Coffee and Cortisol: What the Studies Actually Show
Coffee is often blamed for raising cortisol, especially first thing in the morning or on an empty stomach. Some of that is backed by research. Some of it isn't.
Here's what the studies show about caffeine and cortisol, and where the popular advice goes further than the evidence.
This article is for general information and isn't medical advice.
Does caffeine raise cortisol?
Yes, at least in people who aren't used to it. In a controlled trial, Lovallo and colleagues had healthy young adults avoid caffeine for five days and then take caffeine on a test day. Their cortisol rose clearly across the day (Lovallo et al., 2005).
Do regular coffee drinkers still get the effect?
Less so. In the same trial, the same people also spent five days taking caffeine every day at moderate or high intake. After that, their first caffeine dose of the test morning no longer raised cortisol. But cortisol did rise again after a second dose in the early afternoon. The authors concluded that the cortisol response is reduced, but not eliminated, in daily caffeine users (Lovallo et al., 2005).
In plain terms: if you drink coffee every day, your morning cup probably does less to your cortisol than the internet suggests. Extra cups later in the day may still have an effect.
Coffee on an empty stomach and cortisol
This is one of the most repeated claims, and we couldn't find a study that tested it directly. The study usually linked to it measured something else. In a 2020 crossover trial of 29 adults, Smith and colleagues found that strong black coffee after a night of broken sleep raised the blood sugar response to a sugary breakfast drink (Smith et al., 2020). It reported blood sugar and insulin after poor sleep, not cortisol.
So if coffee on an empty stomach upsets your stomach or leaves you jittery, it's reasonable to have it with or after food. Just know that the "empty stomach cortisol spike" isn't something the research has shown.
What the research says, at a glance
| Claim | What the research shows | How strong |
|---|---|---|
| Caffeine raises cortisol | Clear rise after caffeine in people who'd been off it for five days (Lovallo et al., 2005) | Strong, in controlled conditions |
| Daily coffee drinkers adapt | Morning response disappeared with daily use; an afternoon rise remained (same study) | Moderate; one trial |
| Coffee on an empty stomach spikes cortisol | No direct test found. A related trial measured blood sugar after poor sleep, not cortisol (Smith et al., 2020) | Not shown |
| Late caffeine disrupts sleep | Caffeine six hours before bed cut measured sleep by more than an hour in 12 people, who didn't seem to notice (Drake et al., 2013) | Moderate (small study) |
Does it matter for feeling wired but tired?
The clearest link isn't cortisol. It's sleep. In the Drake trial, caffeine taken six hours before bed still cut sleep by more than an hour, and participants didn't seem to notice. If you're exhausted but can't switch off at night, when you have your last coffee is likely to matter more than whether your morning cup nudges your cortisol. We cover that pattern in wired but tired, and night waking in waking up at 3am.
Cortisol is naturally highest around the time you wake, as we explain in why cortisol is high in the morning. Some people suggest waiting before the first coffee for that reason. We didn't find a trial testing whether that makes a difference, so think of it as a personal preference, not a rule.
Practical takeaways
- Watch the timing of your last cup. This has the clearest research behind it.
- If coffee on an empty stomach bothers you, pair it with breakfast. That's comfort, not cortisol control.
- Notice how you feel. People respond to caffeine differently, and regular drinkers adapt.
If you'd like a simple structure for meals and drinks across the day, the balanced-plate section of The Cortisol Paradox 21-day routine pairs breakfast with protein, slow carbs and healthy fats. See the balanced-plate part of the 21-day routine.
When to see a doctor
Talk to a doctor if caffeine gives you a racing or irregular heartbeat, chest pain, bad heartburn or panic. Also check with your doctor about caffeine if you're pregnant, have a heart condition or high blood pressure, or take medicines that may interact with it.
FAQ
Does coffee raise cortisol?
Caffeine raises cortisol in people who aren't used to it. In daily drinkers, the effect is smaller, and the first morning cup may not raise it at all.
Is caffeine or coffee the cause?
The Lovallo trial used caffeine capsules, so the effect is from caffeine. We didn't find good evidence on decaf or other parts of coffee and cortisol.
Should I drink coffee before or after breakfast?
Research hasn't shown a cortisol reason to choose. One trial found coffee after a night of broken sleep raised the blood sugar response to a sugary drink. The trial didn't test coffee with food, so take it as a reason for caution after a bad night, not a rule.
The short version
Caffeine raises cortisol, but daily coffee drinkers adapt to much of the effect. The "empty stomach cortisol spike" hasn't been shown in research. For most people who feel wired but tired, the timing of the last cup matters more than the first.
Last reviewed: October 29, 2026
This article is for general information and isn't medical advice. If you're worried about your health, talk to a doctor.