Energy Management 10 MIN READ

Caffeine’s Impact On Blood Glucose

The world was already a great admirer of the beverage even before the deluge of international coffee chains. The hot, fragrant brew evokes a familiar sense of comfort everywhere in the world. It is perhaps one of your favourite beverages too.

Written by Team Ultrahuman

May 21, 2022
Caffeine Impact BloodGlucose

The world was already a great admirer of the beverage even before the deluge of international coffee chains. The hot, fragrant brew evokes a familiar sense of comfort everywhere in the world. It is perhaps one of your favourite beverages too.

But is that love reciprocated?

Let’s understand what happens in the body when you consume caffeine and its impact on blood glucose. Tea, coffee, cola, energy drinks – what’s the common denominator? Caffeine.


  • Coffee contains caffeine which is a bioactive compound and is a central nervous system stimulant,
  • Caffeine has also been linked with adverse effects like rapid heart rate, sleep disturbances, and anxiety,
  • It lowers your insulin sensitivity which leads to insulin resistance. 

What is Caffeine?

Caffeine is a natural, central nervous system stimulant of the methylxanthine class. In small doses, it is known to increase alertness. In its purest form, caffeine is a bitter white powder.

Caffeine was first extracted and isolated from coffee in 1819. It is also found in tea, and cacao pods, resulting in cocoa and chocolate products. Commonly consumed beverages such as cola drinks also contain caffeine, having been sourced from kola nuts. 

It is the world’s most widely consumed psychoactive drug. 80% of the world’s population consumes a caffeinated product daily. The global coffee market was priced at USD 102.15 Billion in 2019. So you can imagine how coffee has become an indelible part of our daily lives. 

Why Do People Consume Caffeine? 

When most people think of coffee, they picture it as a booster. Some people consider it to be a healthy drink. The most common uses of caffeine are for mental alertness, headache, migraine, athletic performance, memory, and obesity.

Many of us rely on a morning cup of coffee to help us get through the day and improve our mood.

Athletes use caffeine as their stimulants. Some people consume caffeine by mouth to address conditions like gallbladder disease, attention deficit-hyperactivity disorder (ADHD), and asthma but there is a lack of enough scientific evidence to support these uses.

How does Caffeine Keep you Awake? 

Keeping that in mind, it’s interesting to break down how coffee works in our bodies. One of the most common functions is to delay the onset of drowsiness and to stay alert. What does this look like in the body?

1. Caffeine increases blood adrenaline levels

Caffeine may increase blood adrenaline levels and increase brain activity of the neurotransmitters dopamine and norepinephrine.

Adrenaline enhances productivity since its functions include increasing the heart rate, increasing blood pressure, expanding the air passages of the lungs, enlarging the pupil in the eye, and redistributing blood to the muscles.

This alters the body’s metabolism, so as to maximize blood glucose levels (primarily for the brain) all leading to sharper focus. 

2. Dopamine

Dopamine is a neurotransmitter that activates pleasure centers in certain parts of the brain. It’s also the brain chemical responsible for your happiness and engagement with the outside world.

A study suggests that drinking a moderate amount of coffee reduced some study participants’ risk of depression and suicide

3. Hormone Melatonin

Caffeine may keep you awake even if you don’t want it to. Levels of the hormone melatonin, which your body needs to fall asleep, decrease in the presence of caffeine.

The brain naturally contains the chemical adenosine — which is responsible for making us feel tired — and norepinephrine, a stimulant.

When unaffected by caffeine, the brain has a certain amount of receptors for each of these chemicals to bind to in order to maintain the body’s normal cycle of lethargy and alertness.

4. Productivity

Caffeine plays a clear role in productivity in that daily consumption can lead to periods of wakefulness and alertness that enhance cognitive function. It raises energy levels and perks up your mood.

How does Caffeine Affect the Body?

Caffeine and Adenosine Receptors

Our neurons break down a high-energy molecule called adenosine triphosphate. One of these breakdown products is adenosine.

Adenosine levels increase in neurons as the brain consumes energy over the course of the day. Some of this adenosine escapes the neurons and binds to the adenosine receptors.

When adenosine binds to its receptors, neural activity slows down and  induces sleep

Adenosine is a central nervous system neuromodulator. The stimulant effect of coffee comes primarily from the way it acts on the adenosine receptors in the neural membrane. 

Caffeine tricks the brain by competing with adenosine receptors which otherwise send signals to your nervous system to slow down when you’re tired.

Caffeine reduces the sensitivity of the neurons to adenosine and makes you alert. Depending on how swiftly your body metabolizes caffeine, its effect is rather short-lived.

Once the body breaks down caffeine, adenosine easily binds to the receptors. Hence it is followed by a  “crash” a few hours later.

Caffeine interrupts sleep signals by blocking the action of adenosine, a temporary reprieve from drowsiness and fatigue is experienced but can affect night sleep if consumed too close to bedtime (less than 8 hours before bed).

New research has shown that coffee consumption can suppress the production of melatonin produced by the pineal gland. 

Caffeine alters the activity of these receptors, largely because of its close resemblance to adenosine. Once caffeine enters the brain, it is recognized by brain receptors as adenosine and is able to bind to the adenosine receptors.

Through this process, caffeine essentially stops adenosine from locking into the brain’s receptors and slows down nerve cell activity.

In turn, the sudden increase in brain activity triggers the adrenal glands to produce more adrenaline.

After long-term exposure to caffeine, the brain increases the production of adenosine and decreases the production of the stimulant norepinephrine to maintain equilibrium with the caffeine intake.

Caffeine’s ability to alter the brain’s chemical production is the root cause of both its beneficial and adverse effects on the body.

Sports performance and exercising are improved with caffeine through three mechanisms – blocking adenosine and increased release of muscle calcium.

This enhances sports performance since athletes are more prone to losing calcium, as well as other minerals, through perspiration, and effects on catecholamines which help the body respond to stress or fright and prepare the body for “fight-or-flight” reactions.

It also leads to more energy available for exercise

However, the effect of this might differ according to sexes. According to Effect of Caffeine Supplementation on Sports Performance published on NCBI, the ergogenic (increasing capacity for bodily or mental labor especially by eliminating fatigue symptoms) of caffeine for anaerobic performance (any activity that breaks down glucose for energy without using oxygen) was higher in men than women.

Research suggests that there are quite a few negative effects of the consumption of coffee too. It can cause jitters which can increase anxiety and insomnia issues and it also elevates your blood pressure- especially during or right after exercise or any other physical activity. 

It can cause an irregular heartbeat and prevents calcium absorption in the bones which can risk making your bones brittle as you age. Studies suggest that the mean half-life of caffeine in the plasma of healthy individuals is about 5 hours.

However, its elimination half-life may vary between 1.5 and 9.5 hours. 

What does that mean? In the case of consumption of 10 milligrams (mg) of caffeine, you’ll still have 5 mg of caffeine in your body after 5 hours. The effects of caffeine reach peak levels within 30 to 60 minutes of consumption.

Coffee’s Impact on Blood Glucose 

The effects of coffee on blood glucose levels have been studied for a long period of time and studies show that an exaggerated rise in blood sugar levels is noted following a meal i.e., known as postprandial hyperglycemia (elevated blood sugar levels). 

After eating, blood sugar levels rise. Insulin released by the pancreas helps the cells to absorb blood sugar for energy and storage. With this absorption, glucose levels in the bloodstream begin to decline.

The pancreas then produces glucagon, a hormone that prompts the liver to release stored sugar. This interaction of glucagon and blood sugar ensures stable blood glucose levels in the body and the brain.

The impact of caffeine on glucose levels is that it affects how your body responds to insulin. Caffeine may lower your insulin sensitivity. When insulin sensitivity is reduced, insulin resistance sets in. That means your cells don’t react to the hormone as much as they once did.

They don’t absorb as much sugar from your blood after you eat or drink. This causes your body to make more insulin, so you have higher levels after meals. 

  1. Caffeine raises levels of certain stress hormones, like epinephrine (also called adrenaline). Epinephrine can prevent your cells from processing as much sugar. It may also keep your body from making as much insulin.
  2. It blocks adenosine which plays a big role in how much insulin your body makes. It also controls how your cells respond to it. 
  3. Too much caffeine can compel you to stay awake. Lack of sleep may also lower your insulin sensitivity.

Coffee consumption arbitrates (activates contractions in the gut while other elements stimulate the production of stomach acid) the levels of gut peptides hormones that regulate satiety and insulin secretion.

A study found that drinking more than 3 cups of coffee a day could lead to hypoglycemia and hyperglycemia. Hypoglycemia is the deficiency of glucose in the bloodstream and hyperglycemia occurs when blood sugar levels are too high.

The reason this happens is that the caffeine content found in coffee gives you an instant burst of energy but also causes blood sugar levels to drop soon after. 

According to the research, people who drink coffee have a higher tendency to have hypoglycemia. In contrast, there is a lower risk of hyperglycemia in coffee drinkers.

This is because caffeine speeds up the body’s metabolism and insulin resistance decreases. But this does not mean that people should drink more coffee than they already do.

Recommendation of Ideal Coffee[Caffeine] Intake

According to the FDA, about 4-5 cups of coffee (400 milligrams of caffeine) doesn’t affect healthy adults. However, its actual digestion varies from person to person. 

In case you’re particularly sensitive to caffeine, you may want to avoid decaf beverages as well since they do contain trace amounts of caffeine. 

The timing of consumption also matters. These findings recommend refraining from substantial caffeine use for a minimum of 6 hours prior to bedtime.


To sum up, the effects of caffeine are specific to each individual. Some of the biggest benefits of light-to-moderate caffeine are related to enhancing productivity and increasing alertness. Coffee contains caffeine which is a bioactive compound and is a central nervous system stimulant. Caffeine has also been linked with adverse effects like rapid heart rate, sleep disturbances, and anxiety. It lowers your insulin sensitivity which leads to insulin resistance. 

For most young, healthy adults, caffeine doesn’t appear to noticeably affect blood sugar (glucose) levels, and having up to 400 milligrams a day appears to be safe. 

The timing of caffeine is also important as it may disrupt sleep. While caffeine stays in the body for different durations for each individual, it is generally recommended to consume caffeine between late morning to early afternoon.

Avoid caffeinated beverages post 4-5 pm.

If you have underlying health concerns or are concerned about your blood sugar levels, limiting the amount of caffeine may be the right move for you.

Disclaimer: The contents of this article are for general information and educational purposes only. It neither provides any medical advice nor intends to substitute professional medical opinion on the treatment, diagnosis, prevention, or alleviation of any disease, disorder, or disability. Always consult with your doctor or qualified healthcare professional about your health condition and/or concerns before undertaking a new health care regimen including making any dietary or lifestyle changes.


  1. Caffeine (1, 3, 7‐trimethylxanthine) in Foods: A Comprehensive Review on Consumption, Functionality, Safety, and Regulatory Matters – Heckman – 2010 – Journal of Food Science – Wiley Online Library
  2. Global Coffee Market – By Product: Global Industry Perspective, Comprehensive Analysis and Forecast 2020 – 2026.
  3. CAFFEINE: Overview, Uses, Side Effects, Precautions, Interactions, Dosing, and Reviews
  4. An update on the mechanisms of the psychostimulant effects of caffeine
  5. Caffeine and Dopamine

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