Low Blood Pressure Causes


Low blood pressure is less common than high blood pressure, but for those affected is more likely to cause troublesome symptoms. Known as hypotension, low blood pressure is diagnosed when your blood pressure falls below 90/60 mmHg. Just as a blood pressure that is too high can cause problems, so can a blood pressure that is too low. Low blood pressure causes include hypotension syndrome, standing up quickly, and even eating, as well as serious causes such as loss of blood and heart attack.




Symptoms of low blood pressure

The signs and symptoms of hypotension include feeling light-headed or dizzy, with cold, clammy skin, a dimming or blurring of vision, buzzing in the ears and even fainting. You may notice that you also have a rapid pulse as the heart beats more quickly in an attempt to deliver more blood around the body to compensate for the reduced blood pressure. However, if your pulse is both rapid and irregular, this is a sign of an abnormal heart rhythm such as atrial fibrillation. If you have a rapid, irregular pulse you should see your doctor as soon as possible.

Other symptoms of low blood pressure are less obvious and non-specific such as tiredness, headaches, anxiety, depression and poor concentration which, together, are sometimes known as hypotension syndrome.

All of the symptoms of low blood pressure result from reduced blood flow to the brain, so that brain cells do not receive all the oxygen and glucose they need to function properly. The severity of symptoms therefore depends on the suddenness and severity of the fall in blood pressure.



Hypotension syndrome

Blood pressure is naturally low in some people, and this is sometimes hereditary – for example, because your kidneys are particularly good at flushing excess sodium from your body.

If you don’t have symptoms, hypotension does not necessarily need treating. Some people develop persistent headaches, fatigue, anxiety, poor concentration, however, and cannot function properly at work or socially. This is known as hypotension syndrome and needs to be resolved so you can get on with a normal life.

WorriedIf your doctor can find no underlying cause for your hypotension, the usual treatment approach is to suggest increasing your intake of dietary table salt (sodium chloride) and to avoid dehydration by drinking plenty of water (2 to 3 litres daily).

Avoid alcohol (which causes vasodilation), avoid rigorous exercise, and try not to become over-heated, which also causes blood vessels to dilate so blood pressure falls.

If you are taking any medication, check with a pharmacist whether or not this is contributing to the problem.

Korean ginseng for low blood pressure

Korean ginseng is often recommended as a treatment for hypotension syndrome. Herbalists class it as an ‘adaptogen’ as it helps the body adapt to physical or emotional stress, reduces fatigue and has a normalising action on many body systems, including the circulation. Traditionally, ginseng is not usually taken for more than 6 weeks without a break.

Select products standardised to contain at least 4% to 8% ginsenosides. These will generally be more expensive, but cheap versions may contain very little active ingredient.

 

Guarana  for low blood pressure

Caffeine is a stimulant, which helps to increase blood pressure by causing blood vessels to constrict. Drinking coffee is often recommended to treat hypotension syndrome. I prefer using Guarana, however, which is an extract from the seeds of a Brazilian rainforest shrub.

Guarana seeds, which have a rather alarming eyeball-like appearance as they burst from the fruit. Known in the Amazon as a ‘food of the gods’, dried guarana seeds contain a complex of natural stimulants, including caffeine (trimethyl xanthene), guaranine (tetramethyl xanthene), theobromine, theophylline and saponins similar to those found in Korean ginseng.

Guarana is an excellent natural source of caffeine as the saponins buffer its absorption to reduce the psychological over-stimulation and insomnia that can occur with caffeine.

Guarana is traditionally used to increase physical and mental energy levels, improve alertness and relieve fatigue.

NB Do not take any supplements if you are pregnant or if you are taking any other medications (check with a pharmacist for interactions first).

Low blood pressure and gravity

Gravity acts on blood in your circulation, drawing it downwards so that the average pressure in arteries below the level of your heart is higher than those above your heart.

When standing upright, for example, the average blood pressure (mid-point between your systolic and diastolic pressures) in arteries at the level of your heart is around 100 mmHg, while the average pressure in an artery in your foot is 180 mmHg average pressure but is just 62 mmHg for an artery in your head.

When you stand up suddenly from a lying position, the blood pressure falls in arteries taking blood to your brain. Blood also starts to pool in your lower leg veins so less is returned to your heart. Without a safety mechanism to prevent blood pressure collapsing, everyone would quickly faint on standing as blood flow to the brain would virtually cease. Instead, this sudden fall in blood pressure is detected by special cells (baroreceptors) in your heart and in your carotid arteries, which trigger several rapid reflexes. Your heart pumps more strongly, small arteries (arterioles) throughout the body constrict, blood vessels within the brain dilate, and circulating levels of certain hormones (renin and aldosterone) increase so that your blood pressure rises. Together, these rapid responses maintain blood pressure so that blood flow to the brain only decreases by less than 20% on standing, rather than the expected 60% or more which would make you black out.

As long as you keep moving while standing, the pumping action of muscles in your legs helps to keep blood flowing up from the lower half of your body back to your heart and then on to your brain. If you stand still for prolonged periods of time, however, such as when on guard duty, your blood pressure may slowly creep back down as blood pools in your leg veins due to the effects of gravity. Although you may feel embarrassed by fainting, it is an important, protective mechanism – by falling down, you lie flat so that blood flow to your brain is restored.

Low blood pressure on standing (postural hypotension)

MakebedIn some people, the protective reflexes are less rapid on standing so that a rapid drop in blood pressure occurs when standing up quickly from a sitting or lying position. This sudden fall in systolic blood pressure, of over 20 mmHg, is known as postural or orthostatic hypotension.

Postural hypotension affects between one in ten and one in twenty people in their 60s, and becomes more common with increasing age. It can also occur in people taking medication to lower a high blood pressure – if this is the case, see your doctor as your medication or drug probably needs changing.

The remedy is to get up slowly and, for example, sit on the side of your bed for a couple of minutes to allow your blood pressure to adjust before standing.



Low blood pressure after eating (postprandial hypotension)

When you eat a large meal, blood is diverted away from your muscles and general circulation to towards your digestive tract to boost the absorption of nutrients from your food. In some people, this can cause blood pressure to fall by more than 20 mmHg within two hours of eating, leading to dizziness, light-headedness or falls – especially in older people, and in those with diabetes and some neurological conditions such as Parkinson’s disease.

eatingIt will help to eat little and often, and to avoid heavy meals. Some people may be advised to take a nonsteroidal anti-inflammatory drug (eg ibuprofen) before eating as these cause salt to be retained and increase blood volume (but only do this if your doctor advises as side effects can occur as well as interactions with other medications you may be taking).

Drinking coffee with meals may also help as caffeine can cause blood vessels to constrict and prevent hypotension in some people. One study found that drinking two cups of coffee with a meal halved the incidence of postprandial hypotension but drink plenty of water to offset its diuretic effects.

Avoid caffeine with your evening meal if this will keep you awake, however.

Other causes of low blood pressure

There are other causes of hypotension, including pregnancy, hormone imbalances, heart problems and liver disease. A sudden catastrophic fall in blood pressure, with collapse, is known as clinical shock. This can be life threatening and can result from major blood loss, sepsis, heart attack or a severe allergic reaction to medication, bee venom or nuts, for example (anaphylactic shock).

If your blood pressure is low, self-monitoring is key to monitoring it to prevent going too low.

Click here for advice on choosing a blood pressure monitor to use at home.

See my recommended upper arm blood pressure monitors.

Do you have hypotension syndrome? Have you found a way to resolve your symptoms? Leave any questions or comments in the box below and I will get back to you as soon as I can.




Image credit: maridav / shutterstock; anita_fortis/wikimedia



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6 thoughts on “Low Blood Pressure Causes

  • Gina Gonzalez

    I have always had lower blood pressure and sometimes get dizzy. I have a checkup with my doctor soon and will ask her about it. I have a lot of fatigue also and sometimes I take Korean ginseng. It does help. Reading the effects of gravity, maybe I should lie down for a few minutes instead of sitting upright when I need a break. I do stand for periods of time in the kitchen and that is often where I feel lightheaded. This was very helpful. Thanks!

  • Blake

    Hypotension is a serious issue. I am glad you made this page to educate people on it. You really only ever hear of high blood pressure so I think it is good that you touched on the other side of things with your site. Knowing the signs and symptoms is instrumental

    • DrSarahBrewer

      Thanks Blake – it’s one of the things I get asked about most often as few peopel seem to know how to improve the problem, and many healthcare professionals don’t see it as an issue.

  • Nahim

    I have read other posts but here I found something different, becausete site starts off with the symptoms which in this case is low blood pressure, and it describes how that affects your health. You really helped me understand why hypotension is bad, but not only that because you also showed me what I could do to counter it.