Updated at 11.09.2025•6 Min. Reading time

Problems with fatigue? The 7 most common causes

You constantly feel tired and sluggish, even though you have actually slept enough. You have not turned night into day, yet you have a constant companion: the persistent tiredness. Our sleep only influences to a small extent how tired we feel. Tiredness actually has many different causes. But what helps against constant tiredness and how can we feel less tired and sluggish?

Constantly tired and sluggish? - The meaning of fatigue in the body

If you constantly feel tired and sluggish, your body is trying to tell you something. Therefore, fatigue should be understood as a kind of signal that our body sends us. This signal is meant to draw our attention to the fact that something is missing in our body: sleep, exercise, nutrients, fluids, or simply rest. If you are always tired, these could all be the causes.

In addition to tiredness, if other symptoms such as weakness, lack of drive, or problems with performance/concentration occur, you should listen to your body. These are signs that should be taken seriously and may go beyond "normal" tiredness caused by, for example, lack of sleep.

Typical symptoms of fatigue can include:

Frequent yawning
Sleepy feeling
Increased effort or feeling of weakness
Reduced performance
Decreased ability to concentrate
Burning eyes, eye floaters, brief blackouts in front of the eyes.

Fatigue & Sleep: How are they related?

Many probably know it: You have actually slept enough, yet you still feel tired and sluggish after waking up. Then you rightly ask yourself: "Why am I so tired?"

The tiredness during the day is indeed related to our sleep. It's not so much about the quantity of sleep, but rather about the quality of sleep, meaning how quickly we fall asleep and how well we stay asleep. The number of hours plays only a minor role. The amount of sleep a person needs is very individual anyway. Some feel well-rested with 5 or 6 hours, while others need 9 or 10 hours. Often, 7 to 9 hours of sleep are recommended for adults. On the other hand, children and teenagers need much more sleep and would otherwise often feel tired.

Perpetually tired in spring: The so-called spring fatigue

Almost everyone has probably heard of the so-called spring fatigue before, but what does it actually mean? In Germany, around 50% of people are affected by it between March and May. If you suffer from spring fatigue, you are constantly tired, exhausted, lacking energy and often complain about a performance and mood low¹. Although nature is blooming and slowly coming back to life, you feel rather the opposite and are literally stuck in hibernation.

As the name suggests, this particular form of fatigue is related to the season and the changes our bodies undergo during this time. The light and weather conditions change, affecting our hormone balance. For example, instead of melatonin in the spring, serotonin is now increasingly released after winter. If unhealthy eating habits are added to the mix, we run the risk of our body lacking important nutrients such as vitamins during this adjustment phase. In general, it is possible that our body is very busy adapting from winter to summer, and as a result, we may struggle with fatigue.

Why am I always tired? - 7 causes of fatigue

Constantly tired? Fatigue can have various causes. The constant tiredness seems to have become a daily companion, but it doesn't have to be! We explain 7 possible causes and show what can help. Often, it is due to small things like lack of exercise, dehydration, unhealthy eating, or stress.

Constant tiredness due to lack of exercise

Too much movement, such as after a strenuous day of hiking in the mountains, can make you tired. But too little movement can also have the same effect. This is because when we don't move enough, our body doesn't get properly activated. This means that circulation, blood flow, and metabolism are not sufficiently stimulated, and our joints and muscles are not challenged enough. So, someone who spends the whole day on the couch can feel just as tired and exhausted like someone after an active day. The main cause of constant fatigue here is lack of exercise.

Tired and sluggish after a rich meal

Unhealthy and sometimes greasy food can make us tired and sluggish. Especially at lunchtime, after eating, many people experience: a midday low. This becomes particularly noticeable when instead of salad, we have eaten a burger, a schnitzel with fries, or a roast pork. These rich, high-calorie dishes can cause severe fatigue after eating. This results in what is commonly known as the 2 p.m. slump. This is because the stomach requires a lot of blood for digestion, which then is lacking in other parts of the body.

Always tired and sluggish? - Possible cause: a deficiency of nutrients and vitamins

„Fatigue can be a sign that the body is lacking something.“

Dunja Rieber,
Nutrition scientist

Vitamins for fatigue? It is scientifically proven: The micronutrients folic acid, vitamin C, B2, B6, magnesium, and iron help reduce tiredness and fatigue. Iron, magnesium, vitamin B6, and B12 also support energy metabolism. Through a nutrient-rich diet, our body can absorb these and other vitamins and minerals. Therefore, it is important to eat a varied diet and include portions of fruits and vegetables daily.

It is not possible to give a general answer as to exactly what deficiency is causing fatigue. Also, the question "Which vitamin is lacking in the body when feeling tired?" cannot be answered with just one response, as different micronutrients often require and complement each other. For example, vitamin C promotes the absorption of iron.

Constantly tired due to not drinking enough

If you feel tired all day long, one cause could be dehydration. Simply not drinking enough water can lead to the blood becoming thicker and circulating more slowly in the body. As a result, the brain receives less oxygen. The outcome is similar to unhealthy eating habits. If you feel tired during the day, often thirsty, or have a dry mouth, the advice is to drink 1.5 to 2 liters of water, unsweetened teas, etc.

Constantly tired and lacking energy due to too much stress - Can fatigue be caused by the mind?

Physical and mental stress increases the need for nutrients. On the other hand, stress can also lead us to eat unhealthier by consuming more sugary and fatty snacks as well as ready-made meals that provide us with few vital nutrients. If the body lacks important nutrients, we end up eating unhealthily in the long run, and when we are stressed, we feel quickly exhausted, tired and lacking in energy.

Bad air makes you tired

If you do not regularly ventilate and exchange the used air for fresh air, the body often reacts with fatigue, weakness, and lack of drive. This is due to the high level of carbon dioxide in the air. It makes you feel weak and tired. That's why regular ventilation is very important to maintain full performance and concentration.

Persistent fatigue: When should you see a doctor?

Being tired every now and then is something that everyone knows. Only if persistent fatigue (chronic fatigue) lasts for several weeks, you should consult a doctor. The cause should be identified as soon as possible. However, you should not immediately assume the worst when feeling tired, as there can be many reasons behind it.