8 Possible reasons for feeling constantly tired

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Tired girl sleeping on the table of the kitchen at breakfast; Shutterstock ID 457502776

Tiredness is something we’ll all experience towards the end of a typical day. It’s a natural feeling caused by the release of the hormone melatonin and is a signal to the body that it needs to sleep.

Most of us will know firsthand that it’s common to feel more tired during busier periods in our lives, as we’re less likely to be getting the amount of sleep we need.

However, feeling constantly tired, throughout the day and over a sustained period of time, can have a negative impact on our physical and mental well-being. Persistent tiredness can also sometimes be an indication of an underlying health issue or a sign that there’s something wrong with our lifestyle.

If you are tired all the time and aren’t sure why you should speak to your doctor for help. They should be able to help you identify the cause of the problem, and offer advice.

In this post, we’ll take a look at some of the possible reasons why someone might be constantly tired, and what they can do to help tackle the problem.

Lifestyle factors

Various lifestyle habits can increase the likelihood of feeling tired all the time. Examples include:

Excessive alcohol use

The term ‘nightcap’ is one most of us will be familiar with. But the notion that alcohol aids sleep is actually something of a misconception; particularly for those who regularly drink to excess.

The sedative effect of alcohol can make you initially more tired. However, during sleep, the body will release hormones as a response to alcohol consumption, and these can make you more likely to wake up in the early hours of the morning. So someone who regularly drinks a lot may find that they are able to sleep less, and therefore more tired.

Keeping within the lower risk guideline threshold of no more than 14 units per week, as well as limiting the amount you drink in a single session (to no more than 6 units), can help to reduce the likelihood of developing alcohol-related sleep problems.

Poor diet

Eating a balanced and healthy diet helps your body to get the nutrients it needs, many of which are essential in maintaining good energy levels. Fruit and vegetables are particularly important for vitamins; and for people who eat fish, omega-3 can help to prevent lethargy.

A poor diet on the other hand can have the opposite effect, and make someone more likely to feel tired. For example, eating sugar- and calorie-dense food on a regular basis can cause someone’s blood sugar level to dramatically spike and dip, making them more susceptible to feelings of tiredness.

Consuming a large meal in one sitting, high in calories, obviously gives the body a lot to do; digestion requires energy, and the more it spends trying to process a large meal, the more tired you’re likely to become. So rather than eating one or two large meals, it can help to eat smaller meals more often throughout the day.

People who continually don’t consume enough calories can develop persistent tiredness as well, as the body simply won’t have enough energy to perform the functions it needs to.

So it’s vital then to try and stay close to or just below your recommended reference intake. The general guidelines for women and men are 2000kcal and 2500 kcal respectively, but you may be advised to consume a little less than this if you’re trying to lose weight.

Drinking lots of caffeinated drinks can also make you feel tired. This is because caffeine initially stops adenosine receptors in the brain from getting adenosine, a hormone that can induce tiredness. However, once the build-up of adenosine filters through to the brain, it can lead to a ‘caffeine crash’ which causes tiredness.

It’s advisable then to reasonably limit caffeine consumption. There are differing opinions on what amount (if any) is the optimum amount, but staying under 400mg per day (roughly the equivalent of four small cups or two large cups of instant coffee) is recommended.

Lack of exercise

Regular exercise helps to maintain energy levels; it helps to get the blood moving around the body and gets oxygen to the places where it needs to be.

People who have more sedentary lifestyles may be more prone to tiredness; because they’ll generally have lower energy levels, but long-term are also more susceptible to chronic health problems which can induce perpetual tiredness as well, such as diabetes.

So if you’re feeling tired all the time, it can help you to get active. This might be walking more, joining the gym, or taking up a sport.

Mental health problems

Sometimes, persistent tiredness can be the result of an underlying mental health issue. Some examples might be:


There are several reasons why someone who has depression may feel tired more often.

For instance, someone who is depressed may be more inclined to be inactive because the prospect of doing certain things may seem daunting; and the more inactive someone is, the less energy they’re likely to have.

Someone with depression may also experience problems sleeping at night due to stress or worry, thereby disrupting regular sleep and causing them to feel tired during the day. Furthermore, medication for depression can also sometimes cause drowsiness or lethargy as a side effect.

If you think you may be experiencing depression, it’s important to speak to a healthcare professional so that they can help you to address the problem.

Anxiety or stress

People who are continually anxious or stressed, be it due to a large workload or personal difficulties, may feel tired all the time due to the hormonal effect these feelings have.

Cortisol and adrenaline are hormones our bodies release in response to stress; they’re intended to help us cope better and stay alert in dangerous situations. But the prolonged release of these hormones can make us more tired.

Again, if you’re feeling tired due to constant stress or anxiety, it can help to take a look at what might be causing these feelings, and talk them through with someone.

Underlying medical conditions

There are several illnesses that can make someone feel tired more often, such as:


Anemia causes iron deficiency in the blood, which means that blood cannot get around the body as easily. As a result, people who are anemic are more susceptible to tiredness, weakness, and lethargy, because the cells in their bodies aren’t getting the oxygen they need.


One of the most common symptoms of type 2 diabetes is tiredness. This can be put down to the lack of control of glucose in the blood, which often leads to hyperglycemia or high blood sugar levels. Fluctuating blood sugar levels also lead to spikes in energy, dehydration, and, in turn, tiredness.


Having an underactive thyroid means that the body does not produce as much thyroxine as it should. Thyroxine is an important hormone, which aids in the metabolic process and helps to convert energy. If there isn’t enough thyroxine made by this gland, it can therefore lead to loss of energy conversion and tiredness.

Once more, if you are experiencing constant tiredness but are not sure why, you should arrange to see your GP. If an underlying physical or mental health problem is the reason, they’ll be able to assist you in getting the attention you need.

If it isn’t, they’ll be able to give you advice on what to do differently.

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Tom Perry, M.D., attended Tulane University and graduated Magna Cum Laude with a B.S. degree in Parasitology. He received his M.D. degree in 1983 from the University of Virginia School of Medicine, where he gained extensive research experience, including studies conducted through the National Institutes of Health.