Low blood pressure (BP), or hypotension, can give symptoms of feeling lightheaded, dizzy, feeling a bit weak, sick, disorientated and suffering momentary blurred vision. It can cause you to faint. It may also cause no symptoms. It’s diagnosed when a BP machine gives a reading of less than 90/60 mmHg. A healthy BP should be 100-120/80-90 mmHg. You might have a slightly faster heart rate (the third number on the BP machine) to make up for the low BP, in order to keep blood flowing to your vital organs.
A low BP may be normal for you, especially if close family members have the same, or if you’re young and fit. It can be a normal part of pregnancy and blood vessels adapt to changing hormones, then returns to normal after delivery. Dehydration is a common cause, so ensure you stay hydrated, especially after exercise or in hot climates. Certain medications can cause BP to become low, especially medication to treat high BP (hypertension). In more extreme situations, it may occur if you’re very unwell with an infection or sepsis, or in an accident or injury where you have severe blood loss.
If you feel lightheaded, dizzy or faint when you stand up, you may have postural hypotension (also called orthostatic hypotension). This is where your blood pressure drops considerably on changing position, and it takes a good while for it to climb back up. Your nurse or doctor can check this. A diagnosis is made if your BP drops by 20 mmHg or more on the top number (the systolic pressure), or by 15 mmHg or more on the bottom number (the diastolic pressure), and this remains so for a minute or more. It can be more common in the elderly or those who have had a prolonged period of bed rest.
There are simple measures you can take to make sure things don’t get worse: make sure you stay well-hydrated, especially if it’s hot or you are unwell with a fever. If moving from lying or sitting to standing is a trigger, make sure you take a few minutes to hold onto something and get your balance, before walking off. It can be more common in the elderly or those who have had a prolonged period of bed rest.
If you suffer these symptoms on a regular basis, you should get your BP checked with either your doctor's practice nurse or at a pharmacy. Alternatively, you can book a routine appointment with your doctor to discuss symptoms and review any medications you’re taking. They may suggest further investigations such as a blood test or ECG (electrocardiogram that traces the electrics of your heart).