Janet is a second-career registered dietitian (RDN) and is passionate about research and writing. Since 2015, she has been creating health and wellness content.

Chris Vincent, MD, is a practicing physician, surgeon and doctor certified by the Board of Family Medicine.

Caffeine is found in many products, including many foods and beverages. Common sources of caffeine include coffee, tea, cocoa-containing drinks, soft drinks, energy drinks, candy, chewing gum, and other packaged foods. The caffeine content of these foods and beverages varies from product to product and ranges from 50-500 milligrams (mg).

Approximately 85% of the American population drinks at least one caffeinated beverage every day. These mainly include coffee, tea and soft drinks. Other studies have shown that an average intake of 180 mg of caffeine per day.

The caffeine content of food and beverages may vary. The following is the approximate amount of each item:

These are average values. Be sure to read the label to make sure that your caffeine intake has not exceeded expectations.

Caffeine can be part of a healthy diet for most people. However, drinking more than four to five cups a day may be harmful to your health. This article discusses how much caffeine is too much. Learn about the signs and symptoms of excessive caffeine intake, and how to reduce your intake and feel better.

When caffeine intake exceeds a healthy amount, it may cause side effects. Symptoms of excessive caffeine include:

Caffeine is a commonly used psychostimulant, which means it is a substance that stimulates the central nervous system. This is why many people drink coffee or caffeinated tea in the morning to refresh themselves. In some cases, caffeine is used as a form of pain relief, such as the painkiller Excedrin, which contains aspirin, paracetamol, and caffeine. However, excessive caffeine intake and caffeine withdrawal can cause headaches.

Caffeine triggers the so-called "caffeine rebound". This means that after you drink a lot of caffeine, you may experience withdrawal symptoms after the initial benefits disappear. Overall, the National Headache Foundation of the United States stated that moderate caffeine intake is no problem. However, if you have frequent headaches, it is best to avoid daily use.

Caffeine may affect your mood. Although moderate caffeine intake can bring happiness, consuming 2 to 6 cups of caffeine can cause anxiety. Anxiety is a feeling that is coming to an end, restlessness, or nervousness.

A review of 57 studies measured the effects of anxiety after consuming different amounts of caffeine. The results of low and high intakes have been mixed. Some studies have shown that drinking up to five cups of coffee has no effect on anxiety. Other studies have found that you feel nervous after only two or three cups.

Whether your anxiety level is low or high, it may indicate that you are consuming too much caffeine and you may want to reduce your intake.

When consumed near bedtime, medium to high doses of caffeine may cause mild sleep disturbances. Ingesting caffeine before going to bed reduces the quantity and quality of sleep, and makes it more difficult to fall and stay asleep. It is recommended not to consume caffeine within six hours before going to bed.

However, if you consume caffeine regularly, over time, its effects will not cause so much harm to your sleep. Your body can adapt to the effects of caffeine and build tolerance over time.  

Caffeine intake can also cause irritability, but this mainly occurs in people who consume large amounts of caffeine. However, if you have a mental disorder or anxiety, you may feel irritable because you consume less coffee than the average person.

Although more research is needed to determine exactly how much caffeine causes irritability, if you are angry or agitated after consuming caffeine, you may wish to reduce your intake.

Caffeine has different effects on the heart. Some studies have found that as long as four cups of coffee are consumed, the heart rate will change slightly. Another small study found that drinking five cups of coffee does not affect the heart rate of heart patients.

This may be related to the body's ability to break down caffeine. With just two or three cups of coffee, people with slow caffeine metabolism are at greater risk of heart disease. Those who remove caffeine from the system have fewer problems with the same amount of caffeine.

A fast heartbeat may also indicate caffeine allergy, sensitivity, or other health problems. If caffeine affects the heart, it is recommended to reduce or eliminate caffeine.

Studies have shown that even low caffeine intake may increase thirst in some people. Even after just drinking a cup of coffee, casual caffeine consumers are most likely to feel thirsty. Those who consume caffeine every day cannot detect thirst at this level.   

There is no evidence to show how excessive caffeine consumption can affect thirst. However, thirst may be due to high caffeine content.

Caffeine is a diuretic. This substance increases the production of urine and makes you have to urinate. Caffeine can increase blood flow to the kidneys, and directly affect the kidneys' ability to reabsorb salt and water when filtering blood, resulting in an increase in urine in the bladder. People with overactive bladder may be more susceptible to the diuretic effects of caffeine.

With the loss of urine, important nutrients are also lost. A study found that drinking about four cups of coffee can cause a decrease in thiamine, B12, calcium, magnesium, sodium, phosphate, chloride and potassium levels. This may have a negative impact on bone health.

Although it is ultimately unknown how higher caffeine intake affects the bladder, the frequent need to urinate may indicate excessive caffeine or other conditions.

Chest pain occurs when blood flow to the heart is blocked. As caffeine increases, the restriction of blood flow also increases. Therefore, too much caffeine may cause chest pain. However, the amount of caffeine required to cause chest pain is usually very high, so if you only drink one to three cups of coffee a day, the overall risk is low.

Those who have health problems, are taking medications, and/or are sensitive to caffeine may experience reduced blood flow and chest pain when drinking less than two cups of coffee. If you experience chest pain after consuming caffeine, it may indicate a serious problem. Be sure to seek medical help immediately.

If ingesting caffeine causes breathing difficulties, you may be allergic to caffeine. If this happens, stop eating immediately and seek medical help. If you experience symptoms of an allergic reaction, including difficulty breathing, hives, low blood pressure, and pale skin, call 911.

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

Ask your doctor how caffeine interacts with your medications to avoid absorption problems.

Caffeine may increase or decrease the amount of medicine absorbed. This can change the effect of the drug. Ask your healthcare provider about how caffeine can interfere with your medication.

Use the following tips to reduce your caffeine intake:

According to the regulations of the US Food and Drug Administration, the daily intake of caffeine should not exceed 400 milligrams (mg). This comes out about four to five cups of coffee.

Caffeine is a natural stimulant that can change brain and body functions. Most people drink at least one caffeinated beverage every day, mainly coffee, tea and soda.

Appropriate caffeine intake is associated with improvements in energy, mood, weight, cognition, and physical performance. However, too much caffeine may cause headaches, anxiety, trouble sleeping, irritability, respiratory problems, chest pain, thirst, and frequent urination.

Some people may be more sensitive to caffeine and can even see these effects at lower doses. Caffeine may cause allergies and change the effects of certain medications.

If you find that caffeine causes side effects, you may need to limit or avoid caffeine altogether. Increasing your intake of water, nutrients, and fiber-rich foods (such as vegetables, nuts, and seeds) may also help reduce caffeine intake.

Caffeine affects everyone differently. If you feel uncomfortable with your caffeine intake, reducing your intake may help. Depending on how much caffeine you normally consume, quitting cold turkey may cause some withdrawal symptoms. Slowly reducing can help avoid these symptoms. If you are concerned about the effects of caffeine on you, please consult your doctor.

The caffeine content varies with the size and type of coffee. An 8 ounce (oz) cup of brewed coffee contains approximately 96 milligrams (mg) of caffeine. An 8-ounce cup of instant coffee contains 62 mg of caffeine. One cup (1 ounce-1.75 ounces) of espresso contains 63-110 mg of caffeine. The weight of the coffee cup is 8-31 ounces. Larger cups will contain more caffeine.

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

Daily intake of more than 400 mg of caffeine is associated with insomnia, nervousness, anxiety, rapid heartbeat, stomach upset, headaches, and sadness. It may also increase the risk of male infertility, cancer, heart disease, mood disorders and weak bones.

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

The only way to improve sleep is to let caffeine leave your system.

If you are pregnant, want to become pregnant, and/or breastfeeding, you should limit your caffeine intake to less than 200 mg per day (approximately 1 cup and a half 8 ounces).

Doses of 1.4 to 2.7 milligrams per pound of body weight 60 minutes before exercise work best.

No, decaffeinated coffee still contains caffeine. An 8-ounce cup of decaffeinated coffee contains approximately 2-15 mg of caffeine.

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