If you're always tired despite getting enough sleep, you're not imagining it. Fatigue is one of the most common complaints GPs hear - and one of the most misunderstood.
The problem is that most people assume tiredness is just about sleep. Get more hours, fall asleep, feel less tired. But if it were that simple, you wouldn't be reading this.
Feeling tired all the time is rarely about one thing. It's usually a combination of factors quietly draining your energy levels - some obvious, some surprisingly overlooked. Here are seven of the most common reasons you're exhausted, and more importantly, what you can actually do about each one.
1. You're Not Getting Enough Quality Sleep - Even If You Think You are
There's a difference between not enough sleep, enough sleep and good sleep. Most adults need seven to nine hours, but sleep quality matters just as much as sleep quantity. You can spend eight hours in bed and still wake up feeling exhausted if your sleep pattern is disrupted, you're not reaching deep sleep stages, or you're waking frequently through the night.
Poor sleep habits are one of the most common causes of daytime fatigue. Inconsistent sleep schedules, screen exposure before bed, a room that's too warm, or high cortisol levels at night can all fragment your sleep without you realising it.
Sleep disorders like insomnia and obstructive sleep apnea are also significant contributors to waking up tired. Sleep apnea in particular - where breathing during sleep is interrupted repeatedly - is frequently undiagnosed. If you snore heavily, wake with headaches, or feel exhausted regardless of hours slept, a sleep study may be worth discussing with a healthcare provider.
What helps: Consistent sleep and wake times, a cooler bedroom environment, no screens for 60 minutes before bed, and addressing magnesium levels - which we'll come to shortly.
2. Low Magnesium Levels Are Draining Your Energy
This is the one most people miss entirely.
Magnesium is involved in over 300 biochemical reactions in the body, including the production of ATP - the molecule your cells use for energy. When magnesium levels drop, your body struggles to produce energy efficiently at a cellular level. The result is persistent fatigue that no amount of sleep seems to fix.
Magnesium deficiency is also one of the most common nutritional deficiencies in the UK. Physically active people, those under chronic stress, and anyone who drinks alcohol regularly are particularly at risk because all of these accelerate magnesium depletion.
The signs of low magnesium often overlap with general fatigue symptoms - tiredness, muscle tension, poor sleep quality, low mood, and difficulty concentrating. Which is exactly why it often goes unaddressed.
Oral magnesium supplements are one option, but absorption rates through the digestive system vary significantly. Transdermal magnesium spray - applied directly to the skin - absorbs at 65-85% efficiency and delivers magnesium directly into muscle tissue and the bloodstream without the digestive variable.
What helps: Check your magnesium intake. If you're feeling tired all the time, experiencing muscle cramps, or struggling with sleep quality, low magnesium could be a significant contributing factor. NUYU's Everyday Magnesium Spray is designed for daily use - a simple addition to your morning or evening routine that your body can actually absorb and use.
3. Your Blood Sugar Is Spiking and Crashing
The mid-afternoon energy slump most people experience around 2-3pm isn't inevitable. It's usually a blood sugar crash.
When you eat high-sugar or refined carbohydrate foods - particularly without adequate protein or fat - your blood glucose spikes rapidly and then drops sharply. That drop triggers feelings of extreme fatigue, brain fog, irritability and low energy that can last for hours.
This cycle is one of the most common reasons people feel tired during the day despite a full night's sleep. The fatigue is real - it's just being caused by what you're eating rather than how long you're sleeping.
What helps: Prioritise protein and healthy fats at every meal, avoid eating large refined carbohydrate meals alone, and don't skip breakfast. Stabilising blood sugar is one of the most effective lifestyle changes for boosting energy levels throughout the day.
4. You're Dehydrated - Especially in Winter
This is a well-known cause of fatigue but most people associate it with summer. The reality is that winter dehydration is just as common and significantly underestimated.
In colder months, your thirst sensation decreases even though your body still needs the same amount of fluid. Central heating reduces indoor humidity. We drink less water and more caffeine which accelerates fluid loss. The result is low-grade chronic dehydration that leaves you feeling sluggish, foggy and tired during the day without an obvious explanation.
Even mild dehydration - as little as 1-2% below optimal levels — can impair cognitive function and leave you feeling tired and unable to concentrate.
What helps: Drink enough water consistently throughout the day, not just when you feel thirsty. A practical target is 6-8 glasses of water daily. If you're getting enough sleep and still feel exhausted, drinking enough water consistently is one of the simplest first steps worth taking.
5. Chronic Stress Is Keeping Your Cortisol Elevated
Stress doesn't just affect your mood - it directly affects your energy levels at a hormonal level.
Cortisol is your primary stress hormone. In short bursts it's useful - it sharpens focus and mobilises energy. But chronic stress keeps cortisol elevated for extended periods, which disrupts sleep patterns, accelerates magnesium depletion, impairs recovery, and ultimately leads to the kind of persistent fatigue that feels bone-deep rather than just sleepy.
Many people experiencing fatigue from chronic stress describe it as feeling exhausted but wired - tired during the day, unable to switch off at night. This is a classic sign that cortisol regulation is disrupted.
The fatigue that comes from chronic stress is also self-reinforcing. Poor sleep increases cortisol. Elevated cortisol worsens sleep quality. The cycle continues until something breaks it.
What helps: Addressing the root cause of stress where possible, reducing caffeine intake particularly after midday, magnesium supplementation - which directly supports cortisol regulation - and building a consistent wind-down routine in the evening. Physical activity also helps regulate cortisol, though the timing matters - intense exercise late at night can elevate cortisol further and worsen sleep disturbances.
6. An Underlying Health Condition May Be Causing Your Fatigue
Sometimes fatigue is a symptom of something that needs medical attention rather than a lifestyle fix.
Several health conditions list fatigue as a primary symptom. An underactive thyroid - hypothyroidism - is one of the most common, particularly in women. The thyroid regulates metabolism and when thyroid hormone production drops, everything slows down including your energy levels. Fatigue, weight changes, feeling cold, and low mood are classic hypothyroidism symptoms.
Iron deficiency anaemia is another frequently overlooked cause of fatigue. Without adequate red blood cells to carry oxygen efficiently around the body, persistent tiredness and shortness of breath are common results. Iron deficiency is particularly common in women with heavy periods and in people who follow plant-based diets.
Chronic fatigue syndrome - also known as ME - is a more complex condition characterised by extreme fatigue that doesn't improve with rest and significantly impacts daily functioning. Fatigue syndrome is distinct from ordinary tiredness and requires proper medical assessment.
What helps: If you've addressed sleep, nutrition, hydration and stress and you're still always tired, it may be time for blood tests. A GP can check thyroid function, iron levels, vitamin D, B12 and other markers that commonly cause fatigue when depleted. Talk to your doctor rather than assuming it's just lifestyle - sometimes fatigue is a symptom of a medical condition that needs treatment.
7. You're Not Moving Enough - Or You're Moving Too Much
This one works in both directions.
Physical inactivity is a common cause of fatigue that feels counterintuitive. When you're tired, the last thing you want to do is exercise. But a sedentary lifestyle actually increases feelings of fatigue over time. Regular physical activity improves cardiovascular efficiency, regulates sleep quality, reduces cortisol, and directly boosts your energy levels. Getting enough exercise - even a 20 minute walk daily - makes a measurable difference to daytime energy.
On the other end, overtraining without adequate recovery leads to accumulated fatigue that compounds over time. Athletes and gym-goers who push hard without prioritising recovery - sleep, nutrition, and magnesium replenishment - experience diminishing returns and persistent tiredness that signals the body is not recovering adequately between sessions.
What helps: If you're sedentary, start small - consistent movement is more important than intensity. If you train regularly, treat recovery as seriously as training itself. Magnesium replenishment post-exercise, protein timing, adequate sleep, and rest days are not optional extras - they're the foundation that makes training sustainable.
The Bottom Line on Fatigue
If you're always tired, the answer is rarely one simple fix. It's usually a combination of factors - poor sleep quality, low magnesium, blood sugar instability, dehydration, stress, or an underlying health condition - working together to drain your energy levels.
Start with the basics. Address your sleep habits. Check your magnesium levels. Drink enough water. Manage stress. Get blood tests if symptoms persist.
And if you want a simple daily habit that addresses multiple fatigue causes at once - magnesium supplementation supports energy production, sleep quality, cortisol regulation and muscle recovery simultaneously. It's one of the highest leverage changes you can make when you're feeling tired all the time.
Feeling tired all the time and want to know where to start? Explore NUYU's magnesium sprays at feelnuyu.com - designed for daily use, fast absorption, and real results.
