Caffeine gets loads of us through that make-or-break first half of the day. But how much caffeine can you safely drink?

And exactly is caffeine? Well, it’s a natural stimulant that gives coffee, tea, many sodas, energy drinks, and candy their energizing zip. It works by stimulating the nervous system and making all systems really go.

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The Food and Drug Administration (FDA) maintains that an upper limit of 400 milligrams is the upper daily limit, above which it may cause side effects or health problems.

For context, one medium cup of brewed coffee (weighing 480 grams) provides 192 milligrams of caffeine.

This is a relief, as caffeine gives us the perfect energy kick to get us out the door and make us as coherent as possible during early morning meetings. And sometimes it takes more than one mug to deal with that spreadsheet.

However, too much caffeine can lead to scary jitters and have us counting sheep all night. Plus, if we become too dependent on caffeine, having to go without it can cause withdrawal effects like any illicit drug.

We explain how much caffeine you should drink in a day and what else to bear in mind.

The FDA has advised that 400 milligrams is the upper ceiling of daily caffeine consumption. However, this isn’t as simple or one-size-fits-all as it may first appear.

For example, the administration never specified what they classify as moderate or excess caffeine intake when it comes to women who are pregnant or of childbearing age and children themselves.

Health Canada went a little further in recommending limits for kids and women of childbearing age, as both of these groups may well face a greater health risk from caffeine:

  • Those who are of childbearing age should cap their caffeine intake at 300 milligrams per day.
  • Children aged 4 to 6 years should limit caffeine intake to 45 milligrams per day.
  • Children aged 7 to 9 years shouldn’t consume more than 62.5 milligrams per day.
  • Children aged 10 to 12 years should avoid consuming more than 85 milligrams per day.

If you’re in these groups and crave that morning coffee aroma, maybe have a think about going decaf instead.

Caffeine isn’t harmful in of itself, unless you either drink too much or have an insensitivity to it that triggers adverse reactions in your body. Which is, y’know, phew.

In fact, several studies have linked caffeine consumption to pretty nifty health benefits, including a reduced risk of liver cancer, links to a lower risk of death due to all causes, and a correlation between drinking 2 to 4 cups of coffee a day and a lower risk of suicide.

However, don’t go necking limitless cups of coffee as a elixir of life. Caffeine’s not without its side effects — especially if you drink too much or combine it with alcohol (looking at you, Jägerbombs).

We love a coffee smoothie — here’s our 7 favorite recipes.

The effects of excess caffeine

Everyone has a different tolerance to caffeine. Only you can really work out your limits. However, your body will show signs that you’ve had too much caffeine.

Research from 2015 suggests that the following are signs that you’ve reached your caffeine limit for the day:

  • feeling anxious
  • agitation and restlessness
  • difficulty drifting off to sleep
  • shakes and tremors

While they’re not the worst side effects in the world, they’re definitely uncomfortable and completely avoidable. You might, however, experience them a few times before you find a daily intake that feels comfortable for you.

The U.S. Department of Health and Human Services (HHS) comments that too few researchers have looked into the direct effects of caffeine for people with heart conditions or a genetic risk of one.

If you’ve got a diagnosed heart problem, you might want to exercise some caution when it comes to chugging coffee.

Caffeine withdrawal symptoms

Caffeine’s stimulating effects can lead to caffeine abuse disorder. And while it’s a more socially acceptable and safe stimulant than, say, mainlining speed at a work brunch, caffeine addiction is a real possibility.

If you find yourself feeling the following withdrawal symptoms and sensations when you go without your ritual morning tea or coffee, it could be that you really do have an addiction to caffeine:

Mixing caffeine with alcohol

This is an interesting effect, because the harmful aspects of combining caffeine with alcohol don’t really come from the caffeine.

Essentially, the extra energy from caffeine masks the woozy effects of the booze, meaning that you don’t feel as drunk. This might nudge people in the direction of drinking more, which increases the risk of alcohol-linked harm in the body.

Also, when did anything good happen after drinking Jägerbombs?

The Centers for Disease Control and Prevention (CDC) agree that research supports a link between people who combine alcohol with energy drinks and those who engage in binge-drinking behaviors.

Caffeine sensitivity

Some people feel the effects of caffeine more than others. This is known as having caffeine sensitivity. A lower daily intake may be sensible for people who experience this, given that they’re more prone to its adverse effects.

You’ll usually only know if you’re caffeine sensitive through experience — so if it usually gives you the wibbles or the effects feel like they last all day and night, maybe rein in your consumption.

A 2012 paper suggests that a particular gene, ADORA2A, is responsible for caffeine sensitivity.

Learn more about the power of the coffee nap here.

According to a 2017 review, caffeine stays in your blood for between 3 and 7 hours, and way longer for newborns (65 to 130 hours).

If you find yourself heading to your kitchen for another mug of mere minutes after your first, you’re loading your blood with caffeine when it’s very likely that the first caffeine delivery is still hanging about.

This is also why it’s important to limit caffeine intake during childhood. The liver and kidneys are simply less developed, so work slower when clearing caffeine from the body.

We investigated the nutrition labels of foods and drinks we already knew to be high in caffeine and were shocked by some of our findings.

Can you really have five Red Bulls in 1 day and still be under the limit!? The graphic below shows our findings.

In short, don’t worry — your daily dose of brown joy is still perfectly safe in its own right.

However, most people should cap their daily caffeine intake at 400 milligrams to avoid side effects. Those who are with child or hoping to be should limit intake to 300 milligrams per day, and children should consume far less.

If you consume absurd amounts of caffeine every day, you might feel super-crappy without it. Caffeine withdrawal is real, and it sucks. But caffeine also provides a whole bunch of benefits. It’s just about balance and moderation.

And limiting caffeine intake doesn’t only mean keeping an eye on the obvious culprits — coffee, tea, soda, and energy drinks. It’s in chocolate, too (we know, we know).

Researchers have a lot left to learn about the broader impact of consuming too much caffeine, so take it easy and find other ways to boost your energy throughout the day.