According to the National Coffee Association, the amount of coffee drank in the U.S. has increased by 5% since their previous survey in 2015. The results found that 62% of American’s drink coffee daily and the average is over 3 cups per day. Even though many people are sipping on that morning cup of Joe for a boost of energy, there are others who wonder, “Why does coffee make me sleepy?”
Though the caffeine found in coffee is a stimulant, you can still feel tired after drinking coffee. There are other effects caffeine can have on your body to make you feel like it is nap time. We’ve broken down the reasons why and how you may be able to minimize these effects.
Why does coffee make you sleepy & tired?
Everyone is different and reacts to coffee in different ways. Effects can vary based on the amount of coffee you drink, what you put in your coffee, and how caffeine impacts your brain.
Coffee blocks adenosine
Adenosine is a chemical in our body that plays an important role with our sleep. When we’re awake our brain produces adenosine levels which gradually rise every hour, and it decreases when we’re asleep. Normally, when adenosine is produced it begins to bind to receptors in the brain which slows brain activity gradually in order to prep for sleep. When you drink caffeine, research has shown that it actually blocks adenosine from connecting to brain receptors.
Caffeine has a half-life of about 4 hours according to the Institute for Scientific Information on Coffee, for example, if you drank 200 mg of caffeine after 4 hours you will have 100 mg still in your system. The effects of caffeine, including energy, tends to peak 15 to 45 minutes after drinking it as your liver works to metabolize it. Once caffeine begins to break down, the side effects go away.
Even though caffeine blocks adenosine from binding to its receptors, the brain doesn’t stop producing it. Therefore, once caffeine is metabolized, all of the adenosine molecules that were produced can bind to receptors and may create a feeling of sleepiness. So, if you are wondering “why caffeine makes me sleepy”, then this could be your reason.
It’s the sugar in coffee
If you don’t drink your coffee black, the additives may be the cause of feeling sleepy. Sweetening your coffee with honey, syrups, whipped cream, or sugar can result in a sugar spike followed by a sugar crash due to it being a simple carb.
When you eat sugar, your body breaks it down into glucose to be used as fuel. Simple carbs are digested quickly and therefore create a spike in blood sugar. In order to offset the spike, your body produces a hormone called insulin which helps glucose exit the blood and enter into cells for energy. Since insulin removes glucose from the blood, your blood sugar levels drop which Sanford Health says can result in symptoms such as:
- Fatigue and anxiety
- Lack of concentration
Beyond impacting energy levels, research also shows high sugar intake can lead to serious medical conditions including diabetes and heart disease. It is advised to stay away from sugar to overcome brain fog and anxiety.
You may be dehydrated
Caffeine is a diuretic which means it makes you urinate more often. The reason behind this is because caffeine increases the blood that goes through your kidneys causing them to release more water. Although there is some belief that this can lead to dehydration, research has found that moderate intake of coffee typically does not create dehydration and may even contribute to hydration.
A small 2017 study published in Frontier Nutrition had 10 healthy adults consume 200 mL (6.8 ounces) of water along with low caffeine (269 mg) and high caffeine (537 mg) to determine if there was any effect on their fluid balance. The result found that the high caffeine coffee did have a short-term diuretic effect, but the low caffeine and water were hydrating.
The problem with that study is participants were also drinking water along with coffee. What happens when you may already be slightly dehydrated? Can coffee replenish fluid levels without the addition of water? A 2020 study published in Nutrition Today had mildly dehydrated healthy subjects drink plain espresso coffee (which equaled about the same amount of caffeine in a cup of regular coffee) to see how it affected fluid replacement. It was determined that the control group who received water alone had improved hydration status whereas the espresso hindered fluid replacement.
A common symptom of dehydration is fatigue, and if you’re unknowingly dehydrated, drinking coffee without water may make it worse and you might become tired after drinking coffee. Dehydration can also include other symptoms like:
- Dark colored urine
- Extreme thirst
If you’ve recently been trying to cut back on coffee, you may be feeling tired from caffeine withdrawal since you’re not drinking as much as you’re used to. A 2018 article published in Experimental Pharmacology and Drug Discovery states that withdrawal of caffeine after 10 days of high intake (1,250 mg/day) can increase:
It isn’t just high amounts of caffeine either. The same study found drowsy and sleepy feelings coming from people used to drinking 579 mg of caffeine per day and as low as 100 mg per day. If this could possibly be the cause of your fatigue, Cleveland Clinic states that withdrawal symptoms could last approximately 2 to 9 days. But if you are determined to lower your caffeine intake and yet stay energetic, you can check out this article on how to stay awake without caffeine.
You’ve built a tolerance to caffeine
You may have once felt a burst of energy from drinking your morning coffee, but now all of a sudden, caffeine makes you sleepy. Why is that? You may have developed a caffeine tolerance and no longer get the side effects that typically come with caffeine intake.
A 2019 study published in PLOS One found that ingestion of caffeine helped to increase aerobic cycling power compared to individuals who were receiving a placebo. The kicker though is that the caffeine energizing effects begin to decrease progressively from the first day as participants continued to get caffeine for 20 consecutive days. This suggests that tolerance to caffeine can form as you continue to consume caffeine.
Is sleeping after drinking coffee bad?
Even though coffee seems like an A.M. drink, it’s not uncommon to brew up a cup later in the day. Unfortunately doing this can be one of the culprits behind why you feel sleepy after coffee.
According to the Sleep Foundation, drinking coffee too close to bedtime can cause issues with circadian melatonin rhythms. These rhythms are physiological patterns that perform on a 24-hour clock, such as our sleep-wake cycle. They continue to function properly based on the normal day and night cycle (light and dark) as well as internal processes. Remember our previous discussion about adenosine? Well adenosine is an internal contributor to this rhythm since it helps to develop that sleepy feeling. Since caffeine blocks adenosine, it then can disrupt the circadian rhythm and your sleep quality.
One particular part of your sleep that is impacted is your slow-wave sleep. The National Institute of Health states slow-wave sleep is the deep sleep you need in order to wake up feeling refreshed in the morning. With caffeine interrupting this important sleep stage you’re likely to still feel tired, even after drinking an energizing cup of coffee.
According to a 2013 study published in the Journal of Clinical Sleep Medicine even drinking caffeinated beverages 6 hours before bed could reduce sleep time by up to 1 hour. The kicker was that participants were not aware that their sleep was impacted when drinking coffee 6 hours before going to sleep but noticed sleeping problems when they had caffeine 0 to 3 hours before bed.
How to minimize these effects?
If you’re not ready to part with your intake of coffee, there are some changes you can make in order to avoid being tired after drinking coffee.
First off, it’s important to stick with the recommended intake of caffeine each day. Mayo Clinic states that 400 mg of caffeine each day is a safe amount for adults which equals about 4 cups of coffee.
Other recommendations include:
1. Limiting sugar in coffee: Decreasing or eliminating sugar in your coffee will prevent those blood sugar spikes which can lead to tired feelings. If you don’t enjoy coffee without a hint of sweetness, you could also consider sugar alternatives which typically don’t create blood sugar spikes like normal sugar.
2. Drinking water: Staying hydrated is important to prevent dehydration which leads to feeling tired. Pair your cup of coffee with a glass of water, or just be sure to drink plenty of water throughout the day. A general rule of thumb, according to Mayo Clinic, is that men should have about 15.5 cups of fluid per day while women need around 11.5 cups. This fluid recommendation includes water, other beverages, and food (although food only provides 20% of daily fluid intake). Moreover, drinking adequate water can also help overcome laziness and stay energetic throughout the day.
3. Not having that afternoon coffee: As we mentioned previously, drinking coffee too close to bedtime can result in less sleep. Don’t enter the vicious cycle of sleep deprivation and leave your coffee intake to the mornings.
Although we’re usually prepared to feel a burst of energy after having a cup of coffee, that’s not always the case. Since caffeine can impact processes in the brain, disrupt sleep, and even become tolerated after consistent intake, that energizing feeling may be short-lived and turn to sleepiness. It is because of this that you end up thinking ‘Why does coffee make me feel sleepy?’
While we have already answered your question of why coffee makes me tired, to further prevent feeling like you need a nap after coffee, stick with the recommended daily intake of caffeine and limit the amount of sugar you may use. It’s also important to stay hydrated throughout the day with water and avoid drinking coffee too close to the time you plan to hit the hay.