Check all that occur as a result of low blood volume and low blood pressure.

What causes low blood pressure and what are low blood pressure symptoms?

I suffer from low blood pressure, which means I often feel dizzy. What causes this and what are the treatments?

Dr Paolo Tammaro says:

High blood pressure (hypertension) is a major medical concern. If untreated, it can lead to heart attacks, strokes, kidney damage and even premature death. Low blood pressure might therefore seem desirable. However, excessively low blood pressure (hypotension) can cause various problems. 

What is low blood pressure? 

Blood pressure is the pressure of blood in your arteries - the vessels that carry your blood from your heart to your brain and the rest of your body. You need a certain amount of pressure to get the blood round your body. 

A normal blood pressure is less than 140/90mmHg (a desirable blood pressure is around 120/80mmHg). Low blood pressure is a measurement of 90/60mmHg or lower. 

When your blood pressure drops, your heart rate increases and the blood vessels in other parts of the body constrict (narrow) to help maintain blood pressure. If your heart rate does not increase enough, or if your blood vessels do not constrict enough to maintain blood pressure, your blood pressure will fall. 

The kidneys control blood volume, so are also involved in regulating blood pressure. 

• Find out more about high and low blood pressure.

Symptoms of low blood pressure (hypotension): 

• Light-headedness or dizziness 
• Fainting 
• Blurred vision 
• Weakness 
• Difficulties in concentration or confusion 
• Nausea (feeling sick) 

Causes of low blood pressure 

• Standing up: it may occur when you stand up (postural hypotension) 
• After eating, when blood flow to your digestive system increases (this is most likely to occur if you have a disease of the nervous system, such as Parkinson's). 
• Some medical conditions (mainly endocrine and neurological disorders and some cardiac conditions such as heart failure and arrhythmias.) 
• Medical emergencies: some emergencies such as septic shock and anaphylactic shock will also cause dangerously low blood pressure. 
• Side effects from certain medications (for high blood pressure, heart disease or depression) and from some over-the-counter and herbal medicines 
• Blood loss and dehydration 

Treatments for low blood pressure 

Medication for low blood pressure is rarely needed. This is because making simply lifestyle changes or treating the underlying cause is usually effective. Drinking more fluids, raising your legs and changing or altering the dose of medication you are taking are all effective ways of easily treating low blood pressure. 

However, if it causes issues, low blood pressure can be treated with different medicines, depending on the underlying cause.  

1. Beta-agonists or alpha-agonists: Beta-agonists make the heart beat faster, while alpha-agonists narrow the blood vessels. 
2. Fludrocortisone: Drugs such as fludrocortisone, (a steroid that makes your kidneys retain water and salt, increasing your blood volume), can also be used.  

Research into low blood pressure  

Not all patients respond well to these treatments or tolerate the side effects – pharmacologists and other scientists are looking for new drugs. 

With the help of BHF funding, my lab is studying how to use drugs to control the width of arteries and therefore blood pressure. 

In particular, we are looking at the tiny channels in the artery wall that allow charged ions to go in and out of the artery cells, causing small electrical impulses.  Drugs acting on these channels have the potential to control the width of arteries and could offer new ways to control low and high blood pressure. 

Learn more about your blood pressure 

• Find out how to choose a blood pressure monitor and measure your blood pressure at home.
• Read more on how low your blood pressure should be.

Meet the expert

Dr Paolo Tammaro is Associate Professor in Pharmacology at the University of Oxford. His BHF-funded research is looking for potential new drugs to control blood pressure function that could help with both high and low blood pressure.