This is a rough one if you rely on your morning cup of coffee or tea to get going each day. Soda and energy drinks are similarly dangerous if you already have issues with your kidneys. Studies show that long-term caffeine consumption can worsen chronic kidney disease and may increase the risk of kidney stones.
Caffeine is a mild diuretic, which affects the kidneys’ ability to absorb water. In reasonable amounts, this shouldn’t stop your kidneys from accessing enough water to do their job, but in excess it can be a problem.
Caffeine also stimulates blood flow and thereby increases blood pressure. Again, not a problem if you have normal blood pressure, but something to watch if your pressure is high.