Are you tired all the time? Join the club: according to the CDC, over one-third of adults report sleeping less than seven hours a night, which is the minimum amount recommended for optimal health.

So if you’re tired all the time, start there: Are you getting enough sleep?

If the answer is, “I think so,” and you’re still chronically exhausted, take this quiz to explore some of the possible reasons. Most importantly, talk to your doctor; fatigue can be caused by a nearly countless number of health issues, both physical and mental.

12 POSSIBLE REASONS THAT YOU’RE TIRED ALL THE TIME

1. Do you exercise too much or too little?

Exercise boosts your energy and mood and improves your sleep, all of which help you feel less tired. If you’re not getting any exercise, you’re missing out on these benefits and may be feeling extra sleepy. Of course, there’s such a thing as going overboard: too much exercise can lead to exhaustion.

2. Do you drink alcohol at night?

As anyone who has gotten drowsy after a glass of wine can attest, alcohol can help you fall asleep. But what many people don’t know is that alcohol disrupts the quality of your sleep in a number of ways, including by blocking REM sleep, the most restful kind. So even if you feel like you slept all night and you don't have obvious hangover symptoms, you might be dragging during the day.

3. Are you drinking enough water?

Even mild dehydration can slow your mental gears and make you tired. To stay hydrated during the day, drink plenty of water, snack on raw fruit and vegetables or yogurt.

4. Are you overdoing it on caffeine?

You drink coffee to rev up your energy, not drag you down. But, too much coffee can have the opposite effect. If you’re consuming more than 4 cups of coffee each day, you can run into trouble. Some over-caffeinated symptoms include insomnia, irritability, headaches, anxiety, and fatigue. Switch to tea, which contains less caffeine yet can still give you a boost in the morning or afternoon.

5. Do you have a vitamin D deficiency?

Many people don’t get enough vitamin D from natural sunlight or the foods they eat. Vitamin D is critical for healthy bones. Low levels are linked to osteoporosis and may even raise cancer and diabetes risk. One of the symptoms of low vitamin D in the body is fatigue.

6. Do you wake up abruptly in the middle of the night gasping for air or do you snore loudly?

Sleep apnea, in which breathing repeatedly stops during sleep, leads to daytime tiredness even if you don’t realize you’re waking up. It also significantly raises your risk of cardiovascular and other health problems, so if you think you might have it, talk to a doctor.

7. Have you reviewed your medications?

Many common over-the-counter and prescription drugs can make you tired, including allergy drugs, antidepressants, blood pressure medications, and opioids. Your doctor should be able to tinker with your dosage or change the medication to help.

8. Are you dealing with mental illness?

Most people know that one of the symptoms of depression is fatigue, but it’s also a common symptom of anxiety disorder and chronic stress. Grief can also cause fatigue.

9. Do you also feel weak, short of breath or dizzy?

These symptoms, along with fatigue, can indicate anemia, when your blood doesn’t carry enough oxygen to the rest of your body. This is a very common cause of fatigue and very easy to check with a simple blood test. It’s particularly a problem for women, especially those who are having heavy menstrual periods. To enhance your iron levels, eat an iron-rich diet, heavy in meats and dark, leafy greens.

10. Have you had your thyroid tested?

Hyperthyroidism, when your body makes more thyroid hormone than you need, can cause fatigue and muscle weakness. Likewise, hypothyroidism, when your thyroid gland isn’t active enough, can cause fatigue and joint and muscle pain.

11. Are you always thirsty and peeing a lot?

These symptoms, along with fatigue, blurry vision and feeling very hungry, can be early signs of diabetes.

12. Are you viewing blue light at night?

Exposure to blue light at night sends messages to your brain that interrupt processes that prepare your body for a restful night of sleep. The biggest culprits are devices that are commonly used within the hours before going to sleep: computer screens, smartphones, lights, TVs, and even the light inside your fridge all produce blue light. If you're using these devices at night, then you aren't getting the highest quality of sleep possible.

13. Have you talked to your doctor about your heart health?

Fatigue can be a symptom of cardiomyopathy, an umbrella term for diseases of the heart muscle, pericarditis (an inflammation of the sac around your heart), or heart failure. People who have two or more of the following symptoms should be evaluated for heart failure: fatigue or feeling lightheaded, shortness of breath, chronic coughing or wheezing, buildup of fluid, nausea or lack of appetite, confusion or impaired thinking and high heart rate.

These are just a few habits and conditions that can cause excessive tiredness. Talk to your doctor to figure out together what might be causing your sluggishness so you can fix it.