Why Am I So Tired?

Medically Reviewed by Brunilda Nazario, MD on November 15, 2023
3 min read

It's the middle of the day and you just can't seem to get out of first gear. And it's not the first time. 

What’s making you feel so wiped out? There is a long list of possible reasons, and many of them are things that you can influence. Check out these common culprits for fatigue and get some pep back in your step.

Everyday habits can make a big difference.

"With my patients, I talk about the three pillars of health: sleep, diet, and exercise," says Theodore Friedman, MD, PhD, chair of medicine at the Charles R. Drew University of Medicine and Science in Los Angeles. "If you aren't getting good sleep, it's hard to eat well, and it's hard to exercise. And the same is true the other way around. They're all related."

So try not to short-change yourself on shut-eye. Adults need 7 to 9 hours of sleep. Eat a balanced diet of fruits, veggies, and lean protein, and get a regular dose of physical activity.

If you've checked all those boxes and you still drag through your days, it might be time to check possible medical causes of fatigue.

It's a disorder that makes it hard for your blood to move oxygen around your body. A common type is called "iron-deficiency" anemia.

Iron acts like a train car that transports oxygen in your blood. "People with low iron don't have enough cars on their train," Friedman says. "They're tired, they get dizzy when they stand up, they get brain fog, they get heart palpitations."

Your doctor can check you for anemia with a simple blood test.

Doctors don't know exactly why it makes people so tired. One likely reason is that your body uses lots of energy to deal with your frequent changes in blood sugar levels.

What doctors do know is that fatigue is one of the most common symptoms of diabetes. It has other signs, too. You may feel thirsty and need to go to the bathroom often.

It's a small, butterfly-shaped gland that sits in your neck. It makes a hormone that helps control how you use energy. When your thyroid gland is out of whack, you're out of whack.

"People with an underactive thyroid are going to feel tired," Friedman says. "Their cells aren't working well, they're sluggish, and their reflexes are slow."

Your doctor may test your blood for thyroid hormone to see if it's to blame for your fatigue.

Extreme tiredness is a common symptom of congestive heart failure, which happens when it doesn't pump as well as it should. If you have it, your fatigue usually gets worse when you exercise. You might also have swelling in your arms or legs and shortness of breath.

This disorder keeps you from getting enough oxygen when you sleep, which means you won't get real rest during the night.

"The brain notices you're not getting rid of your CO2, and it wakes up really briefly in an alarmed state," says Lisa Shives, MD, director of the Sleep Medicine Center at the University of California, San Diego School of Medicine. You don't even realize it, which makes it hard to figure out why you're so sleepy during the day.

"You don't get into REM -- the sleep that makes you feel best," Shives says.

A device called a continuous positive airway pressure (CPAP) machine can help keep your airways open for a solid night's sleep.

If you're a woman who's going through menopause, you may find it hard to get good sleep. Your hormones change a lot at this time, which give you night sweats and hot flashes. That can keep you up at night and leave you dragging during the day.

It robs your brain of the chemicals it needs to work at its best. One of those is serotonin, which helps regulate your internal body clock.

Depression can lower your energy levels and make you feel tired during the day. You may also find it hard to fall asleep at night, or you might wake up earlier than you want in the morning.

Talk to you doctor if you think you're depressed. Talk therapy and medicine can help.