For someone whose blood pressure is already poorly controlled, drinking large amounts of strong coffee may not be a good choice. Persistent high blood pressure can damage the small blood vessels in the kidneys, gradually reducing their ability to filter blood.
This is one reason people with hypertension should pay attention to their caffeine intake and discuss any concerns with their healthcare professional.
The National Kidney Foundation explains that caffeine can cause a temporary increase in blood pressure. It also notes that people who struggle to control their blood pressure may need to limit their coffee consumption.
National Kidney Foundation
Does coffee dehydrate the body?
Another common belief is that coffee causes dehydration and therefore damages the kidneys.
Caffeine can have a mild diuretic effect, meaning it may increase urine production. However, the fluid in a normal cup of coffee still contributes to daily fluid intake. For most habitual coffee drinkers, moderate consumption does not automatically cause dehydration.
The situation may be different for people who have been instructed to restrict fluids because of advanced kidney disease, heart failure, or another medical condition. In those cases, coffee must be counted as part of the person's total fluid allowance.
The National Kidney Foundation specifically advises people on fluid restrictions to include coffee in their daily fluid intake.
National Kidney Foundation
What about potassium?
Coffee naturally contains potassium. For many healthy adults, the amount in a normal serving is not a major concern.
However, some people with advanced kidney disease have difficulty removing excess potassium from the blood. High potassium levels, known as hyperkalemia, can affect normal muscle and heart function and may become dangerous.
The National Kidney Foundation notes that an eight-ounce cup of black coffee contains approximately 116 milligrams of potassium. It also explains that drinking three to four cups daily may contribute a higher potassium intake, particularly when milk or creamers are added.
National Kidney Foundation
This does not mean every kidney patient must avoid coffee. Potassium recommendations depend on blood test results, kidney function, medications, and the overall diet.
Can coffee protect the kidneys?
Some research has found associations between coffee consumption and a lower risk of CKD. The 2025 Scientific Reports study involving nearly 50,000 participants reported such an association, but its observational design means that it cannot prove cause and effect.
People who drink coffee may differ from non-drinkers in many other ways, including diet, activity, smoking habits, income, and existing health conditions. Researchers try to account for these factors, but observational studies cannot eliminate every possible source of bias.
The safest conclusion is that moderate coffee consumption appears compatible with kidney health for many people. It should not be promoted as a treatment for kidney disease, and it should not be blamed as a universal cause of kidney failure.
An illustrative photograph of instant coffee granules. Instant coffee is not automatically harmful to the kidneys.
The amount consumed, the type of drink, the added ingredients, and the person's medical condition all help determine whether a coffee habit is appropriate.
Chapter 3: Which Type of Coffee Should People Be Careful About?
The headline in the image warns against buying a particular type of coffee, but it does not name the product. That missing detail is important because different coffee drinks can have very different nutritional compositions.
Plain black coffee, instant coffee, sweetened three-in-one coffee, bottled coffee drinks, and large cafΓ© lattes are not interchangeable. They may contain different amounts of caffeine, sugar, milk ingredients, sodium, potassium, and phosphorus.
For people with kidney disease, some of these additional ingredients may be more important than the coffee itself.
1. Sweetened instant coffee mixes
Three-in-one coffee products commonly combine instant coffee, sugar, and creamer or milk powder. They are convenient, but their nutritional content varies considerably between brands.
A person who drinks several packets each day may consume a substantial amount of added sugar and calories without realizing it. Frequent consumption of sugar-sweetened drinks can make weight and blood glucose management more difficult.
This matters because diabetes is one of the leading risk factors for chronic kidney disease. Persistently elevated blood glucose can damage the small blood vessels that help the kidneys filter waste.
However, it is important not to exaggerate the connection. Drinking one packet of instant coffee does not automatically cause diabetes or kidney failure. The concern is the overall dietary pattern, particularly when high-sugar drinks are consumed frequently alongside other sources of excess calories.
2. Coffee creamers containing phosphate additives
One of the more important considerations for people with advanced kidney disease is phosphorus.
Phosphorus is a mineral needed for healthy bones and several normal body functions. Healthy kidneys help regulate the amount of phosphorus in the blood. When kidney function declines, phosphorus may accumulate, especially in people with advanced disease.