Is your daily caffeine hit ruining your sleep?

Updated June 2024 | 5 min read 
Expert contributor Dr Crystal Yates, research associate, University of South Australia 
Words by Karen Burge 

We’re sorry to break the news, but your daily caffeine hit could be ruining your sleep. Here’s how that extra cup can cause chaos at night.  

If you find it hard to fall asleep at night, and need a caffeine hit first thing in the morning to get moving, your reliance on caffeine could be covering up a negative sleep cycle, say experts at the Sleep Health Foundation. This could include waking up often through the night or finding it hard to get to sleep. 

How caffeine gives you a buzz

"Caffeine is a central nervous system stimulant that increases alertness and reduces sleepiness," making getting to sleep difficult, explains Dr Crystal Yates from the University of South Australia, who has conducted research in the area.

"This is because caffeine blocks adenosine activity (which promotes sleep), in turn increasing central nervous system activity and promoting wakefulness."

After consumption, levels of caffeine in your bloodstream peak within 30 to 70 minutes, but the bounce it gives you can last from three to seven hours. Plus, the caffeine can take up to 24 hours to fully leave your body.

Because of this, the Sleep Health Foundation recommends that it may be wise to avoid that last cup of coffee or tea, or other caffeinated foods and drinks, at least three to seven hours before bedtime – or even stop at lunchtime if you’re having sleeping problems. This gives your body more time to process it, which may help you get more shut eye. Then you have a better chance of waking up feeling more refreshed and be less dependent on caffeine.

Counting your caffeine load

If you’re a caffeine lover and have trouble sleeping, you might want to become more aware of the caffeine content you consume daily.

Caffeine is found in:

• foods like chocolate and energy bars
• drinks like tea, coffee and soft drinks (colas and energy drinks)
• some medications, like No-Doz.

Here’s how much caffeine content is in common foods and drinks, according to Food Standards Australia and New Zealand:

• Espresso: 145mg/50ml cup
• Energy drinks: 80mg/250ml can
• Instant coffee (1 tsp/cup): 80mg/250ml cup
• Black tea: 50mg/250ml cup
• Cola: 48.75mg/375ml can
• Milk chocolate: 10mg/50g bar

The exact amount in each will vary between products and brands, adds Dr Yates.

What’s the recommended daily caffeine limit?

According to the Sleep Health Foundation, up to 200mg of caffeine in a single dose, and a daily intake of less than 400mg doesn’t seem to have any negative effects in healthy adults. This is around five cups of regular strength black tea or two cups of brewed coffee per day.

When taken in low to moderate doses, caffeine can have a positive effect on the body, including promoting alertness and better cognitive performance, like concentration and problem solving.

But in higher doses, caffeine can cause:

• restlessness
• dehydration
• trembling hands
• sleep disruption
• headaches
• anxiety and irritability
• a rapid heartbeat
• a rise in body temperature.

If you’re pregnant, it's recommended you limit your caffeine intake at 200mg per day or less, or avoid it altogether.

For children under 12, small doses of caffeine in chocolate and chocolate-based drinks may be okay as a treat, but it's recommended to limit their intake of caffeine and avoid energy drinks.

Teens should also limit caffeine intake, as they could be more susceptible than adults to caffeine-related symptoms.

If you think that extra afternoon coffee or energy drink might be interfering with your sleep, a slow and steady cutback is the best approach to avoid withdrawal symptoms like headaches and fatigue.

Want to sleep better?

Thanks to our partnership with Sleepfit Solutions, eligible HCF members^* can get a free 12-month subscription to the Sleepfit app, which is designed to improve sleep and overall wellbeing.