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Why Do I Get Sleepy from Drinking Coffee?

We really do love coffee. Just look at the number and variety of coffee shops, specialty coffees, and home coffee makers. The National Coffee Association reports 7 out of 10 Americans drink coffee every week and 3 out of 5 drink it every day!

Why do we drink coffee? There are many reasons - from enjoying the taste to being part of the crowd (Think Central Perk in Friends). 

Caffeine’s Stimulant Effect

One very common reason for  coffee drinking is for its stimulant effect. The caffeine in coffee helps people compensate for sleepiness and improve school or work performance. To further increase the stimulant effect, people may select coffee drinks with much higher levels of caffeine, compared to a regular cup of brewed coffee (The amount of caffeine in a cup of brewed coffee is about 100 mg). Soft drinks/soda, energy drinks, tea, chocolate, energy bars, and medicines also contain varying amounts of caffeine. 

Caffeine Content*

Be aware that caffeine may be present in drinks, foods, and medicines and that the amount of caffeine varies greatly. Some examples, compared to 100 mg/cup of brewed coffee,  include:

Coffee, Tea, Soft Drinks/Soda, Other

  • Coffee shop - 80-410 mg

  • Bottles and cans - 75-300 mg

  • Ground - 55-300 mg

  • Tea (bottles, tea bags) - 5-150 mg

  • Soft drinks/soda - 19-69 mg

  • Energy drinks - 75-300

  • Caffeinated waters or drinks - 30-100 mg


  • Chocolate, ice cream, yogurt - 1-66 mg

  • Caffeinated snacks, gels, gum - 6-100 mg


  • Weight loss, caffeine pills - 200-270 mg

  • Pain medicines with caffeine - 65-130 mg

*Note: Some coffees, teas, soft drinks/sodas are decaffeinated and contain very little or no caffeine. 

Caffeine’s Stimulant Effect And Adenosine

Most of the stimulant effects of caffeine are from its action on the chemical messenger adenosine. Adenosine is released from nerve cells and binds to specific receptors throughout the body. When this occurs it has a sleep-promoting effect.

Caffeine is actually an adenosine receptor antagonist, in other words, it blocks adenosine receptors, thus interfering with sleep.

Sugar In Your Coffee

It’s worth mentioning that sugar, often part of coffee drinking, can add to the drowsy feeling.

The sugar content in coffee and other caffeinated drinks also varies greatly. If you drink your coffee black, there’s no sugar, however there are many ways you might add sugar to your coffee. Do you:

  • Add spoonfuls or packets?

  • Use sweetened creamers?

  • Drink coffee shop speciality drinks (with sugar, chocolate, whipped cream, and etc)?

  • Have bottles or cans of sugared, caffeinated drinks? 

Why Does This Happen? Here Are The Reasons.

With all of the information about the stimulant effects of coffee and other caffeinated beverages, foods, and medicines, how can you get sleepy from drinking coffee? It’s odd, but coffee can make you drowsy - just the way you feel before falling asleep.  Why does this happen? There are many reasons.

1. The Sleep Sandwich

Frances O’Callaghan, a professor at Griffith University,  School of Applied Psychology, in Southport Australia uses the term sleep sandwich to describe the lack of night-time caffeine between two days of consuming caffeine

Here’s a possible scenario: Let’s say you drink coffee in the morning, have another cup at lunchtime, and then a soft drink or soda, with one or two refills, at dinner. At bedtime, you cannot fall asleep (The caffeine actually reduces one of the main by-products of melatonin, the sleep hormone). When you do finally fall asleep, you’re unable to stay asleep. How do you feel the next day? Sluggish? Sleepy? Unable to concentrate?  Although the effects aren’t immediate, you are sleepy from drinking coffee.

2. Sleep Quality

Caffeine use affects future sleep quality in several ways. 

You may believe that caffeine earlier in the day won’t impact your sleep, however, a study found that 4 cups of brewed coffee (400 mg of caffeine) right before, 3 hours before, and even 6 hours before bedtime resulted in decreased total sleep time (TST)

Another study showed that coffee affected the normal sleep cycle, with more coffee having a greater impact. Caffeine before bedtime actually shifted the order of the sleep stages.

3. Stress

We know that stress can interfere with sleep. Interestingly, a small study determined that those who are at risk for stress-related sleep problems, also react more strongly to caffeine - i.e. they had increased difficulty falling asleep (sleep latency) compared to those who were not at risk for such sleep problems. This means when you are overly stressed and drink coffee, you are even more likely to have sleep disturbances.

4. Normal Drowsiness

Even 16 hours after the equivalent of 2 cups of morning coffee, caffeine continues to affect the nervous system. It actually slows the increasing drowsiness that is normal after a long day (sleep propensity). 

5. Increased Susceptibility To Other Factors

Caffeine often makes it difficult to sleep - when a person has trouble falling or staying asleep due to caffeine intake, it may be compounded by other interruptive factors like eating close to bedtime, or noise or light in the bedroom. In other words, once you’re awake, you’re more susceptible to these other factors.

6. Caffeine Withdrawal

Daily Coffee Drinkers

Caffeine does not stay in the body for long, depending on a number of factors. For those who are daily coffee drinkers, they’re likely to feel the effects of decreased caffeine, or withdrawal, every night

Regular coffee drinkers have an increased number of adenosine receptors in their nervous systems (When adenosine binds to receptors it promotes sleep).  As a result, they have increased sensitivity to adenosine. If they decrease coffee intake (thereby decreasing caffeine’s blocking of adenosine receptors), adenosine function increases and withdrawal symptoms result.

Symptoms Of Caffeine Withdrawal

A review of dozens of studies of caffeine withdrawal symptoms found drowsiness or sleepiness in 78% of the studies - only headache occurred more often. Other common symptoms are:

  • Feeling tired, low energy

  • Trouble concentrating, feeling foggy

  • Decreased alertness

  • Feeling depressed, unhappy, irritable

In the studies, participants had as little as one cup of coffee (100 mg of caffeine) for 3 to 7 days. They had withdrawal symptoms 12 to 24 hours after having coffee (or other caffeine).  

7. High Coffee Use

We know that caffeine use is associated with daytime sleepiness, but how does the amount of coffee or caffeine affect sleepiness? It is likely that the more coffee you drink, the greater your daytime sleepiness. A survey of close to 5,000 people in Britain found 10.6% of respondents with severe daytime sleepiness - i.e daily and lasting a month or more, drank 7 or more cups of tea coffee daily compared to 5.9% in moderate tea/coffee drinkers.

8. Genetics

You may have noticed that the effects of your coffee drinking are different than those of your friends, family, or coworkers. Again, there are many factors, one of which is genetics. Your coffee drinking habits, as well as the effects of the coffee, are impacted by your genes - meaning how your body reacts and adapts to caffeine (see the information about adenosine receptors above).

9. More About Sugar

Sugar can add to the delayed fatigue that often occurs with coffee drinking, if it’s included with your coffee. At first, you may feel energized and alert from the increase in your blood sugar. However, your pancreas will react to the sugar in your gastrointestinal tract by secreting insulin, which helps your body use the sugar for energy. Your blood sugar will return to a normal level - which may make you feel sluggish after the initial sugar-high. This is sometimes called a “sugar crash.”

10. Other Possibilities

Losing a lot of body fluid or dehydration, causes a number of symptoms. One of them is sleepiness. Although caffeine is a mild diuretic - i.e it increases body fluid removal, it is very unlikely that it would lead to dehydration and the associated symptoms. However, coffee does increase urination and trips to the bathroom. When this happens at night, it is yet another factor in poor sleeping and next-day sleepiness.

Mycotoxins are a type of fungus present in many crops, including coffee beans. There has been much discussion about the presence of mycotoxins in coffee. Exposure to mycotoxins may cause minor symptoms like headache, gastrointestinal problems, and fatigue, and some very serious conditions. Rest assured that many analyses have shown that mycotoxins are essentially destroyed by the coffee roasting and other processes.

How Does This Work In The Body?

In the body, caffeine:

  • Blocks adenosine receptors throughout the body

  • Decreases 6-sulfatoxymelatonin, the main by-product of melatonin

  • Peaks quickly, within in the first 30 minutes after ingestion, and then starts to decline

There are other possible explanations including:

Is Getting Sleepy From Coffee An Indicator Of Any Underlying Conditions?

Getting sleepy from drinking caffeine may mean a lot of things, and it is linked to sleep disturbances, but it doesn’t indicate any underlying conditions. 

How To Minimize The Effect of Sleepiness From Coffee

There are some steps you can take to avoid feeling sleepy from drinking coffee or other caffeinated beverages or foods.

  1. Be aware of the amount of caffeine in foods, drinks, and medicines.

  2. Watch out for hidden caffeine in beverages, foods, and medicines.

  3. Limit the amount of caffeine you consume.

  4. Choose no- or low-caffeine drinks or simply drink more water

  5. Stop caffeine at least 6 hours before bedtime

  6. Watch for other sleep-interfering habits and practices that may also interfere with sleep, thus adding to the caffeine-sleep-caffeine cycle.

Want help with sleep? We can help. You can start Goodpath’s Sleep Program by taking our brief assessment.