The kidneys filter your entire blood supply many times a day, and they are sensitive to things that stress blood vessels, such as high blood pressure and diabetes. Coffee raises blood pressure briefly and makes many people urinate more, so it is not surprising that people wonder whether a daily habit wears the kidneys down. The research on this question is interesting because it contains a genuine disagreement between two types of evidence, and understanding why they disagree is more useful than picking a side.
How kidney health is measured
Researchers usually track kidney health with two measurements. The first is estimated glomerular filtration rate, or eGFR, calculated from a blood test, which estimates how much blood the kidneys filter each minute. Chronic kidney disease is typically defined as an eGFR below 60 ml per minute sustained over time. The second is albuminuria, the presence of the protein albumin in urine, which is an early sign that the kidneys' filters are leaking. Kidney failure, or end-stage kidney disease, is the point at which dialysis or a transplant becomes necessary. Kidney stones are a separate problem, hard mineral deposits that form in the urine, but they are often studied alongside kidney disease because diet and fluid intake affect both.
A 24-year study of 14,000 adults
The longest single study is the analysis of the Atherosclerosis Risk in Communities study by Hu and colleagues in the American Journal of Kidney Diseases[1]. They followed 14,209 adults aged 45 to 64, assessing coffee intake with food questionnaires at two visits, and counted 3,845 new cases of chronic kidney disease over a median of 24 years.
After adjusting for demographic, clinical and dietary factors, every category of coffee drinking was associated with lower risk compared with never drinking coffee. The hazard ratios were 0.90 for less than a cup a day, 0.90 for one to two cups, 0.87 for two to three cups, and 0.84 for three or more cups a day. Treated as a continuous measure, each additional daily cup was associated with a 3% lower risk. The authors listed self-reported intake and the observational design as the main limitations, and concluded cautiously that coffee drinkers may not be at increased risk of kidney disease.
What the pooled analyses found
Several meta-analyses have combined these cohorts. The largest, by Kanbay and colleagues in the Journal of Renal Nutrition[2], included 12 studies with 505,841 participants. Coffee drinking was associated with a lower risk of developing chronic kidney disease, with a relative risk of 0.86, and the reduction was larger at two or more cups a day than at one cup or less. Coffee drinkers also had a lower risk of end-stage kidney disease, a hazard ratio of 0.82, a lower risk of albuminuria, an odds ratio of 0.81, and a lower risk of kidney-related death, a hazard ratio of 0.72.
A smaller meta-analysis restricted to cohort studies by Srithongkul and Ungprasert[3] pooled 4 studies with 25,849 people and found a similar result, a pooled risk ratio of 0.87 for incident kidney disease among coffee drinkers compared with non-drinkers. An earlier analysis by Wijarnpreecha and colleagues[4], working with only 4 studies and 14,898 people, was less conclusive: its pooled relative risk of 0.71 was not statistically significant, and when split by sex the estimates were 1.10 for men and 0.81 for women, neither significant. That earlier result is a reminder of how much these conclusions depended on the size of the evidence base at the time.
The genetic analysis that found nothing
Here is where the story gets more interesting. Observational studies can be fooled by confounding: coffee drinkers may be healthier, wealthier or less likely to have diabetes in ways that the adjustment does not fully capture. One way researchers try to get around this is Mendelian randomisation, which uses gene variants that make people drink a bit more or less coffee. Because genes are assigned at conception, largely independently of lifestyle, they act like a natural randomisation.
Mazidi and colleagues[5] combined three approaches in a 2022 study. In US national survey data on 18,436 people, the share with kidney disease fell across quartiles of caffeine intake, from 16.6% in the lowest to 11.0% in the highest, but after full adjustment there was no significant difference in the likelihood of kidney disease and no significant change in eGFR or urine albumin. Their Mendelian randomisation analysis, using genetic data on coffee intake from 91,462 people and kidney function from 133,413, found no effect of coffee on kidney disease or eGFR, in people with or without diabetes. Their own meta-analysis of 6 studies gave an odds ratio of 0.85 that was not statistically significant.
Reconciling the two readings
The observational studies say coffee drinkers get kidney disease somewhat less often. The genetic analysis says coffee itself probably does not change kidney function. These are less contradictory than they look. The most natural reconciliation is that the lower risk seen among coffee drinkers is at least partly explained by other differences between drinkers and non-drinkers, while coffee's own effect on the kidneys is close to neutral.
Mendelian randomisation has its own limits, including the assumption that the genes involved affect kidneys only through coffee intake, so it does not settle the matter. What both approaches agree on is the part that answers the question most people are asking. Neither found that coffee harms the kidneys of people without kidney disease. The disagreement is only about whether the effect is neutral or mildly favourable.
Sudden kidney injury, not just slow decline
Chronic kidney disease develops over years. Acute kidney injury is different: a sudden drop in kidney function, often during a hospital stay, a severe infection, dehydration or a reaction to medication. Because coffee is sometimes suspected of stressing the kidneys, it is worth knowing whether coffee drinkers are more prone to these sudden episodes. The same long-running cohort answered that too. Tommerdahl and colleagues, writing in Kidney International Reports[6], used the Atherosclerosis Risk in Communities data on 14,207 adults and counted 1,694 hospitalisations with acute kidney injury over a median of 24 years.
Compared with people who never drank coffee, the hazard ratios were 0.92 for less than a cup a day, 1.08 for one cup, 0.83 for two to three cups, and 0.83 for more than three cups. The individual categories below two cups were not statistically clear, but the trend across categories was significant and remained so after adjusting for age, sex, education, calorie intake, exercise, smoking, alcohol, diet quality, blood pressure, diabetes, blood pressure medication, kidney function and body weight. Coffee was assessed only once, and this is a single cohort, so it is a modest piece of evidence. It points in the same direction as the chronic disease studies rather than against them.
Looking inside the blood for an explanation
If coffee drinkers really do have somewhat healthier kidneys, the obvious question is what in the drink might be responsible. A 2021 study by He and colleagues in the Clinical Journal of the American Society of Nephrology[7] took an unusual approach. Instead of asking about cups, they measured 372 metabolites, small molecules circulating in the blood, in 3,811 participants of the same American cohort, and checked their results in 1,043 people from a second study, the Bogalusa Heart Study.
They found 41 metabolites associated with coffee drinking, of which 20 were confirmed in the second cohort. Three of those 20 were linked to later chronic kidney disease. One, glycochenodeoxycholate, a bile acid involved in fat metabolism, was associated with better kidney outcomes and may be part of any benefit. The other two, O-methylcatechol sulfate and 3-methyl catechol sulfate, are compounds from the breakdown of benzoates, and the authors flagged them as possible markers of harmful aspects of coffee for the kidneys.
That finding is worth sitting with, because it complicates the simple story. Coffee is a mixture of hundreds of compounds, and there is no reason every one of them should act in the same direction. A plausible reading is that coffee contains both potentially helpful and potentially unhelpful ingredients for the kidneys, with the observational studies capturing the net result in populations that mostly drink it in moderation. These metabolite links are associations too, and they generate hypotheses rather than settle them.
Coffee and kidney stones
Kidney stones are a different condition with their own evidence. The concern is reasonable: caffeine can increase the amount of calcium lost in urine, and most stones contain calcium. Yet a study of three large cohorts by Ferraro and colleagues in the American Journal of Clinical Nutrition[8] found the reverse association. Across 217,883 participants followed for a median of more than 8 years, with 4,982 new stones, people in the highest fifth of caffeine intake had a 26% lower risk of stones in the men's cohort, 29% lower in the older women's cohort, and 31% lower in the younger women's cohort, after adjustment for fluid intake, weight and other factors.
Among 6,033 participants who collected 24-hour urine samples, caffeine intake was associated with higher urine volume, higher calcium and potassium, and lower oxalate and lower supersaturation for calcium oxalate and uric acid. In other words, the extra urine appears to dilute the stone-forming ingredients more than the extra calcium concentrates them. An earlier analysis of the same cohorts by Ferraro and colleagues[9] compared many drinks and found a 26% lower stone risk for caffeinated coffee and a 16% lower risk for decaf, while sugar-sweetened cola was linked to a 23% higher risk and sugar-sweetened non-cola drinks to a 33% higher risk.
Why the extra trips to the bathroom are not kidney damage
Part of the worry behind this search query is simple experience: coffee makes many people urinate more, and it is natural to read that as the kidneys being pushed harder. Producing more urine is not the same thing as damage, though. The kidneys adjust urine volume constantly in response to how much fluid you drink, and a mild increase in output is the organ doing its normal job rather than straining. None of the studies above found signs of harm, such as falling filtration rates or rising albuminuria, in coffee drinkers.
The stone research even turns the extra urine into a possible advantage. Higher urine volume was one of the changes Ferraro and colleagues[8] measured alongside caffeine intake, and more dilute urine is less likely to form crystals. Whether coffee actually dehydrates you over a day is a separate question with its own trial evidence, covered in the article linked at the end of this page.
The limits of all of this
These are observational studies, with self-reported coffee intake, mostly in American and European populations. They describe associations in people who did not have kidney disease at the start. The Mendelian randomisation result shows how easily such associations can reflect other differences between groups, which is why the evidence rating on this article is contested rather than moderate.
Most importantly, none of this is about people who already have chronic kidney disease or kidney failure. For them, the questions are different: how much fluid is allowed, how much potassium the diet can contain, since coffee contributes some, and how caffeine interacts with blood pressure control and medication. Those are individual decisions for a nephrologist or dietitian, and population averages from healthy people should not override them.
The practical takeaway
For people with healthy kidneys, the answer to the search query is no: the large studies do not show coffee damaging the kidneys, and they consistently link it with a lower risk of kidney stones. Whether coffee actively protects the kidneys is uncertain, because genetic evidence suggests the apparent benefit may come from other differences between coffee drinkers and non-drinkers. What you add to the cup matters too. The stone studies found sugar-sweetened drinks going the wrong way, so a heavily sweetened coffee drink is not the same exposure as black coffee.
Because high blood pressure and gout are both closely tied to kidney health, our article on coffee and blood pressure and the article on uric acid and gout are useful companions, and the article on whether coffee dehydrates you covers the urine question in more detail. Nothing here is medical advice.