Caffeine is a substance that stimulates the body’s central nervous system, helping you feel more awake and giving you a boost of energy. It comes from natural sources like coffee beans, cacao, and tea leaves, and is commonly added to foods, drinks, and medications.

Many people consume at least one caffeinated beverage daily, and some are more sensitive to caffeine than others. This means they experience intense or unwanted side effects after relatively low doses of caffeine, such as headache, restlessness, dizziness, or trouble sleeping.

This article provides an overview of caffeine sensitivity and reasons why the stimulant affects people differently.

What Is Caffeine Sensitivity?

Moderate caffeine consumption is linked to feeling more awake, alert, and energetic. Caffeine sensitivity refers to how strongly a person feels those impacts after consuming it.

For example, drinking a cup of coffee in the morning may be way too much for one person, while another person may need three or four cups of coffee to experience caffeine’s effects.

While there’s no specific test to measure caffeine sensitivity, experts have loosely defined it into three categories based on how the body metabolizes (processes) caffeine.

Normal Sensitivity

Most people likely fall into the category of normal caffeine sensitivity. It means they’re able to consume up to 400 milligrams of caffeine (roughly four to five cups of coffee) without experiencing negative side effects. This amount is the Food and Drug Administration’s (FDA’s) recommended daily caffeine intake limit and appears to be safe for most healthy adults.

Hyposensitivity (Low Sensitivity)

People with low sensitivity to caffeine can take in even higher doses of caffeine without experiencing negative side effects. They can also usually consume caffeine before bed without having any sleep disruptions.

For people in this group, the body metabolizes (processes) caffeine quickly. One study estimates that roughly 10% of the population carries a gene linked to low caffeine sensitivity.

Hypersensitivity (High Sensitivity)

People with a high caffeine sensitivity metabolize the stimulant more slowly.

Having a high or heightened sensitivity to caffeine means you likely experience an intense reaction to small doses of caffeine, such as:

  • Insomnia
  • Increased heart rate
  • Restlessness
  • Headache

In this group, one cup of coffee may feel like four cups, and can cause issues falling asleep at night.

Symptoms

When caffeine is consumed in moderation, its desired effects can include mood enhancement, alertness, improved focus, and quicker processing times.

Difference Between Caffeine Sensitivity, Allergy, and Tolerance

The following terms are sometimes used interchangeably, but they’re not the same:

  • Caffeine sensitivity refers to how the body processes caffeine, due, in large part, to genetics.
  • A caffeine allergy is an extremely rare immune system response that can cause potentially severe symptoms such as a rash, hives, or trouble breathing. A healthcare provider can test you for a caffeine allergy.
  • Caffeine tolerance describes how the body responds to caffeine over time. A tolerance develops when the desired effects of caffeine eventually decrease with regular consumption.

But when caffeine intake exceeds a person’s sensitivity level, it can lead to unwanted side effects. These can develop as soon as several minutes after consuming it. They include:

  • Headaches
  • Anxiety
  • Dizziness
  • Rapid or irregular heartbeat
  • Restlessness and shakiness
  • Insomnia (trouble sleeping)
  • Diuresis (increased urination)
  • Upset stomach
  • Muscle twitching
  • Flushed face

Diagnosis

There’s currently no medical test to check for caffeine sensitivity. But if you’re planning on speaking to a healthcare provider about your caffeine intake and sensitivity level, it may be worth monitoring at home by:

When to Call a Healthcare Provider

Caffeine sensitivity symptoms may be unpleasant, but they usually aren’t harmful or severe. They typically go away when caffeine intake is reduced. Check with a healthcare provider if your symptoms are concerning or interfering with your daily life.

  • Keeping a daily log of food, drink, and medication intake to determine if you may actually be taking in more caffeine than you realize.Checking labels closely on food products, drinks, and medications, as caffeine is sometimes included in many less-obvious items.Slowly and carefully reducing your caffeine consumption for a few days to see if this affects your symptoms, which could help reveal if caffeine sensitivity is truly the cause.

Common Causes

Experts have found that several factors can play a role in determining how your body reacts to caffeine.

Caffeine Withdrawal

Keep in mind that if your body is used to caffeine, suddenly reducing or eliminating your intake can prompt caffeine withdrawal symptoms, such as headaches, drowsiness, and irritability. It’s a good idea to check with a healthcare provider before cutting anything completely out of your diet.

Liver Metabolism

Caffeine is metabolized (broken down) in the liver by an enzyme (protein) known as CYP1A2. The gene associated with this enzyme helps predetermine how sensitive a person may be to caffeine consumption. Studies have found people with a high caffeine sensitivity don’t produce as much CYP1A2.

Medications

Some medications and supplements can interact with caffeine sensitivity. This can make caffeine side effects more intense.

Research suggests that a medication used to treat asthma known as theophylline, and echinacea, an herbal supplement thought to help cold symptoms, can increase the effects of caffeine in the body.

Check with a healthcare provider or pharmacist if you think medications may be interfering with how your body processes caffeine.

Genetics

Research has shown that a person’s genetic makeup has a lot to do with how they respond to caffeine.

In addition to the CYP1A2 gene that influences how quickly the liver breaks down caffeine, another gene known as ADORA2A impacts how the central nervous system (communication between the brain and body) reacts to caffeine’s stimulating effects. People who have a variation of the ADORA2A gene are likely to have a high sensitivity to caffeine that affects their sleeping pattern.

Risk Factors

Caffeine sensitivity varies greatly by individual. But in general, there are several factors that can potentially make a person more susceptible to high caffeine sensitivity. These include:

  • Older ageFemale sexCertain chronic health conditionsSmokingOral contraceptive (birth control) use

For most healthy adults, the FDA recommends no more than 400 milligrams of caffeine a day, which equals about four or five cups of coffee. That’s the amount that the agency has found is generally not associated with any negative health effects.

There are no current federal recommendations on caffeine intake for children or adolescents. Experts generally discourage caffeine consumption in those ages 12 and younger, and suggest a very limited caffeine intake in those ages 12–18.

Caffeine Alternatives

Frequent caffeine consumption may lead to a physical or psychological dependence on it.

Caffeine Use in Pregnancy

It’s recommended that pregnant people limit caffeine intake to less than 200 milligrams per day. Any more caffeine than that has the potential to negatively impact the pregnancy and developing child.

If coffee is part of your daily ritual, and you’re looking to replace it with a lower caffeine or caffeine-free option, consider the following alternatives:

  • Yerba mate tea
  • Matcha tea powder
  • Chai tea
  • Chicory root coffee
  • Maca root powder
  • Dandelion root tea
  • Warm lemon water
  • Herbal or rooibos tea
  • Smoothies
  • Golden milk (made with milk and spices like turmeric)
  • Carob powder (a replacement for cacao powder)
  • Cordyceps (a fungi that is regarded as an energy booster)

Keep in mind that there is still some caffeine in decaffeinated coffee. An 8-ounce cup of brewed decaf coffee can have anywhere from 1 to 25 milligrams of caffeine. Chai tea and Matcha tea powder also contains caffeine, just not as much as is in coffee.

Summary

Caffeine is a stimulant that acts on the body’s central nervous system. While it’s usually linked to improved energy, cognition, and mood, consuming too much can interfere with sleep, make you feel restless, and even affect your heart rate.

Some people are more sensitive to caffeine than others and experience negative effects even at very low doses. Research shows that genetics play a large part in how the body processes the stimulant, which determines a person’s caffeine sensitivity. Though they may be unpleasant, caffeine sensitivity symptoms usually aren’t harmful and can be addressed by reducing or eliminating caffeine.

A Word From Verywell

Caffeine affects everyone differently, no matter which caffeine sensitivity category you fall in. If you’re experiencing any discomfort with your daily caffeine intake, slowly reducing your consumption can help. Check with a healthcare provider or other trusted community health source if you have concerns about how caffeine may be affecting you.

Frequently Asked Questions

  • Is caffeine bad for you?
  • For most people, daily caffeine consumption is generally considered to be safe. Some studies show that caffeine in moderation may have several health benefits on the brain and body, but taking in too much can cause unwanted side effects and interact with medications. Check with a healthcare provider to make sure caffeine is safe for you to consume.
  • Learn More:
  • What Is Caffeine? Is It Good for You?
  • Can you develop caffeine sensitivity or are you born with it?
  • Caffeine sensitivity is largely determined by genetics, so you’re mostly stuck with the sensitivity level that you’re born with. That said, it is possible for caffeine sensitivity to fluctuate slightly throughout life based on aging and other lifestyle factors.
  • How do you get rid of caffeine sensitivity?
  • You can’t change caffeine sensitivity, but you can build up a caffeine tolerance. A caffeine tolerance refers to how your body reacts to the stimulant over time. Caffeine will likely have a stronger effect on people who haven’t been consuming it regularly.

For most people, daily caffeine consumption is generally considered to be safe. Some studies show that caffeine in moderation may have several health benefits on the brain and body, but taking in too much can cause unwanted side effects and interact with medications. Check with a healthcare provider to make sure caffeine is safe for you to consume.

Caffeine sensitivity is largely determined by genetics, so you’re mostly stuck with the sensitivity level that you’re born with. That said, it is possible for caffeine sensitivity to fluctuate slightly throughout life based on aging and other lifestyle factors.

You can’t change caffeine sensitivity, but you can build up a caffeine tolerance. A caffeine tolerance refers to how your body reacts to the stimulant over time. Caffeine will likely have a stronger effect on people who haven’t been consuming it regularly.