What causes tiredness and when should you see a doctor?

What causes tiredness and when should you see a doctor?

Print Friendly, PDF & Email

What causes tiredness and when should you see a doctor?

We can all feel tired from time to time, but when tiredness hangs around for weeks or months it can start to make people worry there’s something wrong, and they’ll often come to the doctor for a check up.

The good news is that it’s rarely a sign of anything serious- though sometimes it can take a while to figure out what’s causing it, as there are many aspects of physical and mental health that need to be considered.

Here are 10 common causes of tiredness that doctors will usually consider. Some may seem obvious, but often the simple things, such as a good night’s sleep, have been overlooked!


Very often a patient will come to the doctor saying, “I’m tired and I don’t know why”, but when asked about the quality of their sleep they’ll immediately admit they are not getting enough, or that it’s broken and irregular. There may be an obvious disruption to sleep, such as working night shifts or parenting a baby who wakes a lot. Sometimes, the sleeping environment itself needs attention- in terms of light, noise or temperature. Others will admit they are not “switching off” properly for one reason or another- this might relate to stress, using screens, caffeine or smoking late into the evening.

There are also some medical conditions that can affect sleep. Hyperthyroidism (overactive thyroid) and depression can cause insomnia and Obstructive Sleep Apnoea can significantly reduce sleep quality, often leading to tiredness by day. Too much sleep can also be a bad thing- if an adult regularly sleeps for more than 11 hours a night it can actually cause a vicious circle of increased tiredness!

The ideal amount of sleep varies from person to person, so it’s not necessarily about hitting a certain number of hours- it’s more about sleeping enough to function well, feel rested and refreshed. If sleep is a problem or you have insomnia, it’s worth speaking to your GP, as there are many factors which need to be explored.

Learn more about our online doctor services


Physical Exercise

Many of us do not get enough physical activity throughout a normal working day, particularly if deskbound. It may be hard to find the time, but even a 30-minute work-out or brisk walk in the morning or at lunchtime can make a difference to energy levels. And on days off or weekends, it’s worth trying to do a little more.


Again, this is an obvious one- but if you’re not eating healthy, balanced meals each day, or are reaching too often for quick fixes like sugar, caffeine and soft drinks, it’s likely you are not giving your body the fuel it needs, and tiredness may occur. If you’re struggling with this, a session with a dietitian may help with meal and snack planning to fit your daily routine.

Alcohol and drugs

If you drink a lot of alcohol or take recreational drugs, it can have major impact on your energy levels- cutting out these culprits will often make a massive difference. If you have difficulty cutting back, you should speak to your doctor or a counsellor.


Tiredness can also be a side effect of medications- such as antihistamines (even supposedly “non-drowsy” ones), antidepressants, blood pressure tablets and others- so, check with your doctor if you’re not sure.

Iron Deficiency Anaemia

Anaemia is when your Haemoglobin is low. Haemoglobin is an oxygen-carrying protein in red blood cells- if Haemoglobin levels are low, all systems of the body can be affected- and tiredness is a common symptom. Haemoglobin is made up of iron- so if you don’t get enough iron, or if you are losing blood for some reason, anaemia can happen. There are many causes for iron deficiency anaemia, but some are much more common than others. In women, heavy periods are often to blame. Other causes include lack of iron in the diet (particularly in vegetarians and vegans) or blood loss through the gut (coeliac disease, inflammatory bowel disease, bowel cancer). Iron deficiency anaemia is confirmed by a full blood count and iron studies. By taking a thorough history, examination and further tests, your doctor will usually be able to figure out the underlying cause.



The thyroid gland is located in the front of your neck. It produces thyroid hormone, which regulates growth and how your body spends energy. When it is underactive (hypothyroidism), people often complain of tiredness. Some will also notice other symptoms, like feeling cold all the time, low mood, hair loss, weight gain and reduced sex drive. Women may experience changes in their menstrual cycle. It’s diagnosed via a blood test, known as a “thyroid function test” or TFT.

Stress, Anxiety and Depression

If you have ongoing stress due to work, financial concerns, personal issues, or a combination of these, it can lead you to be in a constant state of “overdrive”, which can lead to fatigue.

Similarly, anxiety disorders, can cause people to frequently be in “fight or flight” mode, which can be exhausting over time.

Tiredness is also a well-known symptom of Depression. Other symptoms include an inability to enjoy oneself or feel happy, poor concentration and motivation, low self-esteem and changes in appetite and sleeping patterns.

If any of these issues sound familiar, you should speak to a GP as there are positive steps you can take to improve your mental health.


Viral illness

Any viral illness can cause tiredness. However, in most cases this just lasts for a few days, until the virus is cleared from your body. However, some viruses can lead to tiredness for weeks or months. Your GP may check you for the viruses that cause Glandular Fever (EBV and CMV), particularly if you’ve recently had a sore throat or a rash. Ross River Fever is another potential culprit- it can lead to several weeks of bad fatigue. With most viral illnesses, there is no specific treatment- the body will recover over time.

Other systemic illness

Many other conditions can lead to tiredness- including low Vitamin B12, heart disease, diabetes, kidney disease and autoimmune illnesses. However, in most cases, there will be other signs and symptoms that will help your doctor make the diagnosis.

When should I see a doctor with my tiredness?

  • If you have other symptoms with it- such as fever, breathlessness, chest pain, dizziness, weight loss or a skin rash.
  • If it continues for more than a week or two, and there’s no obvious cause
  • If you think you have depression or anxiety
  • If you’ve already seen a doctor about it, but the tiredness does not improve or gets worse, you should go back for a reassessment.
Learn more about our online medical certificate service

Mycoplasma Genitalium- a common STI that people don’t know about

By | February 13th, 2018|Categories: Sexual Health|

Mycoplasma Genitalium- a common STI that many people don't know about What is Mycoplasma Genitalium? Most people have heard of STIs such as Chlamydia, Gonorrhoea and Genital Herpes, but there is much less [...]

Comments Off on Mycoplasma Genitalium- a common STI that people don’t know about

Think smoking one a day is ok? Think again.

By | February 5th, 2018|Categories: Our Blog, Heart and Circulation, Lung & Respiratory Conditions, Nutrition & Lifestyle|

Does cutting down make a difference? “Yeah, I still smoke, but I’ve cut right back, I’m down to one or two a day” These are words doctors often hear when they ask people about [...]

Comments Off on Think smoking one a day is ok? Think again.
2017-11-06T20:04:19+00:00 By |Our Blog, Nutrition & Lifestyle|

About the Author:

Aifric Boylan
Originally from Ireland, Dr Boylan is an experienced GP based in Melbourne. She is also committed to innovation in the area of online medicine and health technology. Aifric is a keen distance runner, and plays the violin, but not at the same time…

9.3 out of 10
reviewed by Trustpilot