Low blood pressure

• Being dehydrated (needing to drink more water) especially from vomiting and diarrhoea or hot weather.
• Overheating such as after a hot bath, being in a hot room or outside on a hot day.
• Prolonged bed rest or sitting or as a result of moving less.
• Severe injury such as burns or if you've lost a lot of blood. Low blood pressure can also occur if you go into shock after having a serious injury.
• Having an infection  If you have a sudden drop in blood pressure during an infection, it can be a symptom of septic shock, which is a life-threatening condition.
• Having a severe allergic reaction to something, for example, a wasp sting or a peanut can cause anaphylactic shock, or anaphylaxis which is a life-threatening condition.
• Being in severe pain.
• Excessive alcohol intake or taking drugs.
• Having an underlying illness, eg, a heart condition, anaemia, diabetes or a hormonal or nervous system disorder.
• Some types of medicine, eg, medicine to reduce high blood pressure or treat Parkinson’s Disease, as well as diuretics (water tablets) and some antidepressants.

Note: Low blood pressure is fairly common during pregnancy, especially during the early to mid stages of pregnancy.

Postural hypotension

Postural (or orthostatic) hypotension is a particular type of low blood pressure that happens when you change position. While you are sitting or lying your blood pressure is normal but it drops suddenly when you stand up making you feel light-headed or dizzy. It can also happen if you're standing still for too long. 

• Postural hypotension can occur at any age but is more common for older people.
• This is mainly because special cells that control blood pressure (called baroreceptors) near your heart and neck arteries, can respond more slowly as you age. This means that the amount of blood being pumped by your heart, and your blood pressure, doesn't adjust as quickly as it used to when you change position.
• It can also be harder for your heart to speed up to make up for drops in blood pressure.
• Postural hypotension is of particular concern in older adults because of the increased risk of falls and injury. 

How is low blood pressure diagnosed?

See your healthcare provider if you often have the symptoms listed above. They will measure your blood pressure and ask you questions about your medical history and lifestyle. They might refer you for blood tests or an electrocardiogram (ECG) to see if there are any underlying conditions causing your low blood pressure.

How is low blood pressure treated?

• You can use simple lifestyle measures to ease your symptoms – see the self-care section below.
• If you have an underlying health condition causing low blood pressure, this needs to be treated, or if your medicine is lowering your blood pressure, this will need to be reviewed.
• Your healthcare provider may recommend that you wear support stockings. This reduces the pooling of blood in the legs which helps to boost blood pressure throughout your body.
• Occasionally people are prescribed medicine for hypotension. If your low blood pressure is causing you to fall a lot despite other treatment options, your healthcare provider may refer you to a specialist. They will assess whether you need medicines to raise your blood pressure.

There are things you can do to reduce the symptoms of low blood pressure.

• Drink enough water throughout the day to avoid dehydration. Limit alcohol because alcohol can cause dehydration and dilation of blood vessels.
• Take your time when changing position, eg, when getting up from a chair. Get out of bed slowly. First sit up, sit on the side of the bed, then stand up. To prevent falls, make sure you have something to hold on to when you stand up and don’t walk if you feel dizzy. Read more about preventing falls.
• Avoid taking very hot baths or showers and saunas. It may be helpful to sit down when washing, showering, dressing, or working in the kitchen. 
• Prop your head up with pillows when you’re in bed (or raise the head of your bed) to reduce the likelihood of postural hypotension when you get up.
• Ask your healthcare provider whether you need more salt in your diet. However, it’s not common to have too little salt as most people in Aotearoa New Zealand eat more than their body needs. As an adult you only need about 1 to 2g of salt (460 to 920mg sodium) per day to function.

If you want to track your blood pressure yourself, talk to your healthcare provider about getting a device to do so at home. You can track your readings over time using an app (see below).