Many factors can cause you to feel tired, such as stress level, dehydration, your diet, and even not being active enough. Here are some common reasons for feeling tuckered out.

You’re Under Stress

Stress can eat you alive, leaving you feeling emotionally spent. That’s because the stress response readies your body to fight a threat or flee from it, causing the body to burn through its energy stores much more quickly than usual.

What’s more, stress contributes to depression and anxiety, which can also cause fatigue, and may interrupt your sleep patterns as well.

And because today’s stress sources tend to be pervasive and ongoing, this physical response never shuts off, taxing the body even more; if it becomes chronic, stress can eventually contribute to physical disorders such as high blood pressure.

One place to start when trying to reduce your stress levels is your to-do list, including work, family and social obligations: Are all the tasks on your list really necessary, or can someone else help you handle them? Have you scheduled enough time for self-care?

Getting more exercise also helps, as do relaxation tools such as the consistent practice of meditation, tai chi or yoga. In addition, spending time with loved ones (including pets) can also help diffuse stress.

You’re Dehydrated

Your body is about 60% water, so staying hydrated is important to fend off not only fatigue but also such problems as headaches, light-headedness, irritability and constantly feeling cold. (Dehydration can even cause sugar cravings.) That’s because not drinking enough water can affect how your organs operate while also impeding blood circulation.

Most people need to drink between six and eight glasses of water a day to function at their peak; your needs will vary with the weather (the hotter it is, the more water you lose) and exercise levels. If plain water tastes blah, try adding lemon slices.

You’re Not Sleeping Well

Just can’t seem to get enough sleep? No sleep at night means no energy during the day.

To get more sleep, start by shutting off smartphones and other screens (including the TV) at least an hour before bedtime; the blue light these devices emit affects your body’s production of melatonin, the hormone that regulates the sleep/wake cycle. (Melatonin is available in supplement form.)

Make sure your bedroom is fairly cool by setting the thermostat between 60 and 68 degrees, and dark; if there’s a lot of light in your neighborhood, consider investing in a set of light-blocking curtains or drapes. Go to bed and get up on a fairly consistent schedule and try to avoid sleeping in on weekends.

Also, watch your timing in terms of what you eat and drink—don’t eat large meals later in the evening. Cut off the caffeine four to six hours before bedtime; make that two to three hours for alcohol.

One other thing: If you’ve been told that you snore, visit a sleep specialist. Snoring and fatigue are signs of sleep apnea, in which breathing repeatedly stops and starts throughout the night.

You’re Not Eating Right

Poor diet can result in an extensive list of health consequences, constant tiredness among them.

Eating too much junk food—with its high levels of added sugars, unhealthy types of fat and chemical additives—can not only provoke fatigue on its own but also result in the kinds of nutritional deficits that can lower energy levels even more.

It’s often easier said than done, but basing your diet on fresh produce, whole grains, healthy fat sources and clean protein can really make a difference in how you feel.

You’re Sick

It makes sense that you’re not going to be full of energy if you just don’t feel well. That makes fatigue a key symptom in a long list of disorders.

Upper respiratory infections are an obvious (and generally self-limiting) cause of tiredness, but fatigue plays a role in more significant health concerns as well. And while many of these conditions tend to become more common with age, a number of them—from chronic fatigue syndrome to mononucleosis (usually caused by infection with the Epstein-Barr virus) to undiagnosed diabetes—often strike younger people.

If you have fatigue that lasts even after you’ve made some lifestyle adjustments, it’s time for a trip to your practitioner for a thorough workup.

You’re Low on Iron

This is probably not the first thing you’d consider as a reason why you’re tired all the time. But it’s more widespread than you think. In fact, iron deficiency is the most common nutritional deficit worldwide.

Women in their childbearing years, athletes, and vegetarians and vegans are just some of the groups prone to low iron.

Clean sources of animal protein, such as grass-fed beef and wild-caught fish, can help you build your iron stores. Iron is also available in supplemental form, but you have to be careful—some types can provoke digestive distress. For greater comfort and absorption, look for a product that provides organically bound, high-potency iron along with key cofactors such as vitamin C.

You’re Too Sedentary

If you’re tired you should rest more, right? Actually, no: Too much couch time actively contributes to fatigue.

Because of the way it messes around with your hormones, being inactive disrupts not only your sleep patterns but also your appetite levels—food cravings tend to be harder to control. It also promotes the development of body fat instead of lean muscle mass; the more fat you carry and the weaker your muscles are, the more tiring it is just to climb a flight of stairs or walk to your car.

What’s more, researchers have found a link between inactivity and feelings of emotional exhaustion.

The good news: Exercise can help counteract all these effects. Being active boosts energy levels and promotes a sense of greater well-being through the release of endorphins, responsible for what’s known as “runner’s high.” It also sharpens thinking skills and concentration.

The trick is finding enough motivation to get yourself off the couch. Promise yourself a nonfood reward, such as a spa day for a week’s worth of effort. The idea is to give your brain a reason to buy into hitting the gym or lacing up your sneakers.

One of the best motivators is sharing your fitness plans with other people who can help hold you accountable; for example, you can sign a contract that says you’ll pay a friend $10 for every exercise class you skip. An even better idea is to recruit that person as an exercise buddy—the two of you can help keep each other on track.