What Happens to Your Body When You Drink Coffee Throughout the Day

Drinking too much coffee can affect your body throughout the day and even make it harder to fall asleep at night.

From heightened alertness after your first sip to frequent bathroom trips and an afternoon crash, coffee has a distinct effect on your body and brain.

How Coffee Keeps You Alert 

Your morning cup of coffee can leave you feeling pretty buzzed. The effects can be particularly harsh if you drink multiple cups.

“Caffeine can increase heart rate, overstimulate the central nervous system, cause muscle tremors, and increase stomach acid production,” said Samantha Dieras, DCN, RD, CDN, director of ambulatory nutrition services at Mount Sinai Health System.

When consumed in excess, this can result in jitters and anxious feelings, but it helps to eat before drinking coffee, Dieras added.

Why Coffee Makes You Rush to the Bathroom

Coffee may also affect your bowel movements in the morning, which may be exacerbated if you drink it on an empty stomach.The urge to go often happens in the morning, within a few hours of drinking coffee.

“If you have slower motility or constipation, it can help improve motility and speed things up,” said Rabia De Latour, MD, a gastroenterologist and assistant professor in the department of medicine at NYU Langone Health.

The laxative effect can sometimes lead to diarrhea if you don’t have constipation issues.

You may also have to pee more often. Caffeine signals the pituitary gland to reduce a hormone associated with water absorption in the kidneys, which leads to more urine output.

Why You Crash After a Coffee Buzz

The buzz from your morning coffee will likely fade sometime around lunch.

Caffeine boosts energy by blocking a neurotransmitter, called adenosine, from binding to receptors in the brain.

“Once caffeine begins to wear off, the accumulated free adenosine is finally able to bind to its receptors, sometimes triggering a sudden onset of fatigue,” said Stephani Johnson, DCN RD, an adjunct professor of clinical and preventive nutrition sciences at Rutgers University School of Health Professions.

Around this time, you may also notice a headache, as this is a side effect of caffeine withdrawal.You may also experience a low mood, difficulty concentrating, irritability, and not being able to think clearly.

How Late-Day Coffee Affects Your Sleep

Caffeine can stay in your system for 10 to 12 hours. If you drink coffee too late in the day, it can disrupt your sleep.

Johnson said a good rule of thumb is to avoid caffeine after 2 p.m. “Consuming caffeine too late in the day can lead to changes in sleep architecture, reducing deep, restorative sleep while increasing lighter, less restorative sleep.”

Not All Coffee Is Created the Same

Not all types of coffee affect your body the same way.

“Coffee varies widely, and I would caution any coffee drinker to know the caffeine content,” DeLatour said.

“Starbucks decaf has more caffeine than most people are aware of, and their regular coffee has more caffeine than certain energy drinks,” she added.

How much coffee you drink and how much caffeine is in your coffee can affect your body in different ways throughout the day.