Low blood pressure (hypotension) – Symptoms and causes – Mayo Clinic

summary

Low blood pressure is generally considered a blood pressure reading less than 90 millimeters of mercury (mm Hg) for the top number (systolic) or 60 mm Hg for the bottom number (diastolic).

What is considered low blood pressure for one person may be fine for another. low blood pressure may cause no noticeable symptoms or may cause dizziness and fainting. sometimes low blood pressure can be life-threatening.

Causes of low blood pressure range from dehydration to serious medical conditions. It’s important to find out what’s causing your low blood pressure so you can treat it, if needed.

types

Types of low blood pressure include:

• Orthostatic hypotension (postural hypotension). This is a sudden drop in blood pressure when standing 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. it is more likely to affect older adults, especially those with high blood pressure or diseases of the autonomic nervous system, such as Parkinson’s disease. eating small, low-carb meals, drinking more water, and avoiding alcohol may help reduce symptoms.
• nerve-mediated hypotension. This is a drop in blood pressure that occurs after standing for long periods. This type of low blood pressure primarily affects young adults and children. it could be due to a miscommunication between the heart and the brain.
• multiple system atrophy with orthostatic hypotension. also called shy-drager syndrome, this rare disorder affects the nervous system that controls involuntary functions such as blood pressure, heart rate, breathing, and digestion . is associated with having very high blood pressure while lying down.

symptoms

Symptoms of low blood pressure (hypotension) may include:

• blurred or dim vision
• dizziness or lightheadedness
• fainted
• fatigue
• trouble concentrating
• nausea

For some people, low blood pressure can be a sign of an underlying health condition, especially when it drops suddenly or presents with symptoms.

A sudden drop in blood pressure can be dangerous. a change of just 20 mm Hg, a drop from 110 mm Hg systolic to 90 mm Hg systolic, for example, can cause dizziness and fainting. and large droplets, such as those caused by uncontrollable bleeding, serious infections, or allergic reactions, can be life-threatening.

Extremely low blood pressure can lead to a condition known as shock. symptoms of shock include:

• confusion, especially in older people
• cold and clammy skin
• decreased skin color (pallor)
• rapid, shallow breathing
• rapid weak pulse

when to see a doctor

If you have symptoms of extremely low blood pressure (hypotension) or shock, seek emergency medical help.

Most health care providers consider blood pressure to be too low only if it causes symptoms. Occasional minor dizziness or lightheadedness can be caused by many things, such as spending too much time in the sun or in a hot tub. it is important to see a health care provider to get a correct diagnosis.

If you have consistently low blood pressure readings but feel fine, your provider may monitor you during routine health checkups. It can be helpful to keep track of your symptoms, when they occur, and what you’re doing at the time.

causes

Blood pressure is determined by the amount of blood pumped by the heart and the amount of resistance to blood flow in the arteries. A measurement of blood pressure is given in millimeters of mercury (mm Hg). has two numbers:

• systolic pressure. the first (top) number is the pressure in the arteries when the heart beats.
• diastolic pressure. the second (bottom) number is the pressure in the arteries when the heart rests between beats.

The American Heart Association classifies ideal blood pressure as normal. an ideal blood pressure is usually less than 120/80 mm Hg.

Blood pressure varies throughout the day, depending on:

• body position
• breathing
• food and drink
• medications
• physical condition
• stress
• time of day

Blood pressure is usually lower at night and rises sharply on waking. certain health conditions and the use of medications can cause low blood pressure.

conditions that can cause low blood pressure

Medical conditions that can cause low blood pressure include:

• pregnancy. Changes during pregnancy cause blood vessels to expand rapidly. changes can cause 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 delivery.
• heart and heart valve conditions. Heart attack, heart failure, heart valve disease, and extremely slow heart rate (bradycardia) can cause low blood pressure.
• hormone-related diseases (endocrine disorders). conditions that affect the parathyroid or adrenal glands, such as addison’s disease, can cause a drop in blood pressure. Low blood sugar (hypoglycemia) and sometimes diabetes can also 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 blood pressure to drop. fever, vomiting, severe diarrhea, overuse of diuretics, and strenuous exercise can cause dehydration.
• blood loss. Loss of a lot of blood, such as from an injury or internal bleeding, also reduces blood volume, causing a serious drop in blood pressure.
• serious infection (sepsis). When an infection in the body enters the bloodstream, it can cause a life-threatening drop in blood pressure called septic shock.
• Serious allergic reaction (anaphylaxis). Symptoms of a severe allergic reaction include a sudden and 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 .

medications that can cause 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)
• medications for Parkinson’s disease, such as pramipexole (mirapex) or those containing levodopa
• certain types of antidepressants (tricyclic antidepressants), including doxepin (silenor) and imipramine (tofranil)
• Erectile dysfunction medications, including sildenafil (Revatio, Viagra) or tadalafil (Adcirca, Alyq, Cialis), especially when taken with the heart medication nitroglycerin (Nitrostat, Nitro-dur, Nitromist)

risk factors

Anyone can have low blood pressure (hypotension). risk factors for hypotension include:

• age. Drops in blood pressure when standing up or after eating occur mainly in adults older than 65 years. neurally mediated hypotension primarily affects children and young adults.
• Medications. Certain medications, including some blood pressure medications, increase the risk of low blood pressure.
• Certain diseases. Parkinson’s disease, diabetes, and some heart conditions can increase the risk of low blood pressure.

complications

Possible complications of low blood pressure (hypotension) include:

• dizziness
• weakness
• fainted
• fall injuries

Very low blood pressure can reduce the body’s oxygen levels, which can lead to heart and brain damage.