Last updated: October 2026
Coffee on an empty stomach isn’t harmful for most people. But it can trigger heartburn in some, make you feel jittery or anxious, and lead to an energy crash. One study found coffee before breakfast raised blood sugar after a bad night’s sleep. If it bothers you, have it with or after food.
Below: what coffee does to your stomach, the jitters and anxiety, blood sugar, the best time for your first coffee, and who should be careful.
Your stomach
Coffee makes your stomach produce more acid and can relax the valve at the top of your stomach, which is why a review found it can promote acid reflux. But the same review found coffee wasn’t linked to general indigestion. If you get heartburn, an empty stomach can make it worse, so try having coffee with breakfast. See also gut health.
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View productJitters, anxiety and crashes
Caffeine works faster on an empty stomach, so you may feel more shaky, on edge or anxious, and then crash mid-morning. A mug of instant coffee has about 100mg of caffeine, according to the NHS. If you’re prone to anxiety, eating first and keeping to one or two cups helps. See does caffeine cause anxiety?, coffee crash and morning anxiety.
Blood sugar
In a University of Bath study, adults who drank strong black coffee before breakfast after a night of broken sleep had a higher blood sugar response to their breakfast. It’s one small study, but it suggests having breakfast first, especially after a poor night.
When to have your first coffee
| Tip | Why |
|---|---|
| With or after breakfast | Gentler on your stomach and steadier energy |
| Water first | You wake up slightly dehydrated |
| Daylight first | Morning light is a natural wake-up signal. See morning routine for energy |
| Last cup before about 2 to 3pm | Caffeine lingers for hours and can affect sleep. See how to sleep better |
Want a lower-caffeine option? See mushroom coffee.
Who should be careful
- Heartburn or reflux: have coffee with food, or cut down.
- Anxiety or palpitations: see anxiety symptoms.
- Pregnancy: the NHS advises no more than 200mg of caffeine a day.
- Poor sleep: keep caffeine to the morning.
For a calmer start to the day, many people take our Flow CBD Oil with breakfast, and our Magnesium Glycinate Sleep Complex is a caffeine-free evening drink. The FSA’s 10mg a day figure for CBD is precautionary advice rather than a legal limit, set while longer-term safety research continues. At Evopure we think it is a very cautious figure, and many adults use more. If you go above it, increase slowly, and check with your GP or pharmacist first if you take any medication.
Related guides
- Wondering if coffee counts? See how much water should I drink a day and what counts.
- How long caffeine stays in your system.
- If coffee doesn’t suit your stomach, see our guide to coffee alternatives.
- Is decaf coffee better for acid reflux?.
- If coffee gives you heartburn later in the day, see how to stop acid reflux at night.
- For breakfasts that pair well with your morning cup, see breakfast for energy.
- If coffee gives you heartburn, read how to deal with acid reflux.
- Taking iron in the morning? The NHS says to leave 2 hours before coffee; see iron tablets and coffee timing.
- If you add CBD to your morning cup, our guide to CBD coffee explains why it mixes best into milk.
- If an early coffee leaves you crashing later, see how to beat the afternoon crash.
Sources 4
- Boekema PJ et al (1999). Coffee and gastrointestinal function: facts and fiction. A review. Scandinavian Journal of Gastroenterology.
- Smith HA et al (2020). Glucose control upon waking is unaffected by hourly sleep fragmentation during the night, but is impaired by morning caffeinated coffee. British Journal of Nutrition.
- NHS. Heartburn and acid reflux.
- NHS. Caffeine content of drinks.
This guide is general information, not medical advice. Evopure makes Flow CBD Oil and the Magnesium Glycinate Sleep Complex. We don’t recommend our products during pregnancy or breastfeeding.
