7 Legit Medical Reasons You Feel Exhausted

And how to feel less so!

Why Do I Feel Like CRAP?! Doctor Exhausted Man Repeller-Feature

If staying in is the new going out, then why are so many of my patients telling me they are flat-out exhausted? Every day I hear this complaint from 20, 30 and 40 year olds in the prime of their lives.

Their body aches. They can hardly keep their eyes open at their desks. They can’t concentrate. They’re almost sheepish when they admit it, because who wants to admit to their doctor that they are sleepy, much less ask for help for it?

The truth is that most of these patients are exhausted by life — by an endlessly stressful news cycle, next-level career ambitions and an addiction to screens — and that exhaustion can lead to more severe chronic diseases if left untreated.

Here are the seven of the most common reasons you may be feeling exhausted and spent. If any of this sounds familiar, then you should probably see a doctor and get tested. It’s not normal or pleasant to be permanently wiped out.


You could have an iron deficiency.
If you get your period regularly and don’t eat enough meat or take an iron supplement, you could be anemic, meaning you have too few red blood cells to carry oxygen around your body — making simple tasks like climbing a flight of stairs seems unreasonably hard. A simple blood test from your doctor can rule this out!

You’re out of shape.
We live ridiculously sedentary lifestyles. The average person spends 11+ hours a day in front of a screen. Tech was supposed to give us more freedom, but instead it’s the new ball and chain. If you sit all day and only spend a few minutes a few times each week working out, you may be what’s known as “deconditioned,” meaning your muscles fatigue easily.

You’re too in shape.
Overdoing what I call “long-haul cardio” (running and spinning in particular, but really all forms of overexercise), leaves people depleted, dehydrated and deflated. If you find yourself relying on coffee and sugar-bomb fruit smoothies to keep your energy up and are working out hard six days a week, you could be sapping your reserves. This contributes to adrenal fatigue, which results from spending too much time in “fight or flight” mode where cortisol and adrenaline are high. Your body never has a chance to recover.

You’re getting low-quality sleep.
Maybe you’re in bed for seven hours, but thanks to the blue light emanating from your laptop and those 30 minutes spent scrolling Insta when you get into bed, your circadian rhythm is disrupted, your cortisol is high at when it should be low and you’re tossing and turning, not hitting the ideal three or four full REM cycles per night that we need to feel rested.

It could be your thyroid.
What is that? It’s a gland in your neck that drives your metabolic rate and governs things like digestion, weight, energy and mood. One in eight women in the U.S. will be diagnosed with a thyroid problem in her lifetime and many are undiagnosed. At Parsley Health, the most common reasons we see thyroid dysfunction are nutrient deficiencies, gluten sensitivity and inflammation resulting from a high-carb/high-sugar diet. Autoimmune conditions are also a major reason; doctors often don’t test for the antibodies to find it. We test all patients’ thyroids routinely because it is such a common problem.


It could be depression.
“I’m tired” has become polite code for “I’m in a bad mood.” If you feel irritable, anxious and down most of the time, you could be suffering from low-grade depression — known in doctor-speak as “dysthymia.” You may feel this way because your body is inflamed from eating too much sugar and processed food, because you’re low on key nutrients like B vitamins and magnesium or because you’re chronically not getting enough sleep. When you address these issues, the symptoms of depression and anxiety often get significantly better or disappear.

You may have a vitamin D deficiency.
Over 80% of our patients at Parsley Health are vitamin D deficient because most don’t spend enough time in the sun — even in California! Vitamin D is a hormone, not just a vitamin. It’s available in fatty foods like cod-liver oil, and your body makes it when you are exposed to sunlight. Vitamin D is crucial for bone health and calcium absorption, but also regulates the immune system. If you’re getting too many colds and sinus infections, leaving you feeling run-down, start boosting your intake of vitamin D. We recommend supplementing 5000IU with vitamin D3/K2 drops if you know you are low, and 2000IU for anyone even if you haven’t been tested.

Graphic and illustrations by Maria Jia Ling Pitt.

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  • Grace B

    I got blood work done last summer, found out I was anemic, started taking iron supplements. I ran out in October, didn’t think anything of it and just last week decided to try taking them again (I know, a dr didn’t tell me to…) and holy cow, GAME CHANGER. I’m currently working the night shift and it has made me completely bitchy but thanks to these iron pills (Now Foods brand) I feel like so so much better. And I actually have the energy to take my new dogs on walks! Now to work on the sendentariness…

  • streats

    Probably most of these are very likely for me, tbh. I don’t eat meat at home, and only occasionally when I’m out, I don’t work out (though I walk everywhere) and work in a sedentary profession, coffee is generally the only fluid I drink, I sleep little and poorly, I have a history of depression, and I live in Ireland (so very little natural vitamin D). My blood work has always shown low-but-within-normal iron levels, and my doctor legit told me to just drink more Guinness (Ireland y’all; they used to prescribe it to pregnant women for their iron levels). I wonder which would be the most effective to tackle first – although obviously all of them would be ideal to “fix” or improve/manage.

    • Katrina Elizabeth

      I just Googled the Guiness-iron thing. Am so impressed!

    • devilwearsnada

      I’d start by hydrating with clean water (80 oz per day minimum) and taking vitamin D.

  • Allie Reese

    I get low quality sleep because of narcolepsy, so that’s a thing also. (Not the kind of narcolepsy where someone laughs and falls asleep instantly, but is just tired all the time. Google it!)

  • Adrianna

    I recommend adding nutritional yeast to your food. I’ve been experimenting with different nutritional supplements or “superfoods,” and I can say with full confidence that I feel an immediate difference after eating nutritional yeast. (Particularly melted into soup.) It’s not like caffeine or a sugar high, but a jolt of clarity.

  • JB

    Love this. Such good advice. I’ve experienced this exhaustion on and off throughout my life. Especially when I was in my twenties. At some point, I had a year where I wasn’t sleeping well at all and I felt completely depleted. It took quite a while and a lot of experimentation to finally figure out how to re-center myself. I had to adjust what I was eating (take vitamins!), exercise differently (less intense cardio and more yoga, strength training) and try to develop good sleep habits. A lot of trail and error. Now, when I recognize that I’m slipping into that familiar fatigue, I readjust and incorporate what I’ve learned to re-calibrate. It’s quite overwhelming trying to figure out what your body and soul needs to be at its best!! I’m sure that’ll change as I get older as well…an ongoing process for sure.

    • Mariana

      I can’t seem to find a conscience about taking or not taking vitamins. Some say is essential, some say it only makes your pee expensive.

      • JB

        Lol. Most do make your pee yellow! I’m always of the opinion that “it doesn’t hurt to try.” Why don’t you try it for a couple months and see how you feel? If you feel like you’re taking snake oil, move on and stick to a nutritious diet. 🙂

        • Mariana

          Sometimes I do some magnesium capsules because my mother made us take them as kids. They are good when you are tired and anxious. I don’t see major changes but I guess it doesn’t hurt. But I would like to take a multivitamin or something more global to help boost my health.

          The last time I asked a physician about vitamins (like 1 month ago) and if they would make a difference she told me “Well, if you bought it don’t waste, but if you have a nutritious diet is enough”.

      • Olivia

        I really never believed in taking vitamins, but started taking a multivitamin about a year ago and haven’t been sick since! Normally I get sick 2-3 times per year. I highly recommend!

      • devilwearsnada

        TAKE VITAMINS!! but research them (or have a legitimate doctor make recommendations) and make sure you purchase quality brands. One of the misnomers of vitamins is that they are all created equal (they aren’t) and many of them don’t have all the “ingredients” that are necessary to improve your actual health. Don’t get conned paying extra for bad brands.

        I have been working with a naturopathologist since October and since I’ve been on a consistent vitamin regiment I haven’t been ill. Since I started taking Vitamin D both my energy and my mood has improved.

        This is a pretty comprehensive list MR. Thank you for providing this information!

  • ihaveacooch

    i’m convinced my office job/long commute are working together to slowly kill me. i work out several times a week and try to walk a ton on the weekends but sitting for hours at a time monday-friday has serious ramifications over time.

    • Katrina Elizabeth

      I second that. When I went back to university for design, the long hours at a computer completely changed my body in the worst way. Then came freelance, then came an office job… nothing but sitting. Once I graduate, I know I need to seriously reevaluate how I go about working before the damage is irreversible. Sitting truly is the new smoking.

      • ihaveacooch

        it’s terrible for you! i want to get a standing desk but i don’t work in one of those “hip” offices where it would be a standard thing.

        • Katrina Elizabeth

          Standing desks are great but I think there is some misinformation around them. They’re not a total solution for sitting because some people just end up standing for way too long, which has equally detrimental effects to sitting. The key is to take frequent breaks, alternate between sitting and standing and move often. Easier said than done, though!

        • Pau

          I have to stand my entire shift… it’s a whole different type of draining. Seems like there’s no winning. 🙁

    • The commute plus the office job were draining my life too! so I actually made the decision to move closer to work, and now I can actually walk to the office. Since getting a dog, I am also forced to walk/run with him twice a day. At least that life-draining part of my life is gone!

  • Kristin

    This is a little pseudo-mediciney. Adrenal fatigue. Vitamin deficiency—particularly vitamin d—low levels are linked to many conditions but it isn’t even agreed what is low, and supplementation has not been shown to help anything except fall prevention in the elderly. Also there is no evidence suggesting that all patients should have routine thyroid testing.

    • Tee

      I was hoping that someone would point this out. This article was written by a practitioner of “functional medicine” – a field that integrates quackery and pseudoscience with medicine, and preys on patients who don’t know the difference. MR, why are you promoting this? There must be countless doctors who practice evidence-based medicine who would be willing to contribute to your content.

      • Charlsey

        I’ve been dealing with being exhausted all the time and multiple “real” doctors have suggested the exact same things to me, so…

        • Emily B

          Same – I ended up being anemic but all of these were a possibility according to my GP.

        • Tee

          As I said, this modality integrates mumbo jumbo with medicine, which makes it seem plausible. There are many pieces in this article which are medically accurate (eg. anemia, depression) but “adrenal fatigue” is an invented disease with no basis in the medical literature.

      • Grace B

        Big fan of Dr. Yoni Freedhoff up in Canada, he is full of common sense and speaks regularly to press and on talk shows (in Canada mostly). http://www.weightymatters.ca/

    • Shaelah

      Before I went to a naturopath, I saw my doctor and they just said ‘physical stress disorder’ (really, that’s a pretty similar diagnosis as adrenal fatigue but with a more vague name) and told me to keep doing what I was doing (eating well, exercising frequently for health and to manage insomnia) because my blood tests were ‘within normal range.’ I could not keep up with my life and was almost bed ridden, and knew something was not right. Following their advice I continued to get worse. I saw a second doctor, who wouldn’t even listen when I tried to talk and just spoke over the top of me. Saw a third one who listened a bit better but didn’t take the concern seriously.

      So I went to a naturopath / clinical nutritionist. I’m a skeptic, but when you’re desperate you have to do what you have to do. After looking into my family medical history and personal medical history, talking in depth about my symptoms, diet, exercise and lifestyle, she told me I had severe adrenal fatigue, and that while technically ‘within range’ a lot of my blood test results were on the low end of the scale. She told me to immediately cease exercise and focus on rest, and put me on some supplements. She also tweaked my diet slightly.

      Being the skeptic and nerd that I am, I promptly conducted my own literature review of all available scientific publications relating to adrenal fatigue available in my university library. (Yes, that took a while.) I have come to the conclusion that neither side of the argument is right – those who claim it exists can’t base that on solid scientific proof but neither can those who claim it doesn’t. It appears that there isn’t yet the solid basis within the literature for either argument.

      Following her direction instead of the GPs, I saw an ENORMOUS improvement in the space of a couple of months, and was able to return to moderate exercise within the first month.

      I come from a family of medical professionals. I enormous have respect for the medical profession. I’m all for the flu shot, conventional cancer treatment and antibiotics (when actually needed)… and I have no time at all for homeopathy. But I’ve had some truly shocking experiences with conventional medicine and really do believe that the system is broken. It’s not as simple as black and white – it’s not all evil doctors and angel complementary practitioners or the other way round. That sort of rhetoric isn’t helpful at all – things are rarely as simple or as clean cut as many like to make out. It’s certainly not a simple case of ‘pseudo-science quacks preying on those who don’t know better.’

      In my experience, the complimentary practitioner considers the issues in my body holistically, in the true sense of the word not the woo-woo sense. All the doctors I have seen ‘treat’ only the one symptom that I initially bring up. I mean, when I get sick with a cold/flu five times in the space of 2 months, she’s concerned about my immunity, but the doctor just says here are some antibiotics.

      Please tell me, if you were in my shoes, whose advice (based on my own research and personal experience) seems more valid to my circumstance? When the advice given to you by the doctor/s makes you 100% worse and the help given to you by a complimentary practitioner means you dramatically improve? When those members of your family who are in the medical profession acknowledge the issues I’m bringing up? When your naturopath is very pragmatic and insists you continue to see your GP but multiple GPs don’t take your concerns seriously (even though I have never once mentioned the word adrenal fatigue to any GP because I know they will laugh me out of the building)? Can you really question why people are turning away from doctors in droves? I am not saying they SHOULD be ignoring their doctor but isn’t it pretty obvious why I’m personally frustrated with doctors?

      I think I’ve finally found an MD/GP who is sympathetic to complementary practices and agrees that my body is not behaving normally but boy has it taken way longer than it should have!

  • Ma

    It can also be endometriosis – which unfortunately isn’t as easy to treat as “turn the tv off before you go to sleep” – if you have painful periods it’s worth checking as it’s estimated up to 20% of women might have it. There are things you/your doctor can do to ease off some of the symptoms, and maybe make the constant exhaustion and pain somewhat better. A combo of moderate exercise and plentiful rest seems to be helpful to most women with the condition – as it is for most people.

  • joan

    This is just an ad for Parsley Health…I expect better out of MR

  • Teresa

    You only need 15 minutes of sunlight to get your daily dose of Vitamin D. If you walk to/from the office or to go pick up your lunch, that should be enough. The kicker is that sunscreen blocks Vitamin D absorption. I’m the only one in my family who is not Vitamin D deficient and I think it’s because I don’t wear makeup or moisturizer with sunscreen on a daily basis. I’m only really outside during the commute and I doubt that it’s enough time to significantly damage my skin.

  • Natalie Redman

    Great post! I think I might have an iron deficiency so will be going to the doctor to find out if it’s that!


  • very well said! This may explain a few things 🙂 haha

  • 🚗Carlos

    Whoa. I thought it was the only one nagging. Became 50 and dealing with sciatica summer ruined no biking no soccer no beach .i feel down and sleepy could it be my line of work sitting on a desk and working late hours. Any suggestions?

  • Avin B.

    Yes, i agree that my current job is killing me slowly inside. I drag myself to work for long hours 8-10 hours a week and when i get home i stay on my phone watching YouTube or browsing the net until i fall alseep. I hate my job but it pays pretty well ;-;