11 Surprising Reasons Why You're Always Tired

From health conditions to lifestyle habits – the cause of chronic fatigue isn't always obvious.

If you rely on countless cups of coffee to get through the workday, you're not alone.

Exhaustion is par for the course in our culture. One survey found that 76 percent of U.S. respondents feel tired at work many days of the week. Even Google assumes we're all nodding off at our keyboards: Type the query "Why am I..." into the search bar, and it instantly autofills with "so tired".

"Fatigue is a common complaint in my office," said internist Dana Corriel. But late-night Netflix binges aren't necessarily to blame, nor is sleep always the solution. As it's such a general symptom, fatigue could be a result of many illnesses, she said.

Below, health experts break down what could be at the root of your exhaustion, from health conditions to lifestyle factors:

1. You're not sleeping well enough.

It's not just about the quantity of your shut-eye, but also the quality. Insufficient sleep is probably the main cause of feeling tired for Americans, according to Noah Siegel, a sleep-medicine physician at the Massachusetts Eye and Ear Institute at Harvard University.

Seven to eight hours of shut-eye each night is the typical requirement for adults, but even if you're in bed for that amount of time (or longer), you may not be getting the restorative, refreshing sleep you need, he said.

"Many patients come to me saying they're in bed for nine hours, but still wake up sleepy," Siegel said. The culprit? Environmental disturbances, such as blue light from screens, ambient noise, hot or cold temperatures, an uncomfortable mattress, or restless pets or children in the bed are often to blame, he added.

Action plan: There are lots of ways to improve your sleep quality, Siegel said. Try to stick to a consistent sleep schedule, cut out caffeine and alcohol, keep your room cool and avoid screens before bed. For more tips, check out these ways to combat sleep deprivation.

2. You may have sleep apnoea.

Sleep apnoea, a disorder that causes shallow breathing or even pauses in breathing, can disrupt your sleep and affect the quality of your shut-eye. It stems from a partially blocked airway, Siegel said. This could be caused by enlarged tonsils, a small airway, being overweight or allergies.

Action plan: To treat sleep apnoea, you have to open up the airway located in the back of your throat. The most effective way to do so is a medical device called a CPAP, which blows pressured air to keep the airway open, Siegel said. Other options include surgical procedures to remove potential blockages and enlarge the airway, as well as other oral appliances. Losing weight, sleeping on your side and avoiding alcohol may help.

3. Your iron levels are low.

"Low iron levels affect how much oxygen reaches your tissues, and deprives them of the energy they need," Corriel said.

This is often accompanied by anaemia, but patients can still feel tired and have low iron levels without being in the anemic range. Other symptoms of iron deficiency include pale skin, brittle nails and dry skin, headaches and dizziness, chest pain or shortness of breath, cold hands and feet, inflammation or soreness of the tongue, and unusual cravings for ice, dirt or starch, said Madeline Basler, a nutritionist in New York.

Action plan: Eat more iron-rich foods. If you're an omnivore, go for items like oysters, clams, poultry and red meat. Your body absorbs animal sources better than plant sources, Basler said. But vegetarians and vegans can enjoy plant-based foods like white beans, spinach, lentils and fortified cereals.

4. You're deficient in vitamin B12.

"B12 is an essential vitamin found in meat, fish, poultry, eggs and milk," Corriel said. For this reason, some vegetarians – and especially vegans – tend to be deficient in this vitamin. It's necessary for the proper function and development of the brain, nerves, blood cells and other parts of the body.

Action plan: Repletion can be accomplished through various methods, but the most popular ones come in oral or injection forms, Corriel said.

5. You're eating too much sugar.