For most of us it’s coffee or tea that kicks off the day. A quick flat white when heading to work, a tea at morning break, sometimes just a quick cold coffee at 3pm to get through the day.
Caffeine is used in the world as a stimulant more than any other drug, and for most healthy adults it’s considered safe in small amounts.
However, caffeine can easily get consumed in amounts that you were not aware of. Caffeine is present in foods that come in your way without your conscious effort, and the difference between a “little” and a “a lot”, is also dependent on your intake, timing, and the characteristics of your body. Here is a clear and comprehensive guide to caffeine.
The Daily Limit: How Much Is Too Much?
Australian guidance gives some simple benchmarks:
- Healthy adults: up to about 400 mg per day is considered safe for most people.
- Pregnant or breastfeeding women: the recommendation is to limit caffeine to about 200 mg per day.
- Children and teens under 18: much less. Health guidance suggests keeping intake low, and energy drinks aren’t a good idea for young people.
Heavy consumption of about 600 mg or more per day leads not necessarily to addiction or overdose, but to problems such as restlessness, anxiety, heartburn, nausea, etc. The effects will vary depending partly on the caffeine sensitivity level that you may be aware or unaware of.
All these are merely guidelines, and they are not magical numbers. Some individuals may feel jumpy after drinking coffee, while others are able to handle quite a bit of caffeine without a hitch. Should you develop a stomach or other problems as a result of consuming caffeine, chances are your safe limit of intake is lower than what is advised, but it should still be fine as it is an individual thing.
What’s in Your Cup?
Caffeine content varies a lot depending on the brand, brewing method and size. The numbers below, based on Australian health guidance, give a useful idea:
| Drink | Approximate caffeine |
| Espresso (50 mL) | around 145 mg* |
| Instant coffee (1 teaspoon) | around 80 mg |
| Energy drink (250 mL can) | around 80 mg |
| Large energy drink (500 mL can) | up to about 160 mg |
| Black tea (220 mL cup) | around 50 mg |
| Cola (375 mL can) | around 36 mg |
| Milk chocolate (50 g bar) | around 10 mg |
Cafe coffees vary a lot. Some sources list a single espresso shot as lower than this, and a large takeaway coffee can contain much more than a small cup. If you drink café coffee every day, assume your intake may be higher than you think.
A Day in Caffeine
Here’s how fast it adds up:
- Large coffee at 7am: about 150 to 200 mg
- Instant coffee at morning break: about 80 mg
- Cola with lunch: about 36 mg
- Energy drink at 3pm: about 80 mg
- Tea after dinner: about 50 mg
That’s roughly 400 to 450 mg, without anything unusual. If you’re feeling wired and can’t sleep, it may be worth adding up your own day.
Signs You’ve Had Too Much
Common signs include:
- Jitters, shakiness or restlessness
- A racing or pounding heart
- Feeling anxious or on edge
- Headaches
- Upset stomach or heartburn
- Needing the toilet more often
- Trouble falling or staying asleep
If you get chest pain, a very fast or irregular heartbeat, or feel faint, get medical help straight away.
When Should You Stop Having Caffeine?
Timing matters just as much as quantity. Caffeine has a half-life of around five hours on average. That means half of the caffeine from a 3pm coffee may still be in your system at 8pm. The effect varies a lot from person to person, and some people clear it more slowly.
A good rule of thumb is to stop caffeine at least six hours before bedtime. If you’re sensitive, or you struggle with sleep, eight hours may suit you better. So if you go to bed at 10:30pm, try to have your last caffeine by about 4:30pm, or earlier.
If you work night shifts, use the same idea based on when you plan to sleep, not on the clock. Have your caffeine early in your shift, and stop four to six hours before you go to bed after work. See our guides on sleeping after a night shift and what to eat on night shift.
Who Should Be Extra Careful?
Some people need to take more care:
- Pregnant and breastfeeding women should stick to the lower limit of about 200 mg a day.
- Teenagers and children. Energy drinks in particular are best avoided.
- People with anxiety or panic attacks. Caffeine can make symptoms worse.
- People with heart rhythm problems or high blood pressure. Ask your doctor what’s safe for you.
- People with reflux, ulcers or stomach problems, since caffeine can aggravate them.
- People with insomnia, who may do better with less caffeine, earlier in the day.
- People on certain medicines. Some medicines change how quickly your body clears caffeine, and some can add to its effects. Ask your pharmacist or GP if you’re unsure.
Hidden Sources of Caffeine
It’s not just coffee and tea. Caffeine also turns up in:
- Energy drinks and energy shots (a small 60 mL shot can have around 150 mg)
- Pre-workout supplements
- Some headache and cold-and-flu tablets
- Chocolate and cocoa
- Some sports gels and bars
A quick note on safety: pure caffeine powders are banned from retail sale in Australia, because a single teaspoon can contain as much caffeine as dozens of cups of coffee and can be dangerous. If you ever come across a product like this, avoid it.
How to Cut Back Without the Headache
If you’ve decided to drink less, going cold turkey can bring headaches, tiredness and a bad mood for a few days. A gentler approach works better:
- Work out your current intake over a few normal days.
- Reduce gradually. Cut back by about a quarter every few days, or swap one drink a day for half-strength or decaf.
- Replace the ritual. Try herbal tea, hot water with lemon, or sparkling water.
- Drink water. Being well hydrated helps with headaches and tiredness.
- Get more sleep. It’s the best fix for the tiredness that made you reach for caffeine in the first place.
What Caffeine Can’t Do
Caffeine hides tiredness, but it doesn’t remove the need for sleep. If you rely on several coffees a day just to function, the real issue may be your sleep, not your caffeine. Poor sleep, sleep apnoea, shift work and other health problems can all cause ongoing fatigue that no amount of coffee will fix.
When to See Your GP
Talk to your doctor if:
- You feel exhausted even though you’re having plenty of caffeine
- You get palpitations, chest pain or panic-like symptoms
- You can’t cut down without feeling unwell
- You’re pregnant, planning a pregnancy or breastfeeding and unsure about your limits
- You take regular medicines and want to check for interactions
- You nod off during the day or while driving
Our guide “Always Tired? How to Tell If It’s Excessive Daytime Sleepiness” can help you work out what to ask.
The Bottom Line
For most healthy adults, up to about 400 mg of caffeine a day is fine, which is roughly the same as a few regular coffees. Keep a rough tally, remember that energy drinks and café coffees can add up quickly, and stop at least six hours before bed to protect your sleep. If you’re pregnant, sensitive to caffeine or relying on it just to get through the day, it’s worth cutting back and finding out what’s behind the tiredness.
This article is general information only and isn’t medical advice. If you have concerns about your caffeine intake or health, speak with your GP or pharmacist.