It’s almost like clockwork. One minute you’re powering through your to-do list, and the next you’re struggling to keep your eyes open, rereading the same email three times, or wondering if it’s too late for another cup of coffee. If your energy seems to disappear every afternoon, you’re not imagining it. We’ve all been there, but the reason may not be as obvious as you think.

While it’s easy to blame a poor night’s sleep or assume you just need more caffeine, there are several surprising factors that can leave you feeling drained by mid-afternoon. The good news is that once you know what’s behind your daily slump, a few simple tweaks to your routine can make a big difference. We asked experts to break down the most common culprits behind an afternoon energy crash—and how to stop it before it hits.

• ABOUT OUR EXPERTS: Talia Follador, R.D.N., L.D.N., is a registered dietitian nutritionist and founder of Follador Nutrition Services LLC. Katharine Rosenthal, R.D.N., is a registered dietitian nutritionist and founder of Be Well Table. Stacey Woodson, M.S., R.D., L.D.N., is a registered dietitian nutritionist and founder of The Earth-Centered Dietitian. 

5 Reasons For Your Afternoon Energy Crash 

1. You’re Dehydrated

You might not feel thirsty, but even mild dehydration can quietly chip away at your energy, alertness, and concentration. “When you are even slightly dehydrated, your blood volume drops, making it harder for your body to efficiently deliver oxygen and nutrients to the brain,” says Stacey Woodson, M.S., R.D., L.D.N., founder of The Earth-Centered Dietitian. The result, she explains, is sluggishness, difficulty concentrating, and a fogginess that feels like low energy.

Read More: 7 Signs You’re Dehydrated

While dehydration can happen at any time, it often creeps up in the afternoon. This is because many people drink plenty of fluids in the morning but then taper off as the day gets busier, leaving them dehydrated (and tired!) by mid- to late afternoon, says Katharine Rosenthal, R.D.N., founder of Be Well Table. 

To stay ahead of dehydration, Woodson recommends sipping water consistently throughout the day instead of waiting until you feel thirsty. As a general goal, women should aim for about 11.5 cups of fluids a day and men about 15.5 cups, though needs may be higher if you’re active or spending time in the heat. Most of those fluids should come from water, but you can boost your intake with water-rich foods like cucumbers, citrus, and berries, she adds. The occasional electrolyte supplement in your drink can be a smart choice for hydration, too.

2. You’re Over-Caffeinated

Caffeine can feel like it’s giving you energy, but it’s possible it’s just delaying fatigue. “Caffeine works by blocking adenosine, a chemical that builds up in your brain throughout the day and signals that your body needs rest, but adenosine doesn’t stop accumulating just because it’s being blocked,” Rosenthal says. When the caffeine wears off—typically four to six hours after consumption—that built-up adenosine hits all at once, she explains. So, if your last cup of coffee or tea was at 9 a.m., you could experience an adenosine rebound between 1 and 3 p.m.

Drinking large amounts of caffeine early in the day, and especially continuing throughout the afternoon, can also create a cycle of poor sleep and next-day fatigue, says Talia Follador, R.D.N., L.D.N., founder of Follador Nutrition Services, LLC. To help break that cycle, she recommends limiting caffeine to 300 milligrams (mg) or less per day and avoiding caffeine within roughly eight hours of bedtime. (For reference, an average cup of coffee contains about 90-95 mg.) 

3. You Ate a High-Refined Carb Lunch 

What you eat at lunch can have a big impact on how you feel a few hours later. A meal that’s heavy in refined carbohydrates (like white bread, pasta, pastries, and sugary drinks) but low in protein, fiber, and healthy fat is digested quickly, leading to a rapid spike in blood sugar followed by a sharp crash, Woodson says. “That dip then triggers a hormonal response that leaves the brain temporarily under-fueled, which is why you may feel foggy, sleepy, or hungry again soon after eating.”

Read More: 7 Ways To Make Your Carb Consumption More Blood Sugar-Friendly

The good news is that a few simple changes to your lunch can help keep your energy on a more even keel. Follador recommends building balanced meals with protein, fiber-rich carbohydrates, and healthy fats. These nutrients help slow digestion, keep you fuller for longer, and minimize large swings in blood sugar. This might look like grilled chicken over quinoa with roasted vegetables and avocado, or a turkey and hummus wrap on a whole-wheat tortilla paired with carrots and an apple.

4. You’re Running On Sleep Debt 

If you’ve been consistently getting less sleep than your body needs—even by just an hour or two each night—it can catch up with you in the afternoons. Your drive for sleep builds throughout the day, making you feel more fatigued by the p.m. hours, Woodson says. “When you are not getting enough quality sleep, the afternoon dip lands on top of an already tired brain, and sleep deprivation reduces focus, reaction time, and working memory, making the natural circadian slump feel significantly more intense.”

The most effective way to pay off sleep debt? Prioritize getting enough quality sleep on a nightly basis. That means aiming for 7-9 hours of sleep each night, sticking to a regular bedtime and wake-up time, and creating a bedtime routine that helps you wind down, Woodson says. While one good night of rest can help, consistently meeting your sleep needs makes the biggest difference in your daytime energy.

5. Your Body Is Following Its Natural Circadian Rhythm 

If you feel particularly sleepy in the early afternoon, your body’s internal clock may be to blame. According to Rosenthal, everyone experiences two natural low-energy periods each day: one in the middle of the night and another in the early to mid-afternoon. “This is biology,” she says. “During the afternoon dip, body temperature drops slightly, melatonin nudges up, and alertness signals from the brain quiet down.” 

You can’t eliminate this natural dip, but you can make it feel less noticeable. Follador explains that poor sleep, stress, dehydration, and other lifestyle habits can turn a normal lull into a full-on energy crash. Getting enough sleep, staying hydrated, eating balanced meals, and taking a short mid-day walk or stepping outside for a few minutes can all help you feel more alert until your energy naturally rebounds.

The Bottom Line

Some degree of afternoon sleepiness is a normal part of human biology, so rather than trying to eliminate it completely, focus on habits that make the dip feel less steep. Getting enough sleep, staying hydrated, eating balanced meals, and keeping your caffeine intake in check can all help keep your energy steadier.

That said, if your fatigue is severe, happens daily despite healthy habits, or is accompanied by symptoms like unintentional weight loss, shortness of breath, dizziness, or needing to nap for hours every afternoon, Follador says it’s worth talking to your healthcare provider. The occasional afternoon slump is normal, but persistent fatigue can sometimes point to an underlying medical issue.