Spotting the difference: Night sweats in leukaemia VS normal night sweats

Although most people welcome the warm weather, for many, the arrival of summer can also mean welcoming the unpleasant feeling of night sweats. It can be all too easy to dismiss an increase in night sweats as just a harmless symptom of summer. However, severe night sweats can sometimes be a sign of leukaemia. Read on to spot the difference between harmless and harmful night sweats.

Although most people welcome the warm weather, for many, the arrival of summer can also mean welcoming the unpleasant feeling of night sweats.

It is certainly not unusual to sweat during the night, especially in the summer when your room or bedding becomes too hot. However, severe night sweats that occur to an extent that your bed sheets or pyjamas become soaking wet, despite sleeping in a cool environment, can sometimes be a sign of leukaemia. Out of over 2,000 leukaemia patients asked in our survey, 31% reported night sweats as a major symptom before their diagnosis.

It is all too easy to dismiss an increase in night sweats as just a harmless symptom of summer. Read on to spot the difference between harmless and harmful night sweats and stand a greater chance of diagnosing leukaemia earlier.

In hindsight, the night sweats were a big give away. It wasnt just a bit of a hot night, it was sheets drenched. Having a shower in the morning because you’re just sweating so badly Its an unnatural type of sweat at night.

Spotting the difference

Sweating is the body’s natural way of cooling down. It happens to everyone throughout the day and most people will also sweat to some degree during the night. The key difference between harmful and harmless night sweats is the quantity of sweat, and the temperature at which they occur. Night sweats caused by illness are more than just breaking a light sweat because you have too many layers of bedding. Instead, they cause you and your bed sheets to become soaked to the extent that you can no longer sleep on them, often when your room is at a comfortably cool temperature.

It is important to visit your GP if:

  • You regularly have night sweats that wake you up at night – You may wake up drenched in sweat, unable to cool down even if your room is cool. Many describe the feeling as if they had just got out of a swimming pool and laid down in bed.

“There were a couple of occasions where I woke up in the middle of the night drenched with sweat, feeling like I was in a sauna.”

  • You have never experienced night sweats before – Night sweats that occur fairly consistently and constantly throughout the night and in small quantities are generally harmless. Unfamiliar night sweats that happen suddenly in hot flashes are more concerning.

I had a few nights where I would get very bad night sweats – something that has never happened to me before.

  • You are having severe night sweats but can’t work out why, i.e. you are sleeping in a cool environment.

“My night sweats were transient, I’d end up experiencing a week of night sweats, and then nothing.”

  • You also have a fever, a cough or diarrhoea – Generally, fevers and chesty coughs are caused by infections. If this is the problem, your doctor will be able to prescribe antibiotics. However, be sure to return if symptoms persist. Leukaemia can cause repeated infections by weakening your immune system.

“The night sweats were awful, and I had a temperature and felt like I had the flu a few days before diagnosis.”

  • You are experiencing unexplained weight loss alongside your night sweats – Rapidly dividing leukaemia cells use up energy that your body would otherwise use or store as fat, causing weight loss.

“I also noticed a change in my weight and I lost my appetite.”

  • You are also displaying other symptoms of leukaemia – As well as night sweats, you may be experiencing seemingly unrelated symptoms that when linked together could in fact be an indication of leukaemia. Other symptoms of leukaemia can include fever, bruising, breathlessness, bone pain, abdominal pain or frequent infections.

“I became bed bound with debilitating headaches, bruises, drenching night sweats, fatigue, no appetite, nausea, weight loss, nose bleeds and bone pain.”

What causes night sweats in leukaemia?

There are a few different ways that leukaemia can lead to night sweats:

  1. Leukaemia puts you at a greater risk of developing infections because your body isn’t producing enough immune cells. During an infection, the body will automatically increase its temperature to help fight against infections, causing both fever and night sweats.
  2. In the same way that your body naturally rises in temperature when fighting an infection, your body will rise in temperature in an attempt to kill the leukaemia cells. This is part of the “inflammatory response”.
  3. After diagnosis, many treatments including chemotherapy can produce toxic by-products that can also lead to a raise in core body temperature.

Other causes of night sweats:

It is important to remember night sweats are rarely caused by leukaemia. Nearly always there is another explanation. For example, the most common cause of night sweats in women over 40 is menopause. Generally, leukaemia is only a worry if you present with other associated symptoms such as fatigue, bone pain, bruising or weight loss. By visiting a GP, your doctor will be able to gather a detailed medical history and order appropriate tests to confirm which of the following conditions is the cause of your night sweats:

Menopause (“hot flushes”)

Pregnancy – Both pregnancy and menopause can cause night sweats through hormonal changes that naturally occur in the body.



Medications – Antidepressants, for example, are a common cause of night sweats.

Hormone disorders e.g. hypothyroidism

Hypoglycaemia (low blood sugar) – Diabetics can often get night sweats if blood glucose levels fall during the night.

Drinking alcohol – Alcohol causes blood vessels to dilate, leading to sweats.

Idiopathic hyperhidrosis – Sometimes, the cause of excessive sweating is unknown, but is harmless. This is called idiopathic hyperhidrosis.

When should I be concerned?

Since there are multiple other conditions that can cause night sweats, a full examination by your GP is necessary to accurately determine the cause and rule out any serious underlying issues. If you are regularly waking up with your bed sheets drenched in sweat, you should certainly get it checked by a GP.

Night sweats that occur due to leukaemia will usually be experienced alongside other symptoms such as fatigue, weight loss or excessive bruising. The night sweats may also present in the daytime as fever, or can lead to sleeping problems.

Knowing what other symptoms are typical of leukaemia is crucial for helping you to make the decision to visit your GP sooner for a blood test. Connect the dots between the symptoms of leukaemia and spot leukaemia sooner.

For information on the other symptoms of leukaemia, click here.

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