Pssst—your boss isn’t looking over your shoulder, right? Good, time for some truth: do you ever feel….well, just a little….sleepy during the day? And maybe, possibly, you’ve felt your eyes getting just a bit heavy during that post-lunch meeting on the new standard operating procedures for logistics record-keeping?

If this sounds like you, the truth is that you’re really not alone. According to the most recent survey on the subject, 76 percent of workers feel tired many days of the week, and 15 percent even fall asleep during the day at least once per week. In fact, a lack of sleep among the U.S. workforce costs approximately $411 billion in lost productivity.

Why are so many feeling so tired during the day? Well, the answer is not all that surprising: we’re not getting the sleep we need. Before we look at why this might be and how to beat it, let’s look at what’s going in our bodies when we can’t shake our sleepiness.

Our sleep debt

One of the main biological big honchos when it comes to getting you to sleep is a chemical in your brain called adenosine. From the moment you wake, adenosine builds up in your brain creating sleep pressure, and (as you can guess) this pressure comes to its peak in the evening, making you tired.

When you don’t get enough sleep, adenosine concentrations remain very high in your body, as they haven’t been depleted by good sleep. Because of this, you have to slog through daytime sleepiness the next day, relying on the temporary fix of caffeine just to make it through the morning. Sleep scientist Matthew Walker in his book Why We Sleep calls this our “sleep debt”—and unfortunately it can never be fully “repaid”.

Walker tells us that this sleep debt going unpaid continues to accrue every night that you get inadequate sleep. Carrying this debt for a long period of time then turns into chronic sleep deprivation, which nobody wants, but sadly so many just get used to as the new normal.Why you may be tired during the day

The sleep debt causing you to feel tired during the day could be building up in you for two reasons:

First, the most obvious: you’re not giving yourself enough time to sleep. Solution? That powerful cocktail of best sleep practices that we call sleep hygiene. Go down the list and see if there’s something missing:

  • Stick to a consistent sleep schedule.
  • Exercise is great for sleep, but don’t do it too late in the day, as this can prevent you from falling asleep.
  • Avoid caffeine and nicotine.
  • Avoid alcoholic drinks close to bedtime.
  • Avoid large beverages and meals late at night.
  • Don’t take naps after 3 p.m.
  • Relax before bed.
  • Take a hot bath before bed.
  • Keep your bedroom cool, completely dark, and free of any screens such as phones, TVs, tablets, etc.
  • Get the right sunlight exposure, as this will help regulate your sleeping pattern.
  • Don’t lie in bed awake. If sleep doesn’t come on after lying in bed for more than 30 minutes, or you start to feel anxious or stressed, get up and do a relaxing activity in a different room, and head back to bed once you feel tired.

Second, you know that you’re giving yourself at least an eight or nine hour sleep opportunity, but you’re still feeling daytime tiredness. This may be a sign of something deeper going on, such as a potential sleeping disorder, which may be interrupting your sleep or keeping it from operating at its peak ability. You should consult your doctor as soon as possible and discuss possible solutions.

The best day possible

Though wanting to nod off during the day may not seem very serious, it is most likely a sign of deeper sleep deprivation, which everyone should begin to take more seriously. While it’s true that daytime sleepiness wreaks havoc on workplace productivity, the real takeaway here is that when you’re not sleeping well, you’re just simply not living your life to the fullest. Remember: making the most of tomorrow means getting great sleep tonight!