Can drinking tea cause kidney stones? Not that exaggerated
2026-07-01
Can drinking tea cause kidney stones? The truth behind the myth
China’s tea culture has a long history, and tea drinking has long become an integral part of daily life for people across the country, serving as an important medium for self-cultivation and social interaction. With the rise in health awareness, the claim “drinking tea can cause kidney stones” has spread in public discourse, raising concerns among many tea enthusiasts: Is there really a link between tea drinking and kidney stones?
Why do stones form in the kidneys?
To clarify the relationship between tea and stones, we first need to understand how kidney stones form. Kidney stones are essentially crystals that gradually aggregate and grow when certain solutes in urine (such as oxalate, calcium, uric acid, etc.) exceed their solubility. Among them, calcium oxalate stones are the most common, accounting for over 80% of urinary tract stones. Since tea contains oxalate, the concern that “tea drinking causes stones” largely stems from this.
Oxalate content determines the risk
When discussing the link between tea and kidney stones, a key premise is that dose determines risk. Different types of tea vary in oxalate content in their brewed liquid: herbal teas have the lowest oxalate levels. Among tea-based beverages, some tea bags or loose-leaf teas may show higher oxalate content under specific brewing conditions. Even within the same tea category (e.g., green tea), differences in origin, quality, and processing methods can cause significant fluctuations in oxalate concentration in the brewed liquid—studies report a range as wide as 17 times (8.3–139.8 mg/L).
Brewing time and “concentration” matter equally
The longer and more concentrated the tea is brewed, the more soluble components (including oxalate) enter the liquid. Research shows that for the same black tea bag, oxalate content is about 10.8 mg/250mL after 1 minute of steeping, but rises to nearly double (20.8 mg/250mL) after 5 minutes. In other words, “strong tea” or “over-steeped tea” is not the same as “light tea,” and risk assessment cannot be generalized.
Total daily urine volume is equally critical
What’s important to note is that the risk of “strong tea-related issues” depends not only on the oxalate content in a single cup of tea, but also on whether total daily urine volume truly increases. Tea drinking increases fluid intake, and tea itself has a diuretic effect; increased urine volume reduces the precipitation of crystals in urine. For kidney stone patients, a 24-hour urine volume exceeding 2.5L is widely recognized as a key point for preventing recurrence.
However, if tea completely replaces plain water, or if fluid intake is insufficient due to sweating during exercise, leading to suboptimal 24-hour urine volume, the dilution benefit of tea drinking cannot be realized. Instead, urine remains concentrated, increasing the concentration of oxalate, calcium, and other substances, making crystal precipitation more likely. Long-term exposure to such conditions does increase concerns about stone formation or recurrence.
Gastrointestinal absorption affects stone risk
Additionally, gastrointestinal absorption of oxalate influences risk. Generally, dietary calcium in the gut can bind with oxalate, reducing oxalate absorption and lowering urinary oxalate levels—this is why “consuming moderate amounts of calcium-rich foods with meals” may help reduce oxalate load in some cases. Conversely, drinking strong tea on an empty stomach not only irritates the gastrointestinal tract and affects comfort, but may also increase the chance of oxalate absorption in individuals with varying metabolic characteristics.
Three key details for healthy tea drinking
Overall, existing research supports the conclusion that for the general population, moderate tea drinking typically does not increase kidney stone risk and may even be associated with a lower risk of stone formation. Therefore, there’s no need to give up tea drinking out of fear of stones.
Tea is not the “culprit” of kidney stones; rather, improper tea drinking habits may act as a “pusher” in stone formation. When drinking tea, focus on three points:
Prioritize light tea and avoid over-steeping;
Adhere to “tea as a supplement, plain water as the main source”;
Avoid drinking strong tea on an empty stomach.
Beyond tea drinking habits, individual constitution also matters. If you already have metabolic abnormalities such as hyperoxaluria or hypercalciuria, or a history of stones with high recurrence risk, excessive tea drinking may more easily increase urinary oxalate load, thereby raising the risk of stone formation or recurrence. Such groups should pay closer attention to managing both tea quantity and drinking methods. （Looking Forward New Era）
Edit：WENWEN Responsible editor：LINXUAN
Source：Beijing Youth Daily
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