11 Reasons You're Tired All the Time*

Reviewed by Jenna Gress Smith, PhD, and Sohaib Imtiaz, MD, MPH

Here at Zest, we believe sleep is the foundation for optimal health and wellbeing. A robust body of research shows, and we can attest, that our mental, physical, and emotional health suffer when we don’t get enough good-quality rest.

But there can be other reasons for feeling tired during the day – fatigued, actually, and we’ll get into the terminology in a moment – that are not directly due to sleep deprivation, though they may impact your sleep.

The first, obviously, is stress. Excessive, prolonged stress can leave you depleted and drained, physically and emotionally. Besides interfering with the quality of your sleep, it can lead to changes in the serum levels of many hormones, triggering or worsening endocrine disorders of the adrenals or thyroid, which can cause fatigue.

But there are other reasons for tiredness that you might not be aware of.

Sleepy, tired, or fatigued?

Although the words tired, fatigued, even sleepy are often used interchangeably, they’re technically not the same thing, says Jenna Gress Smith, PhD, sleep specialist. “Sleepiness occurs naturally in the evening, brought on in part by a buildup in the brain of the neurotransmitter adenosine. We know we’re sleepy when our eyes get heavy, or we start to nod off and cannot stay awake — it’s more of a physiological sensation.”

Tired could be how you feel after a hectic day or a hard workout.

Fatigue, on the other hand, is when you’d describe yourself as “always tired,” even after what you thought was a good night’s sleep. “It’s a lingering feeling of being worn out, run down, no energy, no focus or motivation to complete tasks,” says Dr. Gress.

Whichever word you use — and we admit to using them all — think about those differences in terms of describing how you feel.

Here are 11 reasons you may feel tired that are not directly caused by sleep deprivation, but which can impact your sleep.

1. You eat a lot of processed foods

According to Levels Health, processed foods that are high in sugar, salt, and unhealthy fats, along with flavoring, food coloring, food derivatives and synthetic additives (i.e., ingredients you can’t pronounce that are not found in nature) make up the majority of calories in most Americans’ diets. Common additives and preservatives such as inorganic phosphate, monosodium glutamate, as well as artificial flavors and sweeteners can disrupt the gut microbiome and trigger negative reactions in the body that can make you tired. Because highly processed foods are low in fiber and healthy fats, they’re quickly digested, causing spikes and crashes in blood sugar, which will zap your energy.

“A steady diet of only processed foods can lead to nutritional deficiencies,” says Sohaib Imtiaz, MD, MPH, who is board certified in lifestyle medicine. Insufficient iron, B12, and folate levels will result in fatigue as your body needs these nutrients for energy metabolism. “Fatigue is one of the biggest symptoms of a vitamin D deficiency,” Dr. Imtiaz says. “Many people are vitamin D deficient especially if they live in colder climates.”

The remedy for warding off diet-related fatigue is fairly simple: "Eat more whole foods: green veggies, lean meat, fish, eggs, nuts, fresh fruit, and whole grains. And/or take a vitamin D supplement."

2. Inflammation

Inflammation is supposed to occur as your body’s first line of defense against infections and injuries. But it can wreak havoc on your body when what should be an acute response becomes a low-grade chronic condition. Certain diseases such as autoimmune disorders, cancer, or type 2 diabetes cause chronic inflammation, “but so can lifestyle factors like smoking, being overweight, chronic, unmanaged stress, or an excess of alcohol,” says Dr. Gress. Studies show that people with chronic, low-grade inflammation can experience persistent fatigue.

The development of fatigue is complex and not fully understood—except for the fact that low-grade chronic inflammation plays a key role. One possible cause may be oxidative stress, which refers to an imbalance with increased production of free radicals compared to the compensatory mechanisms that inhibit or repair the damage that may occur. Molecular mechanisms that protect against cellular stresses may be “fatigue generators” that act on the brain through pathways that remain unknown.

Some signs and symptoms of chronic inflammation are poor digestion (bloating, abdominal pain, constipation, diarrhea, which may be caused by a bacteria imbalance in the gut); pain or swelling in the joints; swollen lymph nodes; low grade fever; or rashes.

Some ways to lower inflammation include eating an anti-inflammatory diet of whole grains high in fiber, polyphenol-rich foods, and healthy fats including fatty fish, avocado, and nut butters; stress reduction strategies like meditation or journaling; appropriate physical exercise; and, yes, getting good sleep.

3. Dehydration

All the systems in your body need water to function properly—every cell, tissue, and organ. Water lubricates joints and regulates body temperature. It’s crucial for proper digestion for fuel and energy. Staying hydrated helps your heart pump blood more effectively, and transport oxygen and other essential nutrients to your cells.

When you're dehydrated you may feel like you're losing steam throughout the day. You’ll feel logy, sluggish, fatigued—just like how you feel when you’re sleep deprived. Research also shows that dehydration can negatively affect your sleep by impacting your natural circadian rhythm. It’s a two-way street.

The National Academy of Medicine suggests about 13 cups and 9 cups of water daily for healthy men and women respectively, with 1 cup equaling 8 ounces, and more if you’re physically active or in a hot climate.

4. Depression

Being fatigued doesn’t mean you’re depressed, but fatigue can be a symptom of depression. “Depression is a complex condition with many possible and interlinked causes, including genetics, medical conditions, stressful life events, and brain chemistry,” says Dr. Gress. “And it can be challenging to tell the difference between everyday tiredness and depression-related fatigue.”

Depression is linked to changes in brain neurotransmitters such as dopamine, norepinephrine, and serotonin, which help regulate energy levels, sleep, appetite, motivation, and pleasure. “When someone is depressed, their energy level dips, and they're less motivated to engage in meaningful social activities," says Dr. Gress. That can worsen feelings of loneliness and sadness. People often get caught in a vicious cycle of feeling down, which leads to a lack of energy and motivation, which leads them to withdraw from meaningful activities and feel more tired, etc etc.”

There are many reasons we feel tired, but you’re also experiencing feelings of persistent sadness, hopelessness, helplessness, or suicidal thoughts, seek medical advice to see if you have a depressive disorder.

5. Anxiety

Anxiety is a feeling of fear, dread, or apprehension about a particular event, or how you think about an event. You might feel drained after a bout of anxiety, and usually a good night’s sleep will restore your energy levels.

Some people experience anxiety even when there’s no obvious trigger. When feeling anxious becomes chronic and long term— “meaning someone has an anxiety reaction to most situations rather than as a one-time response to a specific stressor" — it’s often accompanied by a feeling of exhaustion, says Dr. Gress.

Anxiety causes your brain to release a flood of hormones to prepare you to fight, flee, or freeze. In response, you might feel a quickened heart rate, chest pain, dizziness, or dry mouth. "Though the crash that follows may be temporary, the feeling of exhaustion can persist even after you've gotten some rest. Chronic anxiety and fatigue go hand in hand.”

Anxiety and anxiety disorders are often associated with worry and nervousness, which can also lead to sleep disturbances. If you are experiencing persistent anxiety it’s a good idea to speak with your doctor.

6. Medication side effects

While prescription medications can be lifesavers, “many have side effects, one of which may be fatigue,” says Dr. Imtiaz. “Medications like antidepressants, anti-anxiety medications, pain killers, and medications to treat ADHD can make you tired or contribute to poor sleep, which may make it hard to feel well-rested. In order to combat this make sure you regularly check in with your doctor as well as get your blood tests checked."

7. Too little (or too much) exercise

One big reason for feeling sluggish is a lack of exercise. Exercising regularly increases blood flow and improves circulation; generally speaking, the more active you are the more energy you’ll have throughout the day. Too little exercise can cause deconditioning, making it harder and more tiring to perform daily physical tasks.

Movement also stimulates our brain to produce endorphins, those “feel good” chemicals, says Dr. Gress.

If the weather is nice, take your workout outdoors for some sunshine and vitamin D, which can help boost your energy level. Regular exercise has also been shown to improve sleep.

If you work out regularly, well done! Just remember to figure in recovery days to your schedule, as overtraining can put too much stress on the joints, muscles, and bones and cause fatigue—or injury. When it comes to recovery there’s no one size fits all—the amount of time you need depends on the intensity of your training, the type of exercise you’re doing, and you. After a HIIT session, you’ll probably want to skip a day before your next workout; if you’re doing a full body weight workout, 24 to 48 hours is recommended. (A good rule of thumb is to give yourself 24 to 48 hours to rest before hitting any of the same muscle groups.) For light to moderate cardio, you can probably work out every day as long as you’re not feeling wiped out.

8. Medical conditions such as thyroid disease or type 2 diabetes

The thyroid, a small, butterfly-shaped gland at the base of your neck, produces several hormones that affect all aspects of your metabolism. Thyroid disease is a general term for a medical condition that keeps your thyroid from making the right amount of those hormones. When the thyroid makes too much thyroid hormone (called hyperthyroidism), your body uses energy too quickly; that can cause a quickened heartbeat, weight loss, even feelings of nervousness, and can make you tired. If your thyroid makes too little thyroid hormone (called hypothyroidism) you can feel tired, sluggish, and you may gain weight. Either way, an imbalance in thyroid hormones can cause fatigue.

Thyroid disease is fairly common and can affect anyone of any age, though more women than men tend to have it. Your doctor can properly diagnose you through bloodwork.

“Fatigue is often a symptom associated with type 2 diabetes,” says Dr. Imtiaz. “There are many possible causes, including everything from diabetes related complications to underlying conditions. The most common cause is uncontrolled blood glucose. With type 2 diabetes, poor blood sugar control typically results in hyperglycemia or high blood sugar, which can cause fatigue among other symptoms.”

9. Low testosterone

For some men, low testosterone can be the reason for fatigue that doesn't improve with rest. According to clevelandclinic.org close to 40% of men aged 45 and older have low testosterone levels. If you're also experiencing mood changes, sexual dysfunction, or weight gain, it's probably worth scheduling an appointment with your PCP.

10. Constipation

Constipation and fatigue frequently occur together. How often you poop can vary from person to person, but generally speaking, you’re considered to have constipation if you go less than three times per week. Dehydration, a low-fiber diet or other nutritional issues, and certain medications and medical conditions can cause constipation as well as fatigue. If either is ongoing, speak with your doctor to determine the cause.

11. Too much caffeine

Caffeine is, of course, a stimulant, but consuming too much can backfire for a couple of reasons. First, you can build up a tolerance, which means you’re not feeling that energy buzz you used to get after a single Americano. Second, caffeine is a diuretic, which can leave you dehydrated (and tired, see No. 3) if you consume too much. Third, when caffeine enters the brain it adheres to the brain’s adenosine receptors, “blocking the adenosine, which is what helps us feel sleepy," says Dr. Gress. But just because our brain isn't processing the adenosine doesn’t mean it's not producing it. When the caffeine wears off, you’re left with an adenosine buildup, which can leave you feeling drained, and even more tired than your afternoon coffee. “That’s why it’s important to keep your daily caffeine intake to less than 400 mg and stop drinking it 8 to 10 hours before bedtime,” Dr. Gress says.

Lastly, if you’re adding sweetener to your coffee, you’re priming yourself for a sugar crash. Blood sugar spikes and crashes are a fast route to fatigue.