Low Blood Pressure
Low blood pressure, also called hypotension, happens when blood pressure falls below what is considered normal — a reading of 90/60 or lower. When blood pressure is much lower than normal, it means not enough blood is flowing to the heart, brain and other parts of the body.
Some people may naturally have low blood pressure all the time with no symptoms. Their low readings are normal for them. But for others, their blood pressure may drop for a variety of reasons ranging from a medical condition to dehydration.
Low blood pressure is only a problem if a person develops symptoms, which can include dizziness, fainting or shock. In severe cases, it can be life-threatening. But low blood pressure without these serious symptoms is usually not unhealthy.
Low blood pressure that reduces the blood supply to your body’s organs can cause stroke, kidney failure or heart attack.
Understanding how to treat and prevent low blood pressure is important for your cardiovascular health.
Understanding Blood Pressure
Blood pressure is the force of blood pressing against arteries as the heart pumps it through the body. The pressure is highest when your heart beats, pumping the blood. It’s lowest between beats, when the heart rests.
Blood pressure is measured by comparing these two numbers, placing one over the other. The high measurement is called the systolic pressure, and it is placed on the top of the reading. The lower pressure is called the diastolic pressure, and it’s written as the bottom number.
Ideally, your blood pressure should be 120 over 80 — written as 120/80 — or lower. Low blood pressure is anything lower than 90/60.
What Causes Low Blood Pressure?
Causes of low blood pressure are wide-ranging and can include changes in your body’s functions, environmental causes, and trauma or a serious medical condition.
- Anaphylactic shock
- Endocrine conditions such as Addison’s disease, hypothyroidism, parathyroid disease, low blood sugar and diabetes
- Heart conditions such as heart attack, heart failure, low heart rate and heart valve issues
- Long-term bed rest
- Nutritional deficiencies such as low folic acid or vitamin B12 levels, which can lead to anemia
- Pregnancy, especially in the first 24 weeks
- Septic shock
- Sudden loss of blood volume such as from an accident, dehydration or internal bleeding
Source: American Heart Association
Age, medications and medical conditions are all risk factors for low blood pressure.
People with Parkinson’s disease, diabetes and certain heart conditions are at greater risk. Those 65 and older are more likely to experience a sudden blood pressure drop when standing or right after eating.
Medications that Can Cause Low Blood Pressure
Several medicines may cause low blood pressure, including some medications used to control high blood pressure.
Working with your doctor or other health care provider to change your medication or adjust your dosage can help control low blood pressure. You should never modify a dose or stop taking a medication without first consulting your health care provider.
Alpha and beta blockers, diuretics, erectile dysfunction drugs, Parkinson’s disease drugs and some types of antidepressants can cause low blood pressure.
- Benicar (olmesartan medoxomil) — a prescription blood pressure medication
- Cialis (tadalafil) — an erectile dysfunction drug; risk is especially high when taken with nitroglycerin heart medication
- Cymbalta (duloxetine) — a serotonin and norepinephrine inhibitor (SNRI) antidepressant
- Hydrochlorothiazide — a widely used generic diuretic
- Inderal, Innopran XL and other versions of propranolol — beta blockers
- Lasix (furosemide) — a diuretic
- Levodopa — a generic name for Parkinson’s disease drugs
- Minipress (prazosin) and other alpha blockers
- Mirapex (pramipexole) — a Parkinson’s disease drug
- Tenormin (atenolol) — an alpha blocker
- Tricyclic antidepressants — includes Silenor (doxepin) and Trofranil (imipramine)
- Valsartan and other blood pressure drugs in the sartan family
- Viagra (sildenafil) — an erectile dysfunction drug; risk is especially high when taken with nitroglycerin heart medication
In most cases, you shouldn’t worry about a low blood pressure reading unless you have symptoms of a serious or underlying problem.
- Blurred vision
- Lack of concentration
- Lightheadedness or dizziness
Severe or extreme low blood pressure can be life-threatening. This can happen if your body goes into shock from blood loss, an anaphylactic reaction or septic shock from a serious infection.
- Rapid but weak pulse
- Rapid shallow breathing
- Pale, cold, clammy skin
- Confusion (especially in older people)
What to Do if You Experience a Sudden Drop in Blood Pressure
A single low blood pressure reading is no cause to be concerned unless you experience other symptoms.
A sudden drop in blood pressure — as little as a drop from 120 to 100 in your systolic (top) number — can be dangerous if it triggers dizziness and fainting. Such symptoms can be a sign of an underlying problem that may need medical attention.
You should keep a record of your activities and when symptoms happen to discuss them with your doctor. If you experience any low blood pressure symptoms related to shock, you should seek immediate medical attention.
Types of Low Blood Pressure
There are three major types of low blood pressure: orthostatic hypotension, postprandial hypotension and neurally mediated hypotension. Each is triggered by something different such as a change in body position, a meal or an abnormal reflex.
Orthostatic hypertension is low blood pressure caused by a change in your body’s position that most often happens when you stand up after lying down. It lasts only a few seconds or minutes.
Orthostatic low blood pressure is caused by gravity as your blood pools in your legs. Your heart would normally compensate, pumping more blood to your brain. But with this type of low blood pressure, that mechanism fails, your brain gets less oxygen from the bloodstream and you may feel lightheaded or dizzy. In some cases, you may faint.
It most often affects older people, people with high blood pressure and those with Parkinson’s disease. But you may also experience it if you are pregnant, dehydrated, overheated, or have heart problems, diabetes or certain nerve disorders.
Postprandial hypotension is a sudden drop in blood pressure after eating.
Usually after a meal, your heart rate ramps up to send blood flowing to your digestive system. But with this type of low blood pressure, the mechanism fails causing dizziness and fainting. It can also cause people to fall and possibly injure themselves.
Eating small meals that are low in carbohydrates can sometimes reduce symptoms.
Neurally Mediated Hypotension
Neurally mediated hypotension happens when there is an abnormal reflex between a person’s otherwise normally functioning heart and brain, according to Johns Hopkins Hospital. It’s sometimes called the fainting reflex.
People with this type of low blood pressure may feel lightheaded or dizzy or may faint. Other symptoms may include chronic fatigue, muscle aches, headaches and confusion.
Symptoms may happen after being in warm surroundings such as a hot shower or bath or hot summer weather. Other triggers include standing quietly for a long period of time, such as a service member at attention. It can happen after exercise, after eating or following emotionally stressful situations.
With this type of low blood pressure, gravity allows blood to pool in the legs. The heart needs to beat faster to supply the brain with enough blood, but a malfunction causes the brain to tell the heart to beat less, decreasing the blood supply to the brain.
Low blood pressure seldom requires treatment, unless it’s the result of sudden trauma, infection, anaphylactic shock or other serious underlying cause.
If it’s caused by medications, your doctor may prescribe a different medication or simply alter your dosage.
- Wear compression stockings to prevent the pooling of blood in the legs
- Drink fluids to prevent or relieve dehydration, a major cause of common low blood pressure
- Eat more salt to raise blood pressure
Your doctor may prescribe Orvaten (midodrine) to raise your blood pressure if you are diagnosed with chronic orthostatic hypotension. For milder forms, a doctor may prescribe fludrocortisone to boost your blood volume. There are several other drugs that may be available depending on your particular type and severity of low blood pressure.
Please seek the advice of a medical professional before making health care decisions.