Caffeine is a fast-acting stimulant that works on your central nervous system. It can increase your blood pressure and heart rate, boost your energy, and improve your overall mood.

You may begin experiencing the effects of caffeine right after consuming it, and the effects will continue to last for as long as the caffeine remains in your body.

But how long does this last exactly? The answer depends on a variety of factors.

According to the American Academy of Sleep Medicine, caffeine’s half-life is up to 5 hours. Half-life is the amount of time it takes for a quantity of a substance to be reduced to half the original amount.

So if you’ve consumed 10 milligrams (mg) of caffeine, after 5 hours, you’ll still have 5 mg of caffeine in your body.

The effects from caffeine reach peak levels within 30 to 60 minutes of consumption. This is the time you’re most likely to experience the “jittery” effects of caffeine.

You might also urinate more due to the liquid volume being ingested and caffeine’s mild diuretic effect.

The other half of caffeine that you consume can last much longer than 5 hours.

People with caffeine sensitivities might feel symptoms for several hours or even a few days after consumption.

Due to the long-term effects of caffeine, the American Academy of Sleep Medicine recommends that you don’t consume it at least six hours before bedtime. So if you go to bed at 10:00 p.m., you should have your last round of caffeine no later than 4:00 p.m.

What food and drinks contain caffeine?

Caffeine is a natural substance found in a variety of plants, including coffee and cocoa beans, and tea leaves.

There are also artificial forms of caffeine that are commonly added to sodas and energy drinks.

Try to avoid these foods and drinks, which often contain caffeine, within six hours of your anticipated bedtime:

  • black and green tea
  • coffee and espresso drinks
  • chocolate
  • energy drinks
  • soft drinks
  • certain over-the-counter medications that contain caffeine, such as Excedrin

Decaffeinated coffee contains small amounts of caffeine, so if you’re sensitive to the effects of caffeine, you should also avoid decaffeinated coffee.

For years, experts have advised women to use caution when consuming caffeine during pregnancy. This is due to the risk of miscarriage or birth defects.

While these effects are no longer relevant after birth, there are still some cautions to consider if you plan on consuming caffeine while you’re breastfeeding.

Caffeine can be transferred through breast milk to your baby. The March of Dimes recommends limiting caffeine consumption to two cups of coffee per day when you’re breastfeeding.

If you consume other items containing caffeine throughout the day, such as soda or chocolate, you may need to cut back on the coffee and other highly caffeinated items.

Consuming more than 200 mg of caffeine a day could have unintended consequences for your baby. They might have sleeping difficulties, and they could become fussy.

Some mothers also notice colic and jitteriness in babies who are exposed to caffeine. Although these aren’t considered long-term issues, the symptoms could cause your baby discomfort.

The key to making sure your baby doesn’t experience the effects of caffeine is to plan out your consumption wisely.

According to the Australian Breastfeeding Association, your baby can consume about 1 percent of the caffeine you consume if you breastfeed.

The peak amount is reached at about one hour after you’ve had caffeine. The best time to breastfeed your baby would be before consuming a caffeinated beverage or within the first hour of caffeine intake.

Also, since the half-life of caffeine in breastmilk is about 4 hours, breastfeeding 4 hours after caffeine intake is also recommended.

If you’re used to drinking caffeine, you might experience withdrawal if you stop taking it.

According to the American Heart Association, you might experience withdrawal symptoms within 12 to 24 hours of your last caffeinated item. These symptoms may include:

  • headache (the most common symptom)
  • depression
  • anxiety
  • drowsiness and fatigue

Caffeine withdrawal symptoms tend to resolve within 48 hours. However, if you’re used to consuming large quantities, quitting cold turkey could make your withdrawal symptoms more severe.

The best way to cut out caffeine is to decrease the amount you consume every day.

You can simply reduce the number of caffeinated products you consume, or you can swap out certain items. For example, you can trade one coffee per day for green tea.

How much caffeine is in coffee and tea?

The amount of caffeine in a cup of coffee or tea is affected by many factors, such as the brewing technique, the type of beans or tea leaves, and the way the beans or leaves were processed.

BeverageCaffeine in milligrams (mg)
8-ounce cup of coffee95–165
1-ounce espresso47–64
8-ounce cup of decaf coffee2–5
8-ounce cup of black tea25–48
8-ounce cup of green tea25–29

Light roast beans have more caffeine than dark roast beans.

There’s also more caffeine in a cup of coffee than in a single serving of espresso. That means a cappuccino with 1 ounce of espresso has less caffeine than an 8-ounce cup of coffee.

Caffeine is just one way you can increase alertness and combat sleepiness. Due to the possible adverse effects, you might consider limiting your daily consumption to 300 mg a day. This equals about 3 cups of small, regular roasted coffee.

It’s also important to consider other ways you can naturally increase your energy levels without caffeine. Consider the following options to help:

  • Drink more water.
  • Get at least 7 hours of sleep per night.
  • Avoid daytime naps if you can.
  • Eat lots of plant-based foods, which may help provide energy without the crash of processed foods.
  • Exercise daily, but not too close to bedtime.

Talk to your doctor if you regularly feel tired. You may have an undiagnosed sleeping disorder.

Certain underlying conditions, like depression, can also affect your energy levels.