate underlying issues with heart function. Understanding the symptoms associated with a low diastolic pressure is important for knowing when to seek medical advice.
Defining Diastolic Pressure and Low Readings
Diastolic pressure measures the force exerted on artery walls during the period when the heart relaxes and refills with blood. This moment of rest is important because the heart muscle receives its oxygenated blood supply primarily during this diastolic phase. If this pressure is too low, the coronary arteries may not receive sufficient blood flow to nourish the heart muscle. A reading is typically classified as low diastolic pressure when the number consistently falls at or below 60 millimeters of mercury (mmHg) in adults. This measurement is sometimes referred to as isolated diastolic hypotension if the systolic number remains within a normal range. The concern with a reading below this 60 mmHg threshold is the potential for inadequate perfusion, meaning insufficient pressure exists to push blood into the organs, especially the heart tissue itself.
The Immediate and Common Symptoms
When the diastolic pressure drops too low, the immediate physical manifestations are often related to the brain not receiving enough blood flow, a condition known as cerebral hypoperfusion. A person may experience lightheadedness or dizziness, particularly when moving suddenly from a sitting or lying position to standing. This feeling can sometimes progress to blurred vision or even syncope (a brief loss of consciousness or fainting).
General systemic symptoms also frequently accompany low diastolic pressure, signaling a body-wide reduction in blood circulation. Unusual fatigue and a persistent lack of energy are common complaints, sometimes accompanied by a general feeling of weakness. Individuals may also report feelings of nausea or difficulty maintaining focus and concentration on tasks.
The body attempts to compensate for the low pressure by engaging the sympathetic nervous system, leading to specific physical signs. These compensatory mechanisms can result in a rapid, shallow breathing pattern as the body tries to increase oxygen supply. The skin may also appear pale and feel cool or clammy as blood flow is diverted away from the extremities and toward the core organs. Persistent and frequent occurrences of these signs should prompt consultation with a healthcare provider.
Underlying Causes
A variety of factors can lead to a low diastolic pressure reading, often by affecting the total volume of blood or the elasticity of the blood vessels.
Volume Depletion
One common category is volume depletion, which refers to a significant decrease in the body’s fluid content. This can occur due to dehydration from insufficient water intake, excessive sweating, or the loss of fluids from vomiting or severe diarrhea, all of which reduce the overall blood volume.
Medications
Certain prescription medications are also frequent causes of low diastolic pressure, particularly those used to manage high blood pressure. Diuretics, which increase urination, and certain alpha-blocker medications can lower the diastolic reading more significantly than the systolic reading. Other drug classes, including some used for Parkinson’s disease, depression, or erectile dysfunction, may also contribute to a drop in blood pressure.
Cardiovascular and Systemic Issues
Cardiovascular issues represent another category, as problems with the heart or arteries can directly impact pressure maintenance. Conditions like specific types of heart failure or issues with heart valves can impair the heart’s ability to fill or pump efficiently. As a person ages, the arteries naturally lose some of their elasticity, which can lead to a wider gap between the systolic and diastolic numbers. Severe systemic issues, such as a widespread infection (sepsis) or a severe allergic reaction, can cause blood vessels to widen dramatically, leading to a sudden, significant drop in pressure.
When Low Diastolic Pressure Becomes a Medical Emergency
While many symptoms of low diastolic pressure are manageable, certain signs indicate that the condition has progressed to a severe state requiring immediate medical intervention. These signs usually point toward the onset of shock, where organs are dangerously deprived of oxygen and nutrients. A sudden and complete loss of consciousness (syncope) is a clear signal for emergency assistance.
Other indicators of a severe pressure drop include a rapid yet weak pulse, reflecting the heart struggling to circulate blood volume effectively. The skin may become cold, clammy, and distinctly pale or bluish, reflecting poor circulation. Any sudden change in mental status, such as acute confusion or disorientation, suggests that the brain is critically starved of oxygen. The presence of chest pain, which may indicate insufficient blood flow to the heart muscle itself, is also a serious symptom. If these severe signs develop, emergency medical services should be contacted immediately.