How Much Caffeine Is Too Much?

Caffeine is a normal part of many people's day, whether you're waking up to a cup of coffee or drinking a soda in the middle of the day. But how much caffeine is too much, and can it be harmful?

According to one study, about 85% of the U.S. population has at least one caffeine-containing beverage per day, with an average of 165 milligrams of caffeine consumed daily.

Caffeine can be part of a healthy diet for most people. However, too much may be dangerous for your health. This article discusses how much caffeine you should have in a day. It also covers the signs and symptoms when you overindulge in caffeine and how to reduce your intake.

Symptoms of Too Much Caffeine - Illustration by Theresa Chiechi

Verywell / Theresa Chiechi

How Much Daily Caffeine Is Too Much?

According to the U.S. Food and Drug Administration, adults should not consume more than 400 milligrams (mg) of caffeine a day. This comes out to about four or five cups of coffee.

There are no official FDA recommendations for how much caffeine children and teenagers should consume. However, Canada recommends that children and adolescents (up to 18 years) should not consume more than 2.5 mg per kilograms (kg) of body weight.

Under these guidelines, a child that weighs 50 kg (112 pounds) should have no more than 20 mg of caffeine per day. Keep in mind that one can of cola has about 36 to 46 mg of caffeine.

Some people are more sensitive to the effects of caffeine than others. If you experience symptoms of too much caffeine, then you should reduce your intake.

How Much Caffeine Is in This?

Food and drinks can vary in the amount of caffeine they have. Here are approximate amounts per item:

  • 12 ounces (oz) of caffeinated soft drink: 30-40 milligrams (mgs)
  • 8 ounces of green or black tea: 30-50 milligrams
  • 8 ounces of coffee: 80-100 milligrams
  • 8 ounces of decaf coffee: 2-15 milligrams
  • 8 ounces of energy drink: 40-250 milligrams
  • 1 ounces of dark chocolate: 12 milligrams

These are averages. Always read the label to make sure you aren't consuming more caffeine than intended.

Symptoms of Too Much Caffeine

When caffeine intake exceeds a healthy amount, it may lead to side effects. Symptoms of too much caffeine include the following:

  • Headache
  • Anxiety
  • Trouble sleeping
  • Irritability
  • Increased heartbeat
  • Increased thirst
  • Frequent urination
  • Chest pain

Headache

Caffeine is a commonly used psychostimulant, meaning it's a substance that stimulates the central nervous system. This is why many people drink coffee or caffeinated tea as a morning pick-me-up. In some cases, caffeine is used as a form of pain relief, such as in the pain medicine Excedrin, which contains aspirin, paracetamol, and caffeine. However, both consuming too much caffeine and withdrawal from caffeine can cause headaches.

Caffeine can trigger what is known as "caffeine rebound." This means that after you drink a lot of caffeine, you may experience withdrawal symptoms after the initial benefits have worn off. Overall, the National Headache Foundation says that it's fine to consume caffeine in moderation. However, it's best to avoid daily use if you are experiencing frequent headaches.

Anxiety

Caffeine may affect your mood. While moderate caffeine intake can contribute to feelings of happiness, having two to six cups of caffeine can bring on anxiety. Anxiety is a feeling of being wound-up, restless, or on edge.

A review of 57 studies measured the effects of anxiety after consuming various amounts of caffeine. Results were mixed when it came to both low and high intakes. Some research showed having up to five cups of coffee had no effect on anxiety. Other studies found feelings of tension after consuming just two or three cups.

Whether you feel anxiety at low or high levels, it could indicate that you are having too much caffeine and may want to scale back.

Trouble Sleeping

When consumed close to bedtime, caffeine may cause mild sleep disturbances at moderate and high doses. Consuming caffeine before bed can reduce the quantity and quality of sleep and make it harder to fall and stay asleep. It is recommended to not have caffeine up to six hours before bed.

However, if you regularly consume caffeine, its effects won't be as detrimental to your sleep over time. Your body can adjust to the effects of caffeine and build up a tolerance over time. 

Irritability

Consuming caffeine can also contribute to feelings of irritability, but this has mostly been observed in people who consume a lot of it. However, if you have an existing psychological or anxiety disorder, you may experience irritability with less caffeine consumption than the average person.

Although more research needs to be done to find exactly how much caffeine leads to irritability, you may want to scale back if you get angry or agitated after consuming caffeine.

Increased Heartbeat

Caffeine has different effects on the heart. Some research found as little as four cups of coffee could cause mild changes in heart rate. Another small study found consuming five cups of coffee did not affect heart rate in people with heart disease.

This may be due to how well the body can break down caffeine. Slow caffeine metabolizers were more at risk for heart issues after just two or three cups of coffee. While those who cleared caffeine from their system quickly had fewer issues when consuming the same amount of caffeine.

A rapid heartbeat can also signify a caffeine allergy, sensitivity, or another health issue. Cutting back or eliminating caffeine is recommended if caffeine affects the heart.

Increased Thirst

Research shows even low intakes of caffeine may increase thirst in some people. Thirst was most notable to casual caffeine consumers even just after one cup of coffee. Those with daily caffeine intake were unable to detect thirst at this level.  

There is no evidence of how high caffeine consumption affects thirst. However, it is possible that being thirsty could be due to high levels of caffeine.

Frequent Urination

Caffeine is a diuretic. This is a substance that increases the production of urine and makes you have to pee. Caffeine can increase blood flow to the kidneys and directly affects their ability to reabsorb salt and water as they filter the blood, leading to an increase in urine in the bladder. People with an overactive bladder may be more susceptible to the diuretic effect of caffeine.

Along with the loss of urine also goes important nutrients. One study found that having about four cups of coffee caused reductions in thiamin, B12, calcium, magnesium, sodium, phosphate, chloride, and potassium. This could have a negative effect on bone health.

While it is ultimately unknown how higher intakes of caffeine affect the bladder, the frequent need to pee could indicate too much caffeine or another condition.

Chest Pain

Chest pain occurs when blood flow to the heart is blocked. As caffeine increases, so do the restrictions in blood flow. Therefore, too much caffeine may cause chest pain. However, the caffeine needed to cause chest pain is generally a very high amount, so overall the risk is low if you are only consuming one to three cups a day.

Those with health conditions, who are on medications, and/or are caffeine sensitive may experience decreased blood flow and chest pains with less than two cups of coffee. If you have chest pains after consuming caffeine, it could indicate a serious problem. Be sure to seek medical help right away.

Allergic Response to Caffeine

If consuming caffeine results in problems breathing, you could have a caffeine allergy. If this happens, stop consuming it right away and seek medical help. Call 911 if you are experiencing symptoms of anaphylaxis, including trouble breathing, hives, low blood pressure, and a pale skin color.

Caffeine and Medications

Caffeine intake may interfere with the effectiveness of medications and alter how they work. The following medications are affected by caffeine intake:  

  • Antidepressants
  • Sedatives
  • Antipsychotics 
  • Blood pressure drugs
  • Anticoagulants
  • Alzheimer's and Parkinson’s drugs 
  • Cancer medications
  • Thyroid medications
  • Antibiotics
  • NSAIDs
  • Migraine medications
  • Estrogen
  • Oxandrolone

Ask your doctor how caffeine may interact with your medications so you can avoid absorption problems.

Caffeine Can Affect How Medications Work

Caffeine may increase or decrease how much medication is absorbed. This can alter the effects of the drug. Ask your healthcare provider to learn how caffeine may interfere with your medications.

Tips to Reduce Caffeine Intake

Reduce caffeine intake with these tips:

  • Switch to low or no caffeine: Reduce caffeine intake by replacing foods and beverages that have little to no caffeine. To avoid caffeine withdrawal, start by reducing caffeine intake first. For example, try ordering half-caf coffee (coffee that is half caffeinated and half decaf) or switching your second cup of tea to herbal.
  • Drink more water: Drinking more water will fight fatigue and improve mood and energy levels.
  • Eat more foods with nutrients: Vitamin C, iron, magnesium, zinc, fiber, and the B complex vitamins may improve fatigue. These are found in milk, cheese, eggs, liver, poultry, organ meat, tuna, mackerel, salmon, clams, nuts, seeds, whole grains, and colorful and leafy green vegetables.

How Long Does It Take For Caffeine to Wear Off?

According to the FDA, caffeine has a half-life of about four to six hours. This means that up to six hours after you consume caffeine, at least half of the caffeine is still present in your body.

Summary

Caffeine is a natural stimulant that alters brain and body function. A majority of the population consumes at least one caffeinated beverage daily, mostly in the form of coffee, tea, and soda.

Moderate caffeine consumption has been associated with improvements in energy, mood, weight, cognition, and physical performance. However, too much caffeine may cause headaches, anxiety, trouble sleeping, irritability, respiratory issues, chest pain, thirst, and frequent urination.

Certain people may be more sensitive to caffeine and may see these effects at even lower doses. Caffeine may cause allergies, and alter the effects of certain medications.

If you find that caffeine leaves you with side effects you may want to limit or avoid caffeine altogether. Increasing your intake of water and nutrient and fiber-rich foods, such as vegetables, nuts, and seeds, may also help to reduce caffeine intake.

A Word From Verywell

Caffeine can affect everyone differently. If you are experiencing discomfort with caffeine intake, reducing your consumption may help. Depending on how much caffeine you normally take in, quitting cold turkey may cause some withdrawal symptoms. Slowly cutting back can help keep these symptoms at bay. Talk to your doctor if you're concerned about how caffeine is affecting you.

Frequently Asked Questions

  • How much caffeine is in one cup of coffee?

    Caffeine levels vary depending on the size and type of coffee. An 8 ounce (oz) cup of brewed coffee has about 96 milligrams (mg) of caffeine. An 8 ounce cup of instant coffee has 62 milligrams of caffeine. A one-shot (1 ounce-1.75 ounces) cup of espresso contains between 63-110 milligrams of caffeine. Coffee cups range from 8-31 ounces. Bigger cups will contain more caffeine.

  • How much caffeine is in one cup of green tea?

    An 8-ounce cup of green contains 30-50 milligrams of caffeine.

  • Is drinking too much coffee bad for you?

    Intakes over 400 milligrams of caffeine a day have been associated with insomnia, jitters, anxiousness, a fast heartbeat, upset stomach, headache, and a sad mood. It may also increase the risk of male infertility, cancer, heart disease, mood disorders, and weakened bones.

  • How can you eliminate caffeine from your body?

    The way to eliminate caffeine is to wait it out. It takes about 3 to 6 hours for caffeine to leave the body.

  • How can you go to sleep after having too much caffeine?

    The only thing that can improve sleep is letting caffeine leave your system.

  • How much caffeine can you have while pregnant?

    If you are pregnant, trying to get pregnant, and/or are breastfeeding you should limit your caffeine intake to less than 200 milligrams a day (about one and a half 8-ounce cups).

  • How much caffeine can you have for pre-workout?

    Doses between 1.4 and 2.7 milligrams per pound of bodyweight worked best when taken 60 minutes before exercise.

  • Is decaf coffee really caffeine-free?

    No, there is still caffeine in decaffeinated coffee. An 8-ounce cup of decaf coffee has about 2-15 milligrams caffeine.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Jeanette Kimszal, RDN
Jeanette found a passion for health and wellness after her own transformation. This led to the pursuit of becoming a Registered Dietitian Nutritionist (RDN) in 2015. As an RDN, Jeanette uses her journalism and nutrition education to create evidence-based health content.