What is Low Blood Pressure?
Dr. Angel Rivera
We often hear about the dangers of high blood pressure, but is it possible for your blood pressure to be too low? With high blood pressure such a concern, it might stand to reason that the lower your blood pressure is, the better. While this can be true for people who are otherwise healthy without any health conditions, low blood pressure can cause bothersome and sometimes dangerous symptoms and can be a sign of an underlying medical condition.
What is low blood pressure?
We all have blood pressure - it’s an essential force that helps keep us alive. Blood pressure is the force, or blood flow, at which your blood pushes against the walls of your blood vessels, like your arteries, veins, and capillaries. Our bodies, including all of our tissues and organs, function using the oxygen they receive from our blood. Our heartbeat is the mechanism by which blood is pushed out of the heart and through the blood vessels. Each time our heart beats, blood is sent through the body to the organs and extremities, delivering vital oxygen.
Blood pressure is measured using two different readings that measure blood pressure at different times: systolic pressure and diastolic pressure. Systolic pressure is measured as the blood pumps out of the heart and into the arteries and can be considered a measurement of “active” blood pressure. The systolic pressure will be the first or top number listed on a blood pressure reading. The second, or bottom, number of a blood pressure reading is the diastolic pressure. This number is taken as your heart rests between beats, measuring the blood pressure in your blood vessels when the heart is not actively working. Diastolic pressure may be thought of as the “resting” pressure.
Lower blood pressure, or hypotension, is a medical condition characterized by a consistently lower than normal flow of blood to the tissues, organs, and extremities. In people who are otherwise healthy, and have no symptoms, low blood pressure is generally not a cause for concern. After all, there is so much talk about the dangers of high blood pressure that it seems like having low blood pressure would be ideal. However, low blood pressure can sometimes be a sign of an underlying medical problem, especially in people over the age of 65. Dizziness or lightheadedness can occur when the brain is left without an adequate blood supply.
What are the two types of low blood pressure?
There are two types of low blood pressure. The first type, known as postural hypotension or orthostatic hypotension, happens when a sudden drop in blood pressure occurs due to a person changing positions quickly, such as moving from a sitting position to standing. The second type of low blood pressure, called neurally mediated hypotension, happens when someone stands for a long period of time.
What causes low blood pressure?
Postural hypotension is most commonly caused by dehydration, blood loss or loss of blood, anemia, and certain medications. These factors can cause your body to respond too slowly to changes in movement. As you move from sitting to standing or from lying down to sitting, your body should correct for blood pooling in the extremities by sending your heart a message to beat faster and for your blood vessels to constrict. When your body is unable to respond to these messages quickly enough, postural hypotension occurs, which can sometimes cause fainting. Postural hypotension is most commonly experienced by people taking medications to control high blood pressure, but it can also be associated with the following conditions and side effects:
- Electrolyte loss
- Old age
- Hormonal issues such as hypothyroidism, diabetes, or low blood sugar (hypoglycemia)
- Strong emotions
- Erectile dysfunction
- Hardening of the arteries (atherosclerosis)
- Eating a high carb meal
- Parkinson's Disease
- Taking blood pressure medications, such as beta blockers
- Taking nitrates, anti-psychotics, anti-anxiety agents, sedatives, and antidepressants
Neurally mediated hypotension, on the other hand, is caused by a chance in the activity of the autonomic nervous system, and it often results in fainting. A drop or pause in heart rate can also occur. Neurally mediated hypotension occurs when there is a mixup in the signals between the heart and the brain. When the heart should be triggered to beat faster to make up for blood pooling in the extremities after standing for a long period of time, it receives an incorrect message from the brain telling it to slow down and narrow the blood vessels instead. This results in a drop in blood pressure and can cause lightheadedness or fainting due to a lack of blood reaching the brain.
What are the blood pressure measurement ranges?
There are five different categories for blood pressure. Blood pressure readings are written by the American Heart Association by placing the systolic, or “active,” number on top and the diastolic, or “resting,” number on the bottom.
- Low blood pressure: Less than 90 over less than 60 (Less than 90/less than 60)
- Normal blood pressure: 90 - 120 over 60 - 80 (90-120/60-80)
- Elevated: 120 - 129 over less than 80 (120-129/less than 80)
- Stage 1 high blood pressure: 130-139 over 80 - 89 (130-139/80-89)
- Stage 2 high blood pressure: 140 and above over 90 and above (140 and above/90 and above)
- Hypertension crisis: higher than 180 over higher than 120 (higher than 180/higher than 120). In cases of a hypertension crisis, seek medical attention right away.
What are the symptoms associated with low blood pressure?
Low blood pressure may not cause any symptoms. When this is the case, it’s generally ok for your blood pressure to be low. If low blood pressure does causes symptoms, they may include:
- Dizziness or lightheadedness
- Lack of concentration
- Blurred vision
- Cold, clammy, pale skin
- Rapid, shallow breathing
How can I prevent low blood pressure?
If your low blood pressure is causing you to experience unwanted symptoms like fainting and dizziness, there are steps you can take to treat and prevent it. These include:
- Identify the cause: The first step to preventing enough blood pressure drops is to attempt to identify the issue that is causing it. Low blood pressure is frequently caused by medication, so ask your doctor or medical advice professional or pharmacist to review a list of any prescription or over-the-counter medications you may be taking.
- Increase your fluid intake: Low blood pressure can be caused by dehydration. Increase your fluid intake if it is safe to do so (i.e. you have no other medical conditions, like heart failure, heart attack or kidney disease, that could be made worse by drinking more water). Make sure to drink extra water before engaging in activities that could be strenuous, such as shopping, exercising, or household chores.
- Ask about adding salt: Some people experience low blood pressure because their sodium intake is not high enough. Adding salt to your diet can cause other issues, so talk to your diet about your medical history to see if increasing your sodium intake can help your low blood pressure.
- Eat small meals frequently: Sudden drops in blood pressure can be caused by eating large, carbohydrate-rich meals. Eat smaller meals at regular intervals throughout the day, and keep carb-heavy meals for later in the day when you will be able to lie down after eating.
- Stay fit: Blood pressure and heart problems go hand and hand. Make sure to get enough exercise and stay fit to keep your heart strong. Exercise helps improve your circulation.
- Avoid triggers: Situations like standing for a long period of time, getting up too quickly, spending lots of time in the heat, and drinking too much alcohol can trigger low blood pressure. Try to avoid these situations if possible or consider wearing compression stockings.
- Sleep in a reclined position: Keeping your head elevated above your heart may help minimize low blood pressure upon waking or if you're on bed rest. Either elevate your head by supporting the top of your bed with blocks, or sleep in a recliner. Foam pillows are also sold for this purpose.
- Move slowly in the morning: The symptoms of low blood pressure are often worst in the morning after a long period of lying down, so move with caution in the morning. Drink water before getting out of bed and get out of bed as slowly as possible.
- Manage your weight: People who are underweight are more likely to have low blood pressure than those of normal weight. If you need to gain weight, talk to your doctor about how to do so in a healthy manner.
- Take medication if needed: People with chronically low blood pressure or very low blood pressure may need to take medication to keep their blood pressure at a level that is safe. Examples of medications used to treat low blood pressure include fludrocortisone, desmopressin, midodrine, pyridostigmine, and octreotide.
When should I be concerned about low blood pressure?
You should be concerned about low blood pressure if it causes bothersome symptoms on a regular basis or if you experience a sudden drop in blood pressure. A sudden drop in blood pressure can be life-threatening, so you should consult your doctor immediately. Causes of low blood pressure or sudden drops in blood pressure can be caused by:
- Excessively high body temperature (hyperthermia)
- Excessively low body temperature (hypothermia)
- Loss of blood from bleeding
- Heart disease causing heart failure
- Severe infection
- Severe dehydration
- A reaction to medication or alcohol
- A severe allergic reaction (anaphylaxis) that causes an irregular heartbeat