Low blood pressure is generally considered to be a blood pressure reading below 90 millimeters of mercury (mm Hg) to the top number (systolic) or 60MillimeterHgto the bottom number (diastolic).
What is considered low blood pressure for one person may be good for another. Low blood pressure may not cause any noticeable symptoms, or it may cause dizziness and fainting. Sometimes low blood pressure can be fatal.
The causes of low blood pressure range from dehydration to serious illness. It's important to find out what's causing your low blood pressure so you can treat it if necessary.
Types of low blood pressure include:
- Orthostatic Hypotonia (Orthostatic Hypotonia).This is a sudden drop in blood pressure when getting up from a sitting position or after lying down. Causes include dehydration, prolonged bed rest, pregnancy, certain medical conditions, and some medications. This type of low blood pressure is common in older adults.
- Postprandial hypotension.This drop in blood pressure occurs 1 to 2 hours after eating. Older adults are more likely to be affected, particularly those with high blood pressure or autonomic nervous system disorders such as Parkinson's disease. Eating small, low-carb meals, drinking more water, and avoiding alcohol can help relieve symptoms.
- Neuromediated hypotension.This is a drop in blood pressure that occurs after standing for a long time. This type of low blood pressure mostly affects young adults and children. It could be the result of miscommunication between the heart and brain.
- Multiple system atrophy with orthostatic hypotension.Also known as Shy-Drager syndrome, this rare condition affects the nervous system, which controls involuntary functions such as blood pressure, heart rate, breathing, and digestion. It is associated with very high blood pressure when lying down.
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Symptoms of low blood pressure (hypotension) may include:
- Cloudy or blurred vision
- dizziness or lightheadedness
- concentration problems
For some people, low blood pressure can be a sign of an underlying health condition, especially if it drops suddenly or symptoms appear.
A sudden drop in blood pressure can be dangerous. A change of only 20MillimeterHg- a decrease of 110MillimeterHg90 systolicMillimeterHgsystolic, for example, can cause dizziness and fainting. And large droplets, such as those caused by uncontrollable bleeding, severe infection, or allergic reactions, can be deadly.
Extremely low blood pressure can lead to a condition known as shock. Shock symptoms include:
- Confusion, especially in the elderly.
- cold wet skin
- Decreased skin color (pallor)
- Rapid and shallow breathing
- Pulse weak and rapid
When to the doctor
If you have symptoms of extremely low blood pressure (hypotension) or shock, seek emergency medical attention.
Most health professionals only consider blood pressure too low if it's causing symptoms. Occasional mild dizziness or dizziness can be caused by many things, including spending too much time in the sun or in a hot tub. It is important to see a doctor to get a proper diagnosis.
If you have persistently low blood pressure but feel well, your doctor may monitor you during routine wellness check-ups. It can be helpful to document your symptoms, when they occur, and what you are doing.
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Blood pressure is determined by the amount of blood that the heart pumps and the resistance to blood flow in the arteries. Blood pressure is measured in millimeters of mercury (mm Hg). It has two numbers:
- systolic pressure.The first (top) number is the pressure in the arteries when the heart is beating.
- diastolic pressure.The second number (below) is the pressure in the arteries when the heart is resting between beats.
The American Heart Association classifies ideal blood pressure as normal. An ideal blood pressure is usually below 120/80MillimeterHg.
Blood pressure varies throughout the day depending on:
- body position
- to eat and drink
- Physical condition
Blood pressure is usually lowest at night and rises sharply when you wake up. Certain health conditions and taking medications can lead to low blood pressure.
Conditions that can lead to low blood pressure
Medical conditions that can lead to low blood pressure include:
- The pregnancy.Changes during pregnancy cause blood vessels to dilate rapidly. The changes can cause your blood pressure to drop. Low blood pressure is common in the first 24 weeks of pregnancy. Blood pressure usually returns to pre-pregnancy levels after childbirth.
- Diseases of the heart and heart valves.A heart attack, heart failure, heart valve disease, and an extremely slow heart rate (bradycardia) can lead to low blood pressure.
- Hormone-related diseases (endocrine disorders).Conditions affecting the parathyroid or adrenal glands, such as Addison's disease, can lead to a drop in blood pressure. Low blood sugar (hypoglycemia) and sometimes diabetes can lower blood pressure.
- dehydration.When the body does not have enough water, the amount of blood in the body (blood volume) decreases. This can cause your blood pressure to drop. Fever, vomiting, severe diarrhea, overuse of diuretics, and strenuous exercise can lead to dehydration.
- blood lossLosing too much blood, such as from injury or internal bleeding, also decreases blood volume, causing a sharp drop in blood pressure.
- Severe infection (sepsis).When an infection in the body enters the bloodstream, it can cause a life-threatening drop in blood pressure called septic shock.
- Severe allergic reaction (anaphylaxis).Symptoms of a severe allergic reaction include a sudden, drastic drop in blood pressure.
- Lack of nutrients in the diet.Low levels of vitamin B-12, folic acid, and iron can prevent the body from making enough red blood cells (anemia), which can lead to low blood pressure.
Medicines that can lead to low blood pressure
Some medications can cause low blood pressure, including:
- Water pills (diuretics) such as furosemide (Lasix) and hydrochlorothiazide (Microzide)
- Alpha blockers such as Prazosin (Minipress)
- Beta blockers such as atenolol (Tenormin) and propranolol (Inderal, Innopran XL, Hemangeol)
- Medicines for Parkinson's disease, such as pramipexole (Mirapex) or those containing levodopa
- Certain types of antidepressants (tricyclic antidepressants), including doxepin (Silenor) and imipramine (Tofranil)
- Medications for erectile dysfunction, including sildenafil (Revatio, Viagra) or tadalafil (Adcirca, Alyq, Cialis), especially when taken with the heart drug nitroglycerin (Nitrostat, Nitro-Dur, Nitromist).
Anyone can have low blood pressure (hypotension). Risk factors for hypotension include:
- Years.A drop in blood pressure when standing up or after eating is most common in adults over the age of 65. Hypotension of neuronal origin mainly affects children and young adults.
- medicationCertain medications, including some blood pressure medications, increase your risk of low blood pressure.
- Certain diseases.Parkinson's disease, diabetes and some heart conditions can increase your risk of low blood pressure.
Possible complications of low blood pressure (hypotension) include:
- fall injuries
Very low blood pressure can reduce the amount of oxygen in the body, which can damage the heart and brain.
By the staff of the Mayo Clinic