Listen, as a busy mom of three little boys who spends as many hours a week at sports practices as I do working , I know for a fact that coffee is not just a morning necessity.

That said, since we all know that sleep is vital to our wellbeing, and that coffee can disturb our sleep, there must be a cutoff time for enjoying a steaming cup, right?

Coffee blocks the effects of adenosine, which is a chemical that promotes sleep, as well as reducing melatonin levels.

Conversely, it can increase anxiety, and pretty much do anything else it can, as a stimulant, to keep us awake.

That said, there is research to show that coffee drinkers can also report feeling more tired throughout the day. This could be tied to the fact that people who had a bad night’s sleep and are already tired are reaching for a big mug, but research exists that shows the relationship between poor sleep and coffee is a bit of a chicken and egg situation.

They show that people who eschew coffee for even 24 hours get better quality and longer sleep.

Abhinav Singh is the medical director of the Indiana Sleep Center told the Sleep Foundation that every coffee drinker should stop and take stock once in a while.

“If you find yourself struggling to fall and stay asleep when tired, look at your entire caffeine intake and see how much is getting into your system. Start to reduce or eliminate as much as possible. There are hidden sources of caffeine that are present everywhere, including chocolate, workout drinks, body washes, and face creams.”

Still, if you only have one cup a day, but it’s too close to bedtime, it could still spell trouble.

That said, it comes down to genetics in most cases – which is to say, the answer of exactly how late is too late is different for everyone.

The “coffee gene,” CYP1A2, exists in duplicate for some people, which allows them to metabolize coffee faster than the rest of us.

If you don’t have two copies of the gene, registered dietician Anthony DiMarino says “it can take 2-10 hours for just half of caffeine’s effects to wear off. This ‘half-life,” as it’s known, varies from person to person.”

So if we figure most people are somewhere in the middle, it takes around six hours for half of the caffeine to wear off. If you want to start to wind down for bed by 10 pm, then, even a mid-afternoon cup might still be hanging around by then.

Sleep experts recommend having your last shot of caffeine around 2 or 3 in the afternoon if you have a typical workday schedule. Rashad Ramkissoon, a physician, says the reason is related to the importance of good sleep.

“Research on the exact timing caffeine’s impact on sleep is limited. But when it comes to getting quality sleep, it’s better to be safe than sorry.”

This is because even if caffeine can help keep you awake, it can’t counteract the other symptoms of sleep deprivation that can affect alertness and mental awareness, says research scientist Tracy Jill Doty.

“The performance advantage conferred by two daily 200 milligram doses of caffeine was lost after three nights of sleep restriction. That’s about four cups of coffee a day, which is the upper limit of what the FDA says is acceptable in a 24-hour period. These results are important, because caffeine is a stimulant widely used to counteract performance decline following periods of restricted sleep. The data from this study suggests that the same effective daily dose of caffeine is not sufficient to prevent performance decline over multiple days of restricted sleep.”

So try not to rely on it to be some kind of miracle, bring you back from the brink after a week with a newborn baby drug or anything.

In fact, if it’s after noon, you’d probably be better off taking a little nap instead.

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