Caffeine is a popular stimulant. However, some people may experience caffeine sensitivity, which can cause nausea, anxiety, and trembling after consuming low amounts of caffeine.

Different people experience different effects when consuming caffeine, and they may have different levels of tolerance to it. For example, some people can comfortably consume the equivalent of four cups of coffee, while others may feel side effects after just two cups.

This article looks at the symptoms and causes of caffeine sensitivity. It also discusses how to manage caffeine sensitivity and how much caffeine is too much.

a man with a headache due to Caffeine sensitivityShare on Pinterest
A person with caffeine sensitivity may experience anxiety, trembling, and jitteriness when they consume it.

For people with a caffeine sensitivity, consuming low amounts may cause the same side effects that most people experience at high doses.

High doses of caffeine can cause:

  • nausea
  • anxiety
  • trembling
  • jitteriness

People who consume a lot of coffee may also experience:

  • insomnia
  • a rapid heartbeat
  • headaches
  • a low mood
  • increased blood pressure

Health professionals do not yet have a specific test to check for caffeine sensitivity.

People who suspect that they have a sensitivity may wish to stop or reduce their consumption of caffeine. Many foods, beverages, and medications contain caffeine, so people should read product labels very carefully.

People can try consuming small but increasing doses of caffeine to determine at what amount their symptoms start. If reducing or limiting caffeine does not resolve these symptoms, sensitivity is not the cause, and the person should consult a doctor.

Some people are sensitive to the anxiety-promoting effects of caffeine, while others are more sensitive to caffeine-induced insomnia or sleep disturbances. People with anxiety or panic disorder may experience a worsening of their symptoms after consuming caffeine.

Some researchers suggest that the cause of caffeine sensitivity may occur at the receptor level, where caffeine binds, or at the level of metabolism. For example, some people are slow metabolizers of caffeine. This means that it takes their bodies longer to get rid of caffeine.

Other people are more sensitive to the long-term effects of caffeine. Usually, caffeine causes a temporary rise in blood pressure that disappears with repeated consumption. However, people with caffeine sensitivity may experience continued elevations in blood pressure.

Several factors may contribute to the differences in caffeine sensitivity from person to person. These factors may include:

  • genetics
  • age
  • sex
  • other drug use
  • circadian factors
  • sleep hygiene

Some people are more susceptible to caffeine sensitivity than others. For example, older adults may be more sensitive to its effects on sleep.

Some groups may wish to limit or avoid caffeine altogether to prevent complications or dangerous effects. These groups include:

Pregnant women

Most experts agree that consuming fewer than 200 milligrams (mg) of caffeine per day, which is the equivalent of one 12-ounce cup of coffee, is generally safe for most pregnant women. Other sources state that 300 mg per day is likely not associated with side effects during pregnancy.

During pregnancy, caffeine travels across the placenta, and the developing fetus cannot eliminate this substance. Therefore, the fetus relies on the woman’s kidneys to clear caffeine from its body. Pregnancy makes it harder for a woman’s kidneys to clear caffeine. As a result, pregnant women should be aware of their consumption of caffeine.

High levels of caffeine can affect the developing fetus. Women who consume a lot of coffee may cause constriction of the blood vessels supplying the placenta and increased fetal heartbeat. This can impair oxygen delivery to the growing fetus.

Children and adolescents

Some companies market caffeinated drinks to children and adolescents for a variety of purposes. Children and adolescents should not drink stimulant-containing beverages, however.

Caffeine may impact the neurological development and cardiovascular systems of young people. Children and adolescents can also develop a physical dependence on caffeine.

These groups are more at risk of unintentionally consuming higher doses of caffeine because they are usually unaware of the difference between energy drinks and sports drinks. Drinking an energy drink instead of an electrolyte sports drink may result in the ingestion of a large dose of caffeine.

Older adults

One factor that may contribute to the influence of coffee and caffeine consumption on sleep is older age. Studies have demonstrated that even when controlling for insomnia-related variables that occur with age, older adults are more sensitive to the insomnia effects of caffeine.

Compared with younger adults, middle-aged and older adults seem to be more sensitive to 400 mg of caffeine, even when there are no differences in metabolism. With age, researchers suggest that alterations to adenosine receptors contribute to worse sleep indicators.

Caffeine’s main targets are a person’s adenosine receptors. These are involved in:

  • the regulation of sleep induction
  • the effects of caffeine on sleep
  • arousal
  • the sleep-awake cycle

Aging shifts the balance of adenosine receptors in different regions of the brain, which impacts sleep and the effects of caffeine.

According to the Food and Drug Administration (FDA), healthy adults may consume up to 400 mg of caffeine per day. In most people, this amount is not generally associated with any dangerous or negative effects.

However, some people may have a higher sensitivity to the effects of caffeine than others.

For example, certain health conditions and medications can make people more sensitive to caffeine. Other people may break down caffeine slowly and feel prolonged effects after consumption.

Pregnant women, people with certain medical conditions, and those taking certain medications should consult a doctor to find out how much caffeine is safe for them.

The FDA have not set a safe dose of caffeine for children and adolescents. However, the American Academy of Pediatrics recommend that children and adolescents avoid sources of caffeine and other stimulants, especially in sports or energy drinks.

Lethal doses of caffeine tend to fall at around 200–400 mg per kilogram of body weight.

To treat caffeine sensitivity, a person should be aware of how caffeine affects their health.

For example, people who experience insomnia or anxiety may require sleeping aids or antidepressants. Instead of taking medication to treat the side effects of caffeine, they can reduce their consumption of it.

Sometimes, people with insomnia may need to avoid caffeine for a certain number of hours before sleeping. Other effects of caffeine will disappear as the kidneys remove it from the bloodstream.

In severe cases, a person may need to consult a doctor if they have consumed a toxic level of caffeine, as seizures can sometimes occur.

To cut back on caffeine, a person should reduce their consumption gradually, because the physical dependence on caffeine can cause withdrawal symptoms. Withdrawal symptoms are not dangerous, but they can be unpleasant. A healthcare provider can offer tips on how to reduce or stop caffeine consumption.

People who want to increase or boost their energy levels can choose carbohydrates and other dietary fuel sources. Energy drinks contain carbohydrates but typically contain caffeine as well.

Proper nutrition and quality sleep and sleep hygiene can boost a person’s energy levels safely and effectively.

Caffeine is present in many different foods, beverages, and medications. People with a caffeine sensitivity may wish to check all labels for hidden sources of caffeine.

Caffeine sensitivity can affect a person’s sleep, mood, and blood pressure levels, potentially causing jitteriness and nausea in some people.

If someone believes that they have a caffeine sensitivity, their doctor may recommend reducing or cutting caffeine consumption. Some people may be more at risk of side effects from caffeine, including pregnant women, children, and older adults.

To reduce caffeine intake without experiencing withdrawal symptoms, people should reduce their consumption slowly.