Why am I always tired? Causes of fatigue and what to do

We all say “I’m tired” after a long week, but constant exhaustion is another matter. If you’re wondering, “why am I so tired all the time?” you’re not alone.

Fatigue isn’t just about a late night. Sometimes called long-term fatigue, it can have roots in your health, habits or stress levels. Here’s how to tell when tiredness has gone too far, and what you can do about it.

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Causes of tiredness and fatigue

According to the NHS, common causes of tiredness and fatigue include:

not getting enough sleep or finding it hard to get to sleep (insomnia)
an unhealthy lifestyle like having an unhealthy diet and not getting much exercise
stress, depression and dealing with life challenges - like bereavement or looking after a new baby
hormonal changes like during puberty, pregnancy or the menopause
illnesses like glandular fever and COVID-19
medical treatments and medicines, like chemotherapy or weight loss injections

Dr Daniel Atkinson, Clinical Lead at Treated, says: “People can feel tired for lots of reasons. Stress, diet, lack of sleep, or a busy work schedule can all make you feel tired. If you’re constantly tired and you’re not sure why, book an appointment with your GP. They will usually send you for blood tests to get a better idea of your health.

“Blood tests can also identify any vitamin deficiencies, such as iron, B12 or vitamin D, that are known to cause tiredness.”

Related: How to get rid of nausea, fast

Everyday habits that sap energy

Before you panic about a serious illness, look at your routine. Everyday habits that you may think are harmless might also be draining your energy. This is known as mental fatigue.

Simple things like living with clutter, multitasking, overthinking, overscheduling, procrastinating, lack of planning and technology overload may leave you feeling drained. Other bad habits like skipping meals, scrolling at midnight or drinking too much coffee can all chip away at your energy, too.

The good news is that awareness is the first step to overcoming these habits:

Look at your diet: Processed food and skipped meals mess with your blood sugar. Swap them for regular, balanced meals instead.
Your sleep quality: Keep consistent bedtimes, avoid caffeine after lunch and ditch screens an hour before bed.
Your stress levels: Life pressures can leave you running on empty. Gentle exercise and time with friends can help reset your system.

Dr Daniel advises: “If you’re tired all of the time, it’s worth trying to identify if your lifestyle is causing it. If you’re not getting enough sleep, focus on changing your routine rather than aiming for one night where you can ‘catch up’ on sleep.

“A healthy sleep routine can keep your energy levels up throughout the week. Regular exercise, especially in the daytime or early evening, can help you sleep better at night.”

A mum is tired while her children play on the sofa behind her

Could something in your lifestyle be causing your fatigue?

Can my diet really affect how tired I feel?

Yes, and you’d be surprised how much your diet can affect energy levels. Dr Daniel explains: “As for diet, trying to eat a varied, balanced diet that’s full of vital nutrients. Limit your intake of refined carbs and ultraprocessed foods, and try to eat as much fresh fruit and veg as you can.”

Blood sugar highs and crashes from processed food and skipped meals can leave you wiped out. Eating balanced, regular meals - with fruit, veg and whole grains - helps keep your energy steady.

Does being tired all the time just mean I’m getting older?

Not really. Your energy might shift with age, but extreme tiredness isn’t “just ageing”. It’s often down to something treatable, like thyroid issues or anaemia.

Conditions that can cause tiredness and fatigue

Ordinary tiredness usually vanishes after a good night’s sleep. However, fatigue lingers. It leaves you wiped out, interferes with daily life and can even affect your mental health.

If you’ve felt drained for weeks with no obvious cause, it’s time to take it seriously and speak to your GP.

Dr Daniel explains: “A blood test can identify issues like low iron, or an underactive (or overactive) thyroid. But speaking to patients can help give me an idea of their lifestyle and whether this explains their tiredness. For example, it’s perfectly normal for new parents to feel tired because their sleep is often broken up.

“More serious tiredness might cause other symptoms such as a rapid heartbeat or shortness of breath - this might be an indication that something more than lifestyle factors is behind it.”

Physical vs mental exhaustion

Not all fatigue feels the same, so it's useful to understand the different types of fatigue you might be experiencing.

Physical fatigue: heavy body, aching muscles, even climbing the stairs feels like hard work.
Mental exhaustion: brain fog, irritability, zero motivation.

They often feed into each other. Ongoing physical tiredness can bring on mental burnout, and vice versa. Knowing which one’s hitting hardest can help you work out the cause.

1. Sleep apnoea

Think you’re getting enough sleep? Poor sleep quality can make eight hours in bed feel like none at all. You might be waking at night, making gasping, snorting or choking noises at night or even snoring loudly. These are all signs of possible sleep apnoea.

2. Iron deficiency anaemia

If you're experiencing persistent tiredness, often with palpitations, breathlessness or pale skin - these are all signs of possible iron deficiency anaemia.

3. Diabetes

If you’re feeling very tired but also peeing more often than usual (particularly at night) and have experienced weight loss, these could be signs of diabetes. Other signs include feeling unusually thirsty and needing to urinate frequently. For diabetics who are taking weight loss injections, fatigue is a side effect, too.

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4. Overactive thyroid (hyperthyroidism)

Tired all the time? Finding it hard to stay still? These along with nervousness, anxiousness and irritability as well as muscle weakness can all be signs of an overactive thyroid, aka hyperthyroidism. Other signs include weight loss despite normal eating, tremors and heat intolerance.

5. Myalgic encephalomyelitis or chronic fatigue syndrome (ME/CFS)

If you’ve been experiencing extreme fatigue for at least three months (as in, it’s very hard to do daily activities), and you’re having problems with thinking, memory and concentration alongside flu-like symptoms, you may have ME/CFS. Speak to your GP about getting assessed for ME/CFS.

Are there any quick fixes for fatigue?

Sadly, there are no magic cures. A walk or a snack might perk you up for a bit, but lasting energy comes from fixing the cause: better sleep, a healthier diet, more movement and tackling stress.

Fatigue during pregnancy

When pregnant, it’s normal to feel tired or even exhausted - especially in the first 12 weeks.

According to the NHS, hormonal changes during pregnancy can make you feel tired, nauseous and emotional. The only answer is to rest as much as possible. Make time to sit with your feet up during the day and accept offers of help from colleagues and family when given.

Later in pregnancy, you may feel tired because of the extra weight you’re carrying around and as your bump gets bigger, it’ll be harder to get a good night’s sleep.

Some women experience insomnia during pregnancy, which can cause tiredness during the day. To help, try to relax before bedtime so you’re not wide awake. Relaxation techniques may help, and avoid napping in the afternoon or evening. Also avoid tea, coffee or cola drinks as the caffeine can make it harder to go to sleep.

A woman is tired working at her desk, she rubs her neck and back

Speak to your GP if your fatigue becomes too much

Fatigue when using weight loss injections

If you’re undergoing a medicated weight loss treatment, you might be feeling drained as a side effect. Fatigue is a recognised side effect of GLP-1 medicines such as Wegovy and Mounjaro, often related to reduced calorie intake, dehydration or blood sugar changes.

After all, you’re eating less. Since GLP-1 agonist receptor medications reduce your appetite, making you feel fuller for longer, you may be eating too little. This can contribute to fatigue. The injections also affect your metabolism by influencing hormones that regulate your blood sugar as well as your appetite. These metabolic changes can cause you to feel tired.

Other side effects could influence how tired you feel: diarrhoea, vomiting and nausea can all increase the risk of dehydration and electrolyte imbalances - both of which can cause tiredness and fatigue.

Eating enough nutrient-dense foods is one of the best ways to combat fatigue while on weight loss injections, and exercising regularly will boost your energy levels and improve your mood and sleep.

Fatigue during perimenopause

One of the most common complaints from women during this time of their lives is fatigue.

Perimenopause includes both the transition to menopause and the first year following your final menstrual period. During this time, you’ll experience hormonal fluctuations that result in irregular periods and vasomotor symptoms, like hot flashes and night sweats. These are caused by your body’s decline in oestrogen production.

It’s common for women experiencing perimenopause to feel tired and fatigued. This can be the result of a few things:

Hormonal changes
Underlying medical conditions
Sleep disturbances

In fact, difficulty sleeping and insomnia are two common complaints of women going through perimenopause. Establishing and/or maintaining healthy lifestyle habits can help you navigate this period of time and benefit your long-term health.

When to see your GP

Everyone gets tired sometimes. But if you’ve had unexplained fatigue for weeks, or it comes with symptoms like mood changes, chest pain or sudden weight changes, call your doctor.

Dr Daniel says: “If you’re constantly tired and you’re not sure why, book an appointment with your GP.”

They may run tests such as:

blood tests for anaemia, thyroid or vitamin levels
urine tests for infection or kidney issues
a sleep study if sleep apnoea is suspected

Feeling tired all the time isn’t something you just have to live with. From diet tweaks to medical checks, there are ways to tackle fatigue and get your energy back. And if you’re worried, trust your gut and see your GP - better to rule out something serious than keep dragging yourself through the day.

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🔎 This article has been medically reviewed

Last reviewed in September 2025 by Dr David Porter MBBS, MSc, PgDip, an internationally renowned sports medicine physician and Founding Director of Opus.

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About the expert

Dr Daniel Atkinson is the Clinical Lead at Treated.com, an online healthcare service company.

About the author

Our resident Leeds lass, Rebecca Roberts is a Senior Content Editor here at Mumsnet. On a daily basis, she commissions, writes and edits content designed to help parents navigate real life - from product reviews to practical features on everything from sex and relationships to fashion to skincare.

Rebecca - aka Beccy - brings unique personal insight to weight loss content here at Mumsnet, having undergone her own journey with medically supervised injections. Her firsthand experience with GLP-1 treatments provides authentic expertise that resonates with parents exploring similar options.

Beyond her role as an editor, she can be found balancing life as a working mum of two toddlers and when she’s not at her desk, you’ll likely find her at a PTA meeting, in a nearby coffee shop, or walking her two dogs up and down country lanes.