Why am I always tired? Here are 4 possible causes

Yael Cooperman, MD - Contributor Avatar

Reviewed by Yael Cooperman, MD, Ro, 

Written by Hope Chang, PharmD 

Yael Cooperman, MD - Contributor Avatar

Reviewed by Yael Cooperman, MD, Ro, 

Written by Hope Chang, PharmD 

last updated: Aug 30, 2021

4 min read

Feeling tired is a normal part of everyday life. It’s our body’s way of telling us it’s time to rest and recharge. 

But for some, that warm sleepy feeling that arrives before bed is something they can’t shake even after a full night’s sleep. There is a long list of things that can cause low energy levels and leave you feeling drowsy.

A lack of good sleep, types of medications, and underlying health conditions might contribute to a lack of sleep. We’ll unpack some of the possibilities below. 


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What does being tired all the time mean?

When it comes to being tired, there’s a spectrum. For some people, it means post-lunch fatigue that makes it hard to get through that 1 pm Zoom meeting.

For others, the fatigue is a little more dramatic. It can show up out of nowhere, knocking you out so quickly it would be dangerous to even get behind the wheel of a car.

If you find yourself constantly tired in the middle of the day, you might have a condition called excessive daytime sleepiness. It may be time to consult a healthcare provider if feeling tired interferes with your ability to function on a daily basis. 

If you have reduced physical or mental energy, you might have what's described as fatigue. With fatigue, you likely won't have a problem staying awake, but don’t have the energy you need to get things done throughout the day. 

Why am I tired all the time?

Plenty of things can contribute to daytime sleepiness and fatigue. Here’s a closer look at four of the more common causes of feeling tired. 

Sleep problems

Lack of sleep is one major (and perhaps obvious) contributor to feeling tired.

Even if you think you’re getting enough zzz's, restless sleep or a full night’s sleep with frequent interruptions aren’t going to fill your tank the way a solid eight hours of uninterrupted sleep might.

The Centers for Disease Control and Prevention (CDC) estimates roughly 1 in 3 adults doesn’t get enough sleep at night (Liu, 2014). But how much is enough?

It depends on a lot, but the biggest factor is probably age. While newborn babies spend upwards of 15 hours each day in dreamland, adults typically hover at seven hours per night. Teenagers notoriously need lots of sleep, but as we age, our need for sleep dips a little. People over age 65 require roughly an hour less sleep than those younger than that (Hirshkowitz, 2015).  

For some, busy schedules make it difficult to get enough sleep every night. Others have insomnia and toss and turn for hours trying to fall asleep.

If you have a hard time falling asleep, some tips that might help include going to bed at the same time each night, avoiding caffeine in the afternoon, and steering clear of screens before bed. 

Health conditions

Sometimes fatigue is a symptom of a more serious health issue.

Obstructive sleep apnea (OSA)––where you stop breathing for short bouts in your sleep––can reduce oxygen levels and make sleep ineffective. You might think you’ve gotten a good night’s sleep, but your body isn’t on the same page.

About 1 in 8 people are affected by OSA. It’s more common in men and people with obesity. People with OSA tend to snore loudly and often have headaches in the morning (Young, 2009). 

If you suspect you might have OSA, a healthcare professional might ask you to do a sleep study. This involves sleeping at a clinic or hospital to monitor your breathing overnight.

If you’re diagnosed with OSA, treatment involves sleeping with a breathing assistance machine known as a CPAP, as well as lifestyle changes and sometimes medication.

There are other conditions that can contribute to fatigue, too. Some common causes include:

Mental health conditions

Tiredness can also be a common symptom of mental health disorders like depression, anxiety, and schizophrenia. With schizophrenia, daytime sleepiness and poor quality of sleep are both common (Sharma, 2016).


Drowsiness is a side effect of lots of different drugs. Many allergy drugs available over-the-counter, such as antihistamines like Benadryl (diphenhydramine), are so effective at bringing on the shut-eye, they’re sold as sleep aids.

Other medications that can make you sleepy include: 

  • Opioid pain medications

  • Muscle relaxers

  • Benzodiazepines 

  • Antidepressants

If you take medication that makes you sleepy, consult with a healthcare provider to determine if there’s an alternative option. If there isn’t, you may be able to adjust your dosing schedule and take your meds at night, which may prevent daytime sleepiness.

When is it time to see a doctor?

As you can see, many things lead to fatigue and daytime sleepiness. If you’re unsure of the cause, you don’t have to figure it out on your own. 

If exhaustion affects your ability to stay awake while driving, at work or school, or during daily activities, it’s a good idea to schedule an appointment with a healthcare professional. 

Blood tests and a review of your medications may pinpoint the source. Information that can be helpful to jot down while sorting out issues related to fatigue include: 

  • When you started feeling tired or how long you’ve been feeling this way

  • If anything has recently changed in your personal life, work schedule, or diet

  • Any new medications you’re taking

  • Sleep habits, including how much sleep you typically get a night. Keep in mind, if you’re tired because you’re not leaving enough time for sleep every night, there’s not much a provider can do for you

As there are many potential causes for tiredness, finding your specific source requires time and patience. Providing accurate and thorough answers during your visit will give a healthcare provider an excellent starting point.


If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.

  • Chervin, R. D. (2021) Approach to the patient with excessive daytime sleepiness. Retrieved July 28, 2021 from https://www.uptodate.com/contents/approach-to-the-patient-with-excessive-daytime-sleepiness#H19110187

  • ​​Hirshkowitz, M., Whiton, K., Albert, S. M., Alessi, C., Bruni, O., DonCarlos, L., … Adams Hillard, P. J. (2015). National Sleep Foundation’s sleep time duration recommendations: methodology and results summary. Sleep Health, 1 (1), 40–43. doi: 10.1016/j.sleh.2014.12.010. Retrieved from https://pubmed.ncbi.nlm.nih.gov/29073398/

  • Liu, Y., Wheaton, A. G., Chapman, D. P., Cunningham, T. J., Lu, H., & Croft, J B. (2016). Prevalence of Healthy Sleep Duration among Adults—United States, 2014. MMWR Morbidity and Mortality Weekly Report, 65, 137–141. doi: 10.15585/mmwr.mm6506a1. Retrieved from https://www.cdc.gov/mmwr/volumes/65/wr/mm6506a1.htm

  • Sharma, P., Dikshit, R., Shah, N., Karia, S., & De Sousa, A. (2016). Excessive Daytime Sleepiness in Schizophrenia: A Naturalistic Clinical Study. Journal of Clinical and Diagnostic Research, 10 (10), VC06–VC08. doi: 10.7860/JCDR/2016/21272.8627. Retrieved from https://pubmed.ncbi.nlm.nih.gov/27891431/

  • Young, T., Palta, M., Dempsey, J., Peppard, P. E., Nieto, F. J., & Hla, K. M. (2009). Burden of sleep apnea: rationale, design, and major findings of the Wisconsin Sleep Cohort study. WMJ: Wisconsin Medical Journal, 108 (5), 246–249. Retrieved from https://pubmed.ncbi.nlm.nih.gov/19743755/

How we reviewed this article

Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

Current version

August 30, 2021

Written by

Hope Chang, PharmD

Fact checked by

Yael Cooperman, MD

About the medical reviewer

Yael Cooperman is a physician and works as a Senior Manager, Medical Content & Education at Ro.