Blood pressure: how low can you go?

Low blood pressure isn't usually something to worry about unless you’re experiencing serious symptoms. Find out when you need to seek medical help.

Blood pressure (BP) is the force of blood pushing against the walls of your arteries, which carry blood from your heart to the rest of your body. Hypotension (low blood pressure) is when your BP reading is lower than 90/60 mm Hg. For most adults, normal blood pressure is less than 120/80 mm Hg.

Some healthy people may naturally have low blood pressure, but it's not usually a problem unless they experience serious symptoms.

“If the patient is not in a hospital setting, we advise people with low blood pressure to take in a lot of fluids and salt, which helps to raise their blood pressure,” says Dr Madimetja Mushi, a physician at Mediclinic Highveld.

What can cause low blood pressure?

Blood loss: One cause of hypotension is having less blood in your body, which can happen if you bleed a lot. This could be from things like cutting an artery or vein, or from bleeding in your stomach or intestines, such as with a stomach ulcer.

Fluid loss: “The loss of other body fluids can also lead to hypotension – for example, through diarrhoea or vomiting. People with undiagnosed diabetes (both type 1 and type 2) might have low blood pressure because they lose too much water from urinating often. Excessive sweating can also lead to low blood pressure,” Dr Mushi says.

Pregnancy: Blood vessel dilation can cause a temporary drop in blood pressure. As the uterus grows, it can compress major blood vessels, like the inferior vena cava, which returns blood from the lower body to the heart. This compression can reduce blood flow and contribute to lower blood pressure, particularly when lying on the back.  

Infections: Infections like septicaemia can cause low blood pressure, especially infections from bacteria like E. coli. Viral, fungal, or parasitic infections may lead to septicaemia, which can cause organs to stop working and may lead to septic shock. If not treated, this can be deadly.

Allergic reactions: Severe allergic reactions, like anaphylactic shock from a bee sting or food allergy, can also cause low blood pressure. If the allergic reaction isn’t treated urgently, it can lead to life-threatening anaphylactic shock.

Heart problems: Low blood pressure can also be caused by heart problems,. Conditions like ischaemic heart disease that leads to acute myocardial infarction (heart attack), heart failure, arrhythmias (abnormal heart rhythms), and heart valve disease can affect the heart's ability to pump blood effectively. When the heart isn't able to pump properly, it can cause blood pressure to drop, explains Dr Mushi.

Nerve diseases: Low blood pressure can also be caused by nerve problems, like autonomic dysfunction (which affects how your body controls blood pressure), and diseases such as Parkinson’s.

Post-prandial orthostatic hypotension: This condition occurs when your blood pressure drops a lot after eating. It is more likely to occur in older adults. “Post prandial hypotension happens when the stomach and oesophagus expand after eating, which causes blood vessels in the digestive area to widen,” explains Dr Mushi. “This leads to lower blood pressure and can make you feel tired after a meal."

He advises people with this condition not to stand up too quickly after eating or getting out of bed.

Autoimmune diseases: Other causes of low blood pressure include autoimmune diseases, like systemic lupus, arthritis, and Sjogren’s syndrome.

Medications: Certain medicines may trigger low blood pressure. This includes high doses of blood pressure medicines, diuretics, anti-anxiety drugs, and painkillers given through an IV, like paracetamol.

“Doctors can’t always find the cause of hypotension and it may be genetic,” says Dr Mushi. “Although it is rare, some people are also just born with low blood pressure and there is no secondary cause.”

What happens when hypotension is left untreated?

Most people with low blood pressure do not need any medical treatment. However, if there is a medical cause for the low blood pressure and it is not treated, this can lead to other problems.

“Low blood pressure means there isn't enough pressure in your blood vessels, which can affect the flow of blood to your organs. This can cause problems like low urine output, shortness of breath, confusion, and an irregular heartbeat.,” says Dr Mushi.

Other symptoms can include dizziness, fainting, feeling light-headed, tiredness, blurry vision, and general weakness – all due to poor blood flow to the organs.

Treatment for hypotension

“Normally, we just need to investigate and treat the cause of low blood pressure,” says Dr Mushi. “For example, with gastroenteritis, we can resuscitate patients with fluids and electrolytes to increase the fluid volume in their body and alleviate the low blood pressure.

If the hypotension is caused by blood pressure medications, the doctor will lower the dose or stop the medication, and the patient’s blood pressure will be closely monitored.

“For neurological problems like Parkinson’s and dysautonomia, treating these conditions with the right medication can help bring the patient’s low blood pressure back to normal.”

Remember that with proper care, most people with hypotension can lead healthy lives. Always consult your healthcare professional for advice.