Close up of sweating water drop on face asian woman.

Why do we sweat a lot?

Primary focal hyperhidrosis

One of the most common causes of excessive sweating, primary focal hyperhidrosis, isn’t a sign of a serious illness. This condition usually manifests as symmetrical excessive sweating, meaning that it will happen on both sides of your body eg both hands. It most commonly causes excessive sweating under the arms.

It isn’t clear what causes primary focal hyperhidrosis but it’s thought to be a problem in the nervous system that’s passed on genetically. It causes the body to produce sweat when it isn’t needed to cool you down.

Thyroid issue

The thyroid is a gland in your neck that produces thyroid hormones. These hormones are vital to a range of processes that occur in your body, including controlling your energy levels, internal temperature, metabolism, weight, and skin, hair and nail growth.

If you have an underactive thyroid, it’s more likely that you will be sensitive to heat and experience excessive sweating. This is made worse by the fact that an underactive thyroid is more likely to result in you being overweight or obese, which can make you more prone to feeling hotter.


If you have diabetes, you may experience excessive sweating in a few different situations:

Low blood sugar is the most common cause of excessive sweating due to diabetes. When your blood sugar levels drop too low, it causes your body to produce more adrenaline, which then causes sweating. This can happen during the day but can also cause night sweats when you have diabetes.

Teen boy takes a blood sample for diabetes with lancet pen. Problems of diabetes

Controlling your blood sugar levels if you’re diabetic will help you control any excessive sweating. When it comes to night sweats, altering your diet, and when you eat and exercise can help reduce these by better regulating your blood sugar levels while you sleep.


Certain medications can cause excessive sweating. If you’ve been prescribed a new medication and suddenly have started sweating more than usual, this may be the cause.

Antibiotics and medication

Certain antidepressants (eg selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants), opioid painkillers and cholinesterase inhibitors, which are used to treat dementia, can all cause excessive sweating.

Changing hormone levels

Changes in your hormone levels can trigger excessive sweating. In women, hormone changes are experienced during pregnancy and during perimenopause, which occurs before the body goes through menopause.

stethoscope with the words perimenopause, menopause and postmenopause.

Changes in oestrogen levels affect how your body controls its temperature, which can lead to hot flushes and excessive sweating as your body works hard to cool you down.


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