What If It Is Not Your Sleep? Exploring Other Causes Of Daytime Fatigue

There can be many causes of daytime tiredness or fatigue. Identify each of the reasons that may be contributing to your condition. Then set about making some changes to see if you can feel better.
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By Brandon R. Peters, MD

When sleep is not refreshing, the feelings of tiredness and fatigue can undermine your daytime function. Beyond common sleep disorders like obstructive sleep apnea and insomnia, what are some of the reasons for feeling tired? Explore some of these potential causes, ranging from medications to diet and exercise, and try to discover what you can do to feel better.

Understanding the Role of Sleep Disorders

First, it is important to recognize that there is a difference between sleepiness and fatigue. Sleepiness is the strong desire for sleep that often immediately precedes falling asleep. It is sometimes called drowsiness. Sleepiness is due to the build up of a chemical in the brain called adenosine that enhances the ability to fall and stay asleep (1). In contrast, fatigue is a sense of tiredness, exhaustion, and low energy. People often describe a sense of heaviness, a lack of initiative, and an inability to do normal daytime activities without a sense of impairment.

Sleep disorders often contribute to feelings of sleepiness and fatigue. The most common cause is simply getting too little sleep to meet basic sleep needs. Sleepiness can also be due to poor sleep quality, such as occurs in obstructive sleep apnea or narcolepsy. Fatigue is more commonly associated with insomnia. Sometimes we focus too heavily on our sleep when trying to discover the reasons for feeling tired.

Considering Other Causes of Daytime Fatigue

It can be important to be assessed if you have symptoms suggestive of a sleep disorder, but focusing solely on sleep as the cause of feeling badly during the day may put more pressure on you to sleep. This can be especially problematic in insomnia. Instead, consider some of the other reasons why we may feel tired during the day. By tacking these issues, if they are relevant to your situation, you may make improvements that can be very helpful.

  • Mood Problems

Mood and sleep walk hand in hand, each one significantly affecting the other. Depression can commonly be associated not only with feeling down, but having a sense of entrenched fatigue (2). A lack of initiative, called apathy, may manifest in various ways. Anxiety can also contribute to daytime dysfunction. Both conditions are commonly associated with insomnia. Bad moods may leave you feeling grouchy, irritable, and tense. Stress may similarly undermine how rested you feel during the day.

  • Diet

It is possible for what you eat to contribute to feelings of feeling lethargic, bloated, and tired during the day. Though conditions like celiac disease are relatively uncommon, various sensitivities or food allergies are more widely recognized (3). Lighter fare, including less processed foods and more fruits and vegetables, may help you to feel better during the day. Consider keeping a food journal to see if you can identify certain foods that worsen how you feel after eating.

There are certain foods like turkey that contain higher levels of tryptophan, an amino acid associated with daytime sleepiness. In addition, some foods like cherries contain low levels of melatonin (4). These are unlikely to be significant contributors to feeling tired.

Ensure that you are drinking enough water. It may be helpful to keep a water bottle at hand to encourage consistent consumption throughout the day. Although the amount of water needed varies, you should certainly avoid feeling thirsty during the day. If you urinate infrequently, with highly concentrated urine, you may need to drink more. Prioritize water over other fluids that might add unneeded calories.

Finally, consider the role of caffeine in how you are feeling. Though caffeine is a stimulant that initially wakes us, as it wears off (typically over 4-6 hours), we may experience a "caffeine crash" that leaves us feeling sleepy (5). This may be especially profound in mid-afternoon.

  • Exercise

Have you ever noticed how well you sleep after a particularly busy or physically active day? Exercise can have an impact in how you feel during the day and how well you sleep at night. Though it was previously recommended that exercise be avoided just prior to bedtime, it is important to work in the workouts when you can. Doing too little during the day, or conversely doing too much, leave you feeling fatigued and tired. Try to find the right balance. In particular, try to find activities that you enjoy. Walking, bicycle rides, and swimming are great aerobic exercise. Try to get 30 to 60 minutes of exercise every day, but don't beat yourself up if you miss a day. Maintain a healthy body weight and avoid being out of shape, overweight, and obese. Mood can follow movement, so get yourself moving.

  • Infections

Although you would be expected to have other signs or symptoms of an infection, it is possible that the problem may be smoldering under the surface. Urinary tract infections (UTIs) more commonly impact women. If you have a cough with fever, you might think about a pneumonia. Yeast infections, including being afflicted with Candida albicans, may also have a role (6). If you simply aren't feeling well, consider getting checked out by your primary care provider.

  • Medical Problems

There are other common medical problems that can leave you feeling tired. Chronic pain, especially when it requires the use of daily pain medications, can affect how you feel during the day. Constipation may contribute to feeling bloated and uncomfortable. Low blood iron levels, such as occur in association with iron-deficiency anemia, also can leave you feeling drained. Hypothyroidism is also extremely common and contributes to feeling tired and fatigued. There are other serious conditions that might also, less often, contribute to fatigue (7).

  • Medications

When reviewing the role of medical conditions, don't forget about the impacts of medications. Whether prescription, over-the-counter, or supplements, these medicines can have important side effects that should not be overlooked. Review your medications' lists of side effects. Medications that act on the central nervous system (like antidepressants) frequently contribute to fatigue. In addition, certain cardiac medications (like beta blockers for high blood pressure) can be problematic. Over-the-counter antihistamines, such as those that contain diphenhydramine, frequently cause daytime sleepiness. When reviewing your supplements, consider the contribution of any that contain serotonin, tryptophan, melatonin, or valerian root. Consider the timing of your fatigue in relation to the initiation of any of these drugs, and speak with your doctor before discontinuing any prescribed therapy.

  • Other Causes

There are other things that can contribute to feeling tired or fatigued during the day. After lunch, consider the role of the natural dip in the circadian rhythm that occurs between 1 PM and 3 PM. Everyone feels a little sleepy at this time, and this feeling will be more intense if you get poor quality or inadequate sleep at night.

If you spend too much time lounging about in bed, or on the couch, you may also feel more tired. Try to spend no more than 8 to 9 hours resting during a 24-hour period. Consider your own sleep needs when you are feeling well and aim to sleep this amount by setting an alarm and getting morning sunlight upon awakening. For those with physical ailments or restrictions, even sitting up in a chair can be helpful. As much as possible, try to maintain normal activities, including household chores and getting out to run errands and to socialize.

Boredom itself may exacerbate fatigue. You may feel like you have nothing better to do than to sleep. This restricted life may impact your mood and productivity.

Finally, some people mistake their eye fatigue for physical fatigue. Staring at computer screens or television for a prolonged period may exacerbate these problems. If your eyes feel fatigued (with associated blurring of the vision or twitching of the eyelids), try to take a break to get some relief.

There can be many causes of daytime tiredness or fatigue. Identify each of the reasons that may be contributing to your condition. Then set about making some changes to see if you can feel better. If you continue to struggle, don't hesitate to seek extra help and get evaluated by a sleep specialist.


1. Clinton JM, Davis CJ, Zielinski MR, Jewett KA, Krueger JM. Biochemical regulation of sleep and sleep biomarkers. J Clin Sleep Med. 2011 Oct 15;7(5 Suppl):S38-42.

2. Wright J, O'Connor KM. Fatigue. Med Clin North Am. 2014 May;98(3):597-608.

3. Pinto-Sánchez MI, Bercik P, Verdu EF, Bai JC. Extraintestinal manifestations of celiac disease. Dig Dis. 2015;33(2):147-54.

4. McCune LM, Kubota C, Stendell-Hollis NR, Thomson CA. Cherries and health: a review. Crit Rev Food Sci Nutr. 2011 Jan;51(1):1-12.

5. Magkos F, Kavouras SA. Caffeine use in sports, pharmacokinetics in man, and cellular mechanisms of action. Crit Rev Food Sci Nutr. 2005;45(7-8):535-62.

7. Mayo Clinic Staff. Fatigue Causes. Last accessed: June 27, 2016.

Brandon R. Peters, MD, is the writer on sleep for Verywell.com, a neurology-trained sleep medicine specialist at Pulmonary and Sleep Associates of Marin in Novato, Calif., and consulting assistant professor at the Stanford Center for Sleep Sciences and Medicine. This Center is the birthplace of sleep medicine and includes research, clinical, and educational programs that have advanced the field and improved patient care for decades. To learn more, visit us at: sleep.stanford.edu.