why am i tired all the time
Ryan Johnson

You got a good night’s sleep, you’re not sick, you ate breakfast and even did 30 minutes of cardio—so why do you feel like you’re dragging yourself through the day in a jet-lagged haze?

If you really did get enough sleep—many Americans struggle to do so, with one in three considered sleep-deprived, or getting less than seven hours a night—then constantly feeling tired can be a sign of a serious health condition, such as chronic fatigue syndrome, Lyme disease, thyroid issues, or depression. It’s also the most common symptom of menopause. If you think you might fall into one of these categories, see your doctor (or a therapist, in the case of depression), who can help diagnose you and guide you to a treatment that’s right for you.

But if you’re just feeling physically and mentally (and even emotionally) sluggish, and you’ve ruled out stress or boredom (aka the endless Zoom meeting), consider one of these surprising culprits. They’re simple to remedy, and addressing them will benefit your overall health, not just your energy level.

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1. Being even just a little dehydrated

Our bodies are made up of around 60 percent water, which is key to keeping our blood flow, brain and muscle function, metabolism, and the transportation of nutrients operating at their very best. Given how much H2O that is, you’d think we’d be totally fine if a little bit simply evaporated away. But studies have found that even a slight decrease—meaning less than 2 percent water loss—can impact our daily functioning and make us feel not just fatigued and less focused but also potentially more prone to anger, anxiety, and depression.

One possible explanation involves the production of the antidiuretic hormone arginine vasopressin (AVP). When you become dehydrated, your blood loses water and starts to thicken, triggering your hypothalamus, the deep part of your brain that links your endocrine and nervous systems, to produce more AVP, says Evan Johnson, PhD, an associate professor of kinesiology and health at the University of Wyoming. “When AVP levels go up, that signals to your kidneys that it’s time to reabsorb water from within your body and not expel it as urine.” But here’s the catch: Studies suggest that chronically higher levels of AVP may also lead to mood changes, including fatigue and depression.

The fix: Make sure you’re drinking enough fluids, whether water, seltzer, coffee, or tea (they all count). While the old-school recommendation to drink eight glasses a day is essentially a myth, you can use it as a lodestar, says Johnson, though don’t stress about counting ounces. Rather, keep tabs on your urine color—it’s the only way outside of a lab to gauge whether you’re mildly dehydrated, says Johnson. (Once you feel thirsty, you’ve passed the mild mark, he cautions.) “You’ll know if you’re well-hydrated if it’s consistently in a light-yellow range and you take about six to eight pee breaks a day.”

2. Eating too much sugar and/or processed food

    If you’ve been feeling dips in energy during the day, it might be time to audit the sugar in your diet—including “hidden” sugars in savory foods. “Added sugar isn’t just in sweets, sodas, or energy drinks. You can find significant amounts in things like ketchup, pasta sauces, and salad dressings,” says nutritional psychiatrist Uma Naidoo, MD, director of Nutritional & Lifestyle Psychiatry at Massachusetts General Hospital and author of This Is Your Brain on Food.

    Added sugar also lurks in the foods that start our day, from yogurts to the refined carbs we know and love, like bagels, muffins, and scones. You might feel that they give you a boost of energy, but studies suggest you’re setting yourself up for a crash and burn soon after. Why? When sugar and refined carbs are metabolized, they cause a spike in insulin, which can then lead to a precipitous drop in blood sugar. For many people, that drop manifests in feelings of tiredness (acute sleepiness) and fatigue (an overall depletion in energy). In fact, a 2019 review of 31 different studies found that most subjects felt “higher levels of fatigue and less alertness” within 30 to 60 minutes after consuming foods high in refined carbs and sugar.

    That drop may also induce feelings of depression in some individuals. A small study published in the journal Appetite looked at 82 adults without diabetes and found that those who ate a meal that had a high glycemic load, or one high in sugars and refined carbs, also reported a significant decrease in energy and an uptick in feelings of depression afterward. So that afternoon cookie you think will perk you up may actually bring you down.

    So that afternoon cookie you think will perk you up may actually bring you down.

    Sugar may also induce these feelings because, just like lack of sleep, it triggers inflammation in the body, says Naidoo. “Most added sugars, such as high-fructose corn syrup—and this does not include sugar in fruit, which comes with the added benefits of fiber, minerals, and vitamins—are pro-inflammatory substances, and the resulting changes in the gut and the brain may ultimately lead to feelings of depression and fatigue.”

    The fix: Starting last year, the U.S. Food and Drug Administration began requiring that companies list “added sugars” on nutrition labels. Woot! So grab your readers and follow the recommendation of the Dietary Guidelines for Americans and keep added sugars to less than 10 percent of your daily caloric intake (that's a max of 50 grams for a 2,000-calorie diet). Better yet, skip packaged foods as much as you can and focus instead on nutrient-dense whole foods, like whole grains and fresh fruit and vegetables. So, for example, if granola (which is often high in sugar) and yogurt are your morning jam, make the latter plain (no added sugar) and try adding just steel-cut oats with some blueberries and a little honey and cinnamon to sweeten it instead, suggests Naidoo. And make sure not to use artificial sweeteners as a substitute: “These can cause a similar sugar crash as regular sugar because the taste receptors in the tongue and in the gut still get activated; they think sugar is coming their way,” says Naidoo.

    3. Low vitamin or mineral levels

      Many people in the United States don’t meet the recommended daily adequate intake of vitamins and minerals and, as a result of these inadequacies, end up experiencing “covert symptoms only that are difficult to detect clinically,” according to a Linus Pauling Institute report. What are some of those “covert symptoms”? You guessed it: fatigue and mood changes.

      Some key vitamins and minerals to watch out for, says Naidoo, are:

      • Vitamin D, the lack of which has been linked to depression and anxiety.
      • Vitamins B1 (thiamine), B6, B9 (folate), and B12, all of which, when low or deficient, can make you feel tired, sluggish, or even depressed. B12 is found only in meat, fish, poultry, eggs, and dairy products, so vegans and vegetarians (even those who eat eggs and dairy, studies have found) and people with Crohn’s or celiac disease (who have trouble absorbing the vitamin) often don’t get enough.
      • Iron, which is of particular concern for women who are still menstruating (blood loss lowers iron levels). A deficiency is linked to depression.
      • Magnesium acts as an anti-inflammatory, which may be how it helps protect against both conditions.
      • Vitamin C is a crucial antioxidant, especially in the brain; fatigue is a common symptom when levels are low.

      The fix: Eat the rainbow: red, orange, yellow, green, and blue fruits and vegetables, plus nuts, legumes, and lean proteins. If you can’t eat certain foods, don’t worry. “Most of us have gaps in our eating, so after paying attention to those and seeing what you might be able to fill back in with food, you may need to turn to supplements, like a vitamin B complex,” says Naidoo. (For a daily vitamin D boost, she also recommends spending 10 minutes in the sun without SPF so it can penetrate the skin.) But always talk to your doctor before stocking up on supplements. They can test your levels to help you target exactly what you need, and in what dosage.