While coffee may increase alertness for many, it can make some people feel tired. This may be due to a tolerance to caffeine or how caffeine affects chemicals in the brain.
Caffeine does not affect everybody in the same way.
Some people, for example, can drink multiple cups of coffee during the day and experience few effects. Others may experience adverse effects after drinking a single cup of coffee.
Read on to learn more about why coffee makes some people feel tired. This article also looks at ways to manage tiredness and daily coffee intake recommendations.
Coffee itself does not make people tired, but the caffeine in coffee and its effects on the body can sometimes cause tiredness.
There are several factors that may contribute to this.
Caffeine blocks adenosine receptors in the brain
Adenosine is a brain chemical that affects the sleep-wake cycle. Adenosine levels increase during waking hours and decrease during sleep.
Usually, adenosine molecules bind to special receptors in the brain, which slows down brain activity in preparation for sleep. However, caffeine prevents this from happening by binding to adenosine receptors.
The body rapidly absorbs caffeine, so people may feel its effects within minutes. In fact, the body absorbs 99% of caffeine within 45 minutes of consuming it. Once the body fully metabolizes the caffeine, its effects will wear off.
The length of time caffeine stays in the body varies from person to person. Although it blocks adenosine receptors, it does not affect the production of new adenosine molecules.
When caffeine wears off, adenosine molecules can bind to their receptors, which can cause sleepiness.
Caffeine increases blood sugar levels
Coffee’s effects on blood sugar levels remain a point of controversy for researchers.
According to a 2018 review, caffeine can increase blood sugar levels by temporarily reducing insulin sensitivity. Hyperglycemia, or high blood sugar levels, can cause tiredness.
People with high blood sugar may also experience:
- headaches
- trouble concentrating
- increased thirst
- frequent urination
Some people build a tolerance to caffeine
People who regularly consume coffee and other caffeinated beverages can develop a tolerance to it. Since caffeine blocks adenosine receptors, the body produces more adenosine receptors to counteract the effects of frequent caffeine consumption.
In a
At the start of the study, the participants had higher heart rates and exerted greater cycling power after drinking caffeine. After 15 days, however, the effects of the caffeine began to decrease.
Given these results, it appears that people who regularly consume caffeine may build up a tolerance to its stimulant effects.
While coffee would not directly cause tiredness if a person builds up a tolerance, they may find that it no longer makes them feel as awake as it once did.
A person should speak with their doctor if they regularly experience tiredness. The doctor can help determine the underlying cause and advise on any treatments that may help.
There are also several tips that can help with managing tiredness. These include:
- consuming smaller meals more frequently rather than one or two larger meals, particularly if tiredness occurs after eating
- getting enough physical activity or exercise
- maintaining a moderate weight
- getting enough quality sleep
- avoiding caffeine before bed, as this can affect sleep
- reducing stress
- consuming enough water and staying hydrated
In general, it is best for adults to not exceed
Children under 2 years should not consume coffee or other caffeinated drinks. It is best to speak with a doctor before giving caffeine to a child older than this.
It is also best to speak with a doctor about caffeine and coffee consumption if a person is pregnant, nursing, or taking any prescription medication.
If drinking a cup of coffee makes a person feel tired, the effects of caffeine may be responsible.
Caffeine increases alertness by interfering with certain chemical processes in the brain that regulate the sleep-wake cycle. However, once the body completely metabolizes caffeine, it can make people feel tired.
The rate at which a person’s body metabolizes caffeine varies depending on genetic and lifestyle factors.
People who drink coffee every day may develop a tolerance to caffeine’s stimulant effects, which means that they need to drink more of it if they want to experience similar results.
Speak with a doctor to determine if there is an underlying cause for frequent tiredness. The doctor can advise on suitable ways to manage tiredness and recommend treatments for any condition causing the symptom.