Why is My Blood Pressure Suddenly High and Low?

Medically Reviewed on 7/6/2022

What is high blood pressure?

Blood pressure can be defined as the force your blood creates when it's flowing through your arteries. Blood pressure may be high or low due to medication side effects, certain medical conditions, or unknown reasons.
Blood pressure can be defined as the force your blood creates when it's flowing through your arteries. Blood pressure may be high or low due to medication side effects, certain medical conditions, or unknown reasons.

Blood pressure can be defined as the force your blood creates when it’s flowing through your arteries (the blood vessels that transport blood from the heart to other body parts). This pressure comes from your blood pushing through the arteries when your heart pumps it.

High blood pressure, or hypertension, is when your blood travels through your arteries at a pressure that's higher than normal. Having hypertension can cause some serious health issues if not controlled or managed in time. High blood pressure can expose you to a higher risk of getting conditions like heart attack, heart disease, kidney failure, and stroke.

High blood pressure has two classifications:

  1. Primary hypertension (essential hypertension). This is the most common type of high blood pressure. Mostly the exact cause is unknown, but it’s usually associated with lifestyle, aging, family history, or the environment. It develops slowly for years before appearing.
  2. Secondary hypertension. This type of hypertension is usually caused by factors like medications or underlying medical issues.

Main symptoms of high blood pressure

Usually, high blood pressure will rarely cause any obvious symptoms. Sometimes you may see symptoms when it becomes severe. Some of those symptoms include:

Main causes of high blood pressure

Some factors may make you more likely to get high blood pressure. They include:

  • Aging (over 65)
  • Smoking
  • Excess weight gain
  • Lack of physical exercise
  • Lack of enough sleep
  • Eating excess salt
  • Excessive drinking
  • Close relatives with high blood pressure
  • Excessive caffeine intake (coffee and other foods)

In some cases, high blood pressure is caused by some medications or other serious underlying health conditions. If you get high blood pressure due to medications, discontinuing them may get your blood pressure back to normal. 

Health conditions that are commonly known to cause hypertension are:

  • Diabetes
  • Narrowing of arteries of the kidneys
  • Glomerulonephritis 
  • Kidney disease and infections
  • Hormonal issues
  • Lupus (a condition that causes the immune system to attack the body)
  • Scleroderma (an illness that leads to skin thickening and issues with blood vessels or other organs)
  • Obstructive sleep apnea (narrowing of the throat during sleep)

Medications that may cause increased blood pressure are:

Treatment of high blood pressure

Treatment of high blood pressure may involve managing the underlying condition. For example, if the hypertension is due to kidney disease or hormone issues, treating these conditions may help to bring your blood pressure back to normal.

Your doctor may also recommend that you make some lifestyle changes like:

  • Eating a healthy, balanced diet (including fruits, vegetables, low-fat dairy, and low salt content)
  • Getting regular physical exercise
  • Quitting smoking
  • Avoiding alcohol
  • Avoiding caffeine (in tea, sodas, coffee, and energy drinks)

What is low blood pressure?

Low blood pressure (hypotension) occurs when blood travels through your arteries at a lower pressure than normal. Low blood pressure occurs normally in some people and it may happen almost all the time. This usually happens without a specific cause. But it can be due to genetic inheritance, being active or fit, or living a healthy lifestyle. 

However, sometimes it may be linked to an underlying health issue. This type of low blood pressure is dangerous because it may be an indication of a blood flow issue in the brain, heart, or other vital organs. Low blood pressure may also put you at risk of getting a stroke or a heart attack.

Main symptoms of low blood pressure

Just like high blood pressure, low blood pressure rarely causes obvious symptoms. Many people who have it don’t even notice it. Some people may get:

Main causes of low blood pressure

As mentioned earlier, low blood pressure might be a sign of an underlying condition. Common causes of low blood pressure include:

  • Dehydration
  • Pregnancy
  • Diabetes
  • Blood donation
  • Addison’s disease
  • Emotional stress (due to pain, fear, or insecurity)
  • Nervous system disorders like Parkinson’s disease
  • Extreme heat (the body causes a drop in blood pressure to manage heat)
  • Diuretics (they cause body fluid loss)
  • Allergic reactions to some drugs and chemicals
  • Infections like toxic shock syndrome
  • Excess blood loss after an injury
  • Heart issues like an irregular heartbeat (arrhythmias)
  • Depression medications
  • High blood pressure medications

Postural or orthostatic hypotension. This is a type of low blood pressure that occurs when you make posture changes, like going from a sitting or lying position to standing up. While doing so, your blood pressure may drop, causing you to get some low blood pressure symptoms like dizziness or fainting. However, this type of low blood pressure does not last for long since your body adjusts to the new posture.

Orthostatic hypotension may be caused by:

  • Dehydration
  • Irregular heartbeat
  • Prolonged bed rest
  • Nervous system conditions (like neuropathy)


How to Lower Blood Pressure: Exercise and Tips See Slideshow

Treatment of low blood pressure

Treatment of low blood pressure depends on the cause of the condition. For instance, if your hypotension is due to medications you are taking, treatment will involve changing or discontinuing the dosage of the medication. If it’s due to an underlying condition, like a bleeding stomach ulcer, management of hypotension will involve treating the ulcer through surgery.

Diagnosing high and low blood pressure

If you are 40 years and above, you should consider getting your blood pressure tested at least once in five years. You can get your blood pressure checked by your doctor or at home using a blood pressure monitor. One blood pressure test can’t determine conclusively if you have an issue with your blood pressure.

Your blood pressure can change due to factors like stress or anxiety. Because of this, your doctor may do a couple of tests within 24 hours (ambulatory monitoring) or over a longer period. Doing so helps to determine whether your blood pressure issue is consistent.

Medically Reviewed on 7/6/2022

American Academy of Family Physicians: "High Blood Pressure."

BetterHealth: "Blood pressure (low) - hypotension."

Blood Pressure Association: "What is low blood pressure?"

KidsHealth: "Hypertension (High Blood Pressure)."

National Heart, Lung, and Blood Institute: "LOW BLOOD PRESSURE."

NHS: "Diagnosis-High blood pressure (hypertension)," "Causes-High blood pressure(hypertension)."