Medical conditions that make you tired

Lesley Dobson / 09 November 2016 ( 20 February 2019 )

Find out which conditions could be sapping your energy.

We all feel tired from time to time, but the kind of tiredness and fatigue that leaves you struggling to live a normal life, can be a warning sign, and needs investigating.

Are you tired all the time?

This problem is remarkably common. According to the Royal College of Psychiatrists at any one time one in five people feels unusually tired, and one in 10 have prolonged fatigue.

There are a range of medical conditions that can cause this kind of debilitating exhaustion. We’ve looked at some of the most common, with their symptoms.

Why am I so tired?


Iron deficiency anaemia can make you feel tired because having this condition means that you have fewer red blood cells than you should have. Iron is used to create your red blood cells. These then help to carry oxygen in your blood to organs and body tissue. Not having enough red blood cells means that vital parts of your body don’t get enough oxygen, which leaves you feeling exhausted.

Talk to your GP about having a blood test. If you are anaemic they may suggest taking iron supplements to bring your iron levels back to normal.

How much iron do I need?

Chronic Fatigue Syndrome (CFS)/Myalgic Encephalomyelitis (ME)

The main symptom of this condition is long-term tiredness (fatigue), which is so extreme that its effects are disabling. The fatigue that comes with CFS/ME has a starting point – you may remember when you suddenly started feeling overwhelmingly tired – and feels quite different to other kinds of tiredness. If you’ve had a physically active day, you’re likely to feel even more fatigued on the following day. This can last for a few days before it starts to improve.

Other symptoms can include: 

  • poor and erratic sleep patterns
  • painful joints and muscles
  • poor concentration
  • poor memory

It’s estimated that about 250,000 people in the UK have chronic fatigue syndrome, but that figure could be higher. The symptoms can start to show quite gradually, but can also come on more suddenly, over just a few days.

CFS/ME can develop at any age, and can wax and wane, lasting from a few months, to decades. The symptoms can go, and you can have long periods feeling better, but it can reappear, and knock you for six again.

The severity of symptoms can vary too. Some people go through periods when CFS/ME fluctuates, so they have good and bad patches. The bad periods can be brought on by high stress levels, high or low temperatures, and illness or surgery.

A smaller group of people with CFS/ME has more severe symptoms that means that they need long-term help and support.

A fairly small section of all of those affected with this condition do regain their health, although this can take quite a long time.

In a few cases, people with CFS/ME can carry on deteriorating, which is unusual in this condition. In these cases it’s important to see an expert, so that other conditions can be ruled out.

According to the ME Association, there is no accepted cure for this condition, and there is no robust evidence for an effective treatment that works for all people with ME.

You can find out more about ME/CFS at


Type 2 Diabetes is a complex condition, and symptoms include extreme tiredness and fatigue in people with diabetes.

People with diabetes have a high blood sugar level, (either because of a lack of insulin, or from insulin resistance) which is caused when insulin levels are too high for too long.  This is because the high blood sugar levels can interfere with how well your body can transfer glucose from your blood to your cells. This then affects the amount of energy you have, and can make you feel extremely tired. Ask your GP to check you for diabetes.

If you are taking drugs for diabetes, you need to monitor your blood sugar levels as these drugs can cause blood sugar levels to drop too low. This is known as hypoglycaemia, and it when it happens it will make you feel very tired. If this happens, you, someone close to you or a doctor need to raise your low blood glucose levels, quickly.

The best foods to help regulate blood sugar

Underactive thyroid

We all have a thyroid gland (it’s positioned in your neck), which produces two hormones that travel around your body in your blood. They are thyroxine (T4) and triiodothyronine (T3), and their job is to make sure that all the cells in our bodies do their jobs and work normally.

However, the thyroid gland can be damaged, by an assault from the immune system, or by the treatment for an overactive thyroid. This can leave you with an underactive thyroid gland – also known as hypothyroidism – which produces too little of the thyroid hormones you need to keep your body running smoothly.

One of the main symptoms of an underactive thyroid is tiredness, but you may also have a slower than normal heart rate, depression, and aching muscles.

In the UK 15 out of every 1,000 women, and 1 in 1,000 men are affected by this condition.

A blood test can check your hormones, and confirm if you have an underactive thyroid gland. Your doctor will be able to prescribe hormone replacement tablets – levothyroxine – which boosts your thyroxine levels, and should make you feel better.

Vitamin D deficiency

Vitamin D is important for our health in many ways – keeping our bones and teeth strong and healthy for instance. It’s only relatively recently that scientific studies have found that lack of vitamin D can cause tiredness and fatigue in people who are otherwise healthy.

Our main source of vitamin D is sunshine. When sunshine hits our bare skin our bodies can create vitamin D. Be careful not to overdo it, and stay out in the sun for too long without protection as you may burn. Spending a short period of time in the sun every day, without suncream, and with bare arms and lower legs from April to September should be enough to make the vitamin D you need.

Vitamin D vs skin cancer: getting the balance right

You can also get vitamin D from foods, including some breakfast cereals, oily fish (salmon, mackerel, sardines and herrings), eggs and red meat. Vitamin D tablets can also help top up your levels.

10 ways to boost levels of vitamin D

Anxiety, stress and depression

Mental health issues can play havoc with your sleep. If you are feeling stressed or anxious it can be hard to get off to sleep because of the thoughts and worries buzzing about in your head. You can also struggle with disturbed sleep, and wake up throughout the night, or have nightmares, and even start sleep walking.

Anxiety solutions

If you struggle with these sleep problems for some time, they can then be the cause of more anxiety and/or phobias about getting off to sleep. This can make your sleeping problem even worse.

Strategies for beating insomnia

Depression can also lead to sleep disruption, particularly disturbed sleeping patterns, especially sleeping through the day. Oversleeping can bring on insomnia, exacerbating your sleep problems. And if you aren’t sleeping well, or for long enough, this can leave you feeling utterly exhausted, and struggling with daily life.

Talk to your GP about ways to help tackle the underlying problems of anxiety, sleep and depression, and take a look at the article sleep: strategies for a better night’s rest, on our website: 

The opinions expressed are those of the author and are not held by Saga unless specifically stated.

The material is for general information only and does not constitute investment, tax, legal, medical or other form of advice. You should not rely on this information to make (or refrain from making) any decisions. Always obtain independent, professional advice for your own particular situation.