9 signs you're not sleeping well - and how it's affecting your work success

2. You're missing work due to illness.

"Lack of sleep has been shown to weaken our immune system and increase the likelihood of coming down with a cold," he explains. Poor sleepers generally miss three more days of work each year than good sleepers.

"Our data suggests that employees are missing three hours of work per week on average (in late starts, early finishes, and missed days) due to poor sleep."

Poor sleep has also been shown to lead to an increased likelihood of type II diabetes, cardiovascular disease, obesity (by 50%), and alcohol dependence, Hames says.

3. You find the little things get to you.

A lack of sleep can affect your mood and resilience, leading to greater irritability and a higher likelihood of becoming overwhelmed by small issues, says Hames. At work, this can have a serious impact on your relationships with colleagues, managers, and clients.

4. You spend a lot of time on Facebook and online shopping at work.

Poor sleep has been shown to reduce self-control and increase the likelihood of "cyberloafing," which is surfing Internet sites unrelated to work, he says. When you spend more time on sites like Facebook or Amazon, you're spending less time working.

5. You find it difficult to think clearly.

"Sleep deprivation has a noticeable impact on cognitive functioning, limiting innovative thinking, reducing working memory span by 38%, and increasing the incidence of false memories," Hames says. This can be detrimental to your performance at work.

6. You make impulsive decisions.

Have you been reaching for a brownie at lunch, when you're normally very health-conscious?

"Restricted sleep increases food intake and impairs our ability to resist food cravings," he explains.

And unfortunately, high-fat, high-sugar meals and snacks make us have low energy and tend to decrease our productivity, Lisa De Fazio, a healthy-lifestyle expert and registered dietitian, previously told Business Insider.

7. You feel very stressed.

It is easy to see how stress negatively interferes with your ability to get or to stay asleep. Not being able to put your mind to rest at the end of a busy day is one of the most common causes of poor sleep.

However, sleep and stress also interact in the other direction: during the day, following a poor night of sleep, you are significantly more likely to perceive experiences as being stressful — and this can slow you down or distract at work.

8. You have less energy.

If you're feeling the need to take naps, that's probably a sign that you're not getting enough sleep at night. If your sleep seeps into the daytime, it is likely that being awake will seep into your night, and this will only make your sleep worse.

Low energy equals low productivity. It's as simple as that.

9. You feel depressed or anxious.

"Research has shown that sleep-restricted healthy subjects — as well as patients free from psychiatric illness but with chronic sleep disturbance — show impairments in emotional well-being such as depression and anxiety," he says. When you feel anxious or depressed, you're less likely to be motivated at work — and you may call in "sick" or take personal days more often.

What to do if lack of sleep is affecting your work success:

Hames says if you're not sleeping well, you should think about making your day "pro-sleep" when you're awake. What does this mean? "Try to get as much natural light as possible: It will not only help you feel more awake during the day, but it will signal to your body when it's time to wind down at night."

And if you're having problems falling or staying asleep during the night, avoid napping during the day, he adds.

Another trick is to prepare well for bed.

"Start relaxing and preparing for sleep at least 60 to 90 minutes before bed," he suggests. "Stop any work or intense activity, don't have any intense conversations, and spend some time doing other things before getting into the immediate pre-bed activities like brushing your teeth, putting your pajamas on, or setting your alarm clock. Go to bed only when you feel sleepy, not just tired out."

Finally, he says, keep in mind the number of hours of sleep you need varies from person to person. "There's not a right or wrong amount."

Don't assume you need the often-recommended 7-8 hours. "Although this is the average, everyone's different," Hames says. "In fact a shorter, more compacted sleep may mean a better quality sleep."