90-Minute Rule: Sleep Experts Reveal the Best Time for Your First Coffee.

When to Drink Coffee After Waking Up

According to TSN.ua: According to Dr. Michael Breus, a leading sleep specialist from the United States, waiting 90 minutes after waking up before drinking coffee can significantly boost caffeine’s effectiveness. He explains that the body can lose nearly a liter of fluid overnight just through breathing. This substantial water loss can affect how you feel upon waking.

To counteract this, Dr. Breus recommends drinking three to four glasses of water within the first hour and a half of the day. He also notes that levels of cortisol and adrenaline are already elevated after sleep, which may reduce the body’s need for caffeine.

“Caffeine acts as a diuretic, so it can actually increase fluid loss,” Dr. Breus emphasizes.

Research and Scientific Findings

A 2025 study from the University of Arizona supports the idea that coffee should be delayed by about two hours after waking. Adenosine, the chemical responsible for drowsiness, decreases during sleep, and if its levels haven’t fully reset, caffeine’s stimulating effect may be weaker.

“If you add caffeine at that point, its stimulating effect will be less pronounced,” Breus explains.

Researchers also highlight several benefits of postponing your morning coffee:

• The stimulating effects of coffee can last longer.
• It helps the body retain fluids.
• It boosts caffeine’s efficiency for active individuals.

By following these expert recommendations, you can optimize your coffee intake and improve your overall state after sleep. These tips are especially valuable for those who rely on caffeine to boost energy and focus in the morning. Understanding how your body works during sleep and in the first hours after waking can lead to better daily well-being.