If you’re reading this, odds are you had caffeine this morning (or maybe you’re consuming it right now). The most widely used psychoactive stimulant in the world, caffeine is present in everything from coffee and tea to soda and chocolate.

In moderate doses, it’s known to increase alertness, improve focus, and reduce fatigue. But if you’ve ever felt that jittery feeling that comes from downing one too many shots of espresso, you may not be surprised to learn that it’s possible to overdo it.

How does it work?

What exactly is it about coffee that helps us feel awake? “Coffee is known as an ‘adenosine antagonist,’ meaning it counteracts the affects of the chemical adenosine by blocking its receptor sites in the brain,” says Dr. Josh Axe, DNM, DC, CNS. Our bodies naturally produce adenosine throughout the day so we can fall asleep easily at night. When we ingest caffeine, it interferes with this process and helps us feel more energized regardless of the time of day.

It’s important to note that many caffeinated drinks, such as coffee and tea, have health benefits that aren’t directly related to their caffeine content. The chemical compounds in coffee are thought to protect against chronic disease, and the flavonoids (a type of plant chemical) in tea have known anti-inflammatory properties. These effects are present even in decaffeinated versions of your favorite beverages.

So how much is too much?

It depends on who you ask. Even though caffeine might make you feel superhuman, a fair number of studies out there warn about its negative effects. In large doses, caffeine can worsen anxiety and make it difficult to sleep, and it can sometimes actually make concentration more difficult. But the exact amount it takes for these symptoms to kick in might be different for each person.

It’s hard to say how much caffeine is too much because the substance can have vastly different effects depending on the person consuming it. Veteran coffee drinkers might laugh in the face of danger (cue “I drink five cups a day and I’m doing fine!”) but they may have a scientific reason to do so. People naturally build up a tolerance to the effects of caffeine, meaning they need more and more to reach the same buzz.

Genetics also come into play—caffeine is metabolized at different rates depending on your variation of the CYP1A2 gene. Some people are identified as “slow metabolizers,” and they may be more likely to feel the effects of caffeine at lower doses. So if your office buddy always downs three cups of cold brew before 10 a.m. while it only takes two gulps to get you going, you might just be processing it differently.

“Most research suggests that adults can consume about 3-4 cups/day safely without any health risks,” says Dr. Axe. This is considered a moderate intake of coffee, and it should be fine as long as it’s not interfering with your ability to focus or sleep. For some people, more is okay, but it’s imporant to be mindful of how it’s affecting your body.

What happens if I overdo it?

In super high doses, caffeine can have some scary consequences. In April of this year, the FDA issued a warning against highly concentrated caffeine supplements, which contain as much as 3,000 mg per teaspoon. That’s equivalent to the amount of caffeine in 30 cups of coffee, so this stuff is no joke.

In another report, the FDA cautions that toxic effects, like heart arrhythmia and seizures, can happen at 1,200 mg (around 12 cups of coffee), and risk of death starts at around 10,000 mg (100 cups of coffee)—way more than anyone could drink in a single day.

In other words, it’s highly unlikely you’ll die from drinking coffee. But you might begin to feel negative effects after drinking only a few cups per day. Caffeine definitely has addictive properties (ever experience headaches when you skip your morning bev?), and it’s hard to quit once you’ve made it a regular habit. Caffeine withdrawal is actually recognized as a disorder by the American Psychiatric Association, and its effects can kick in within 12-24 hours after a person stops drinking caffeine. Symptoms include decreased energy, irritability, and foggy-headedness (sadly, sounds like the same feelings we have in the morning before coffee).

Often, someone may not notice how much caffeine is affecting them until they take a step back and start drinking less. If you’re hoping to reduce your consumption without feeling like crap in the process, a gradual approach can prevent you from noticing symptoms. Try drinking just a little less each day until you’re down to an amount that feels reasonable for you.

The takeaway

Ultimately, it comes down to how caffeine makes you feel. Do you start to get jittery and anxious by that second or third cup? This might mean you need to cut back on the habit. If four cups of coffee is the magic number to help you power through the day, then by all means, you do you—just make sure you aren’t growing so dependent that it affects your sleep or makes you feel like you can’t function without it. Caffeine can be a tool to help you stay motivated, but nothing beats the all-natural energy boost that comes from working out, eating well, and resting when your body needs it.