Coffee is something many of us rely on to kickstart the day or power through an afternoon slump. But sometimes, that trusty cup of coffee seems to stop working like it used to—and worse, it can start making you feel bad instead of good. Why does this happen?
First, your body can get used to caffeine. When you drink coffee regularly, your brain adjusts by reducing the number of caffeine receptors or changing how sensitive they are. This means over time, the same amount of coffee gives you less energy and alertness than before. You might find yourself needing more cups just to feel awake.
But drinking more coffee isn’t a harmless fix—it can backfire. Too much caffeine raises your cortisol levels, which is a stress hormone in your body. Elevated cortisol can increase blood pressure and heart rate and may even contribute to weight gain or diabetes if it stays high for too long. So that extra cup might actually be stressing you out without you realizing it.
Coffee also affects people differently depending on their health and genetics. Some people metabolize caffeine slowly; for them, even moderate amounts can cause anxiety, restlessness, or digestive problems like stomach upset or acid reflux.
Another issue comes from when and how you drink coffee. Having multiple cups in mid-morning when cortisol is naturally higher could push stress hormones up further—making your heart work harder and potentially causing jitters or nervousness.
Plus, if you’re taking certain medications, coffee might interfere with how those drugs work or increase side effects such as headaches or nausea.
Even decaffeinated coffee isn’t completely free from effects on the heart because other compounds in coffee besides caffeine influence cardiovascular function.
In short: Coffee stops working well when your body adapts to regular doses but then suffers from too much stimulation if you try to compensate by drinking more. It starts hurting when elevated stress hormones affect your heart and metabolism or when sensitivity causes unpleasant symptoms like anxiety and digestive trouble.
If you’ve noticed that morning brew no longer perks you up but instead leaves you feeling uneasy or wired-and-tired at once—that’s likely why: Your body’s balance with caffeine has shifted from helpful boost toward harmful strain.
