Is Green Tea High in Oxalates? A Comprehensive Guide

December 4, 2025 •

4 min read

While some popular beverages contain significant oxalates, brewed green tea typically contains much less than its black tea counterpart. For most healthy individuals, the oxalate content in moderate amounts of green tea is not a concern, but for those with a history of kidney stones, understanding the levels is crucial. This comprehensive guide explains the key differences and factors to consider.

Quick Summary

Green tea has a moderate oxalate content, considerably lower than black tea. The amount is influenced by the type, harvest, and preparation, especially relevant for those managing dietary oxalates.

Key Points

Moderate Oxalate Content: Brewed green tea contains a moderate amount of oxalates, significantly lower than black tea.
Matcha is an Exception: Matcha contains high levels of oxalates because you consume the entire powdered leaf, unlike a standard brewed tea.
Factors Affecting Levels: Oxalate content in green tea varies based on processing (fermentation increases it), harvest time, and cultivation methods (shading).
Preparation Matters: To reduce oxalate intake, consider adding a calcium source like milk or performing a short pre-infusion before the main brew.
Potential Benefits: Despite containing oxalates, green tea's antioxidants like EGCG may help inhibit the formation of calcium oxalate kidney stones.
General Safety: For most healthy adults, green tea's oxalate content is not a major concern when consumed in moderation.
High-Risk Individuals: Those with a history of kidney stones should be mindful of their overall oxalate intake and consult a doctor.

Oxalates are naturally occurring compounds found in many plants, including tea leaves. When you consume them, they can bind with calcium in the digestive tract and get excreted, but excessive intake in sensitive individuals can contribute to the formation of calcium oxalate kidney stones. The key to managing oxalate intake from tea lies in understanding the processing and preparation methods.

What Influences Oxalate Levels in Green Tea?

Several factors can cause the oxalate content in green tea to vary, which is why a single, definitive number is often misleading. These include:

Tea Type and Processing

Not all green teas are created equal. Different processing methods used for various tea types result in different oxalate levels. Fermentation, for instance, significantly increases oxalate content, which is why black teas contain much higher levels than non-fermented green teas.

Shading and Harvest Time

Certain premium Japanese green teas, such as Gyokuro and Tencha, are shade-grown, a process that slightly increases their oxalate levels compared to unshaded teas like Sencha. Additionally, studies have shown that leaves harvested in the autumn tend to have more oxalate than the younger, smaller spring leaves.

Preparation Method

How you prepare your tea can affect the final oxalate concentration in your cup. Steeping duration has been shown to have only a slight influence on the final oxalate concentration in green tea. However, as oxalates are highly soluble, a longer steep time will generally release more of the compound into the infusion. A key distinction must also be made for matcha.

Why Matcha is Different from Brewed Green Tea

Matcha is a powdered green tea where the entire tea leaf is consumed, not just the infusion. This means that when you drink matcha, you ingest all the oxalates present in the leaf, making its oxalate content significantly higher than a standard cup of brewed green tea. Individuals with oxalate sensitivity or a history of kidney stones should consume matcha in moderation and consider this difference carefully.

Comparison of Oxalate Content in Common Teas


Beverage Type	Preparation Method	Oxalate Content (approximate range)
Brewed Black Tea	Infused	3-16 mg per cup (240mL)
Brewed Green Tea	Infused	2-35 mg per cup (250mL), varies widely
Oolong Tea	Infused	<1 mg per cup
Matcha	Whole Leaf Powder	Highest oxalate of green tea types
Herbal Teas	Infused	Low, but varies depending on ingredients
Spinach	Serving	Very high (970 mg per 100g)

Ways to Reduce Oxalate Intake from Tea

For those needing to monitor their oxalate consumption, there are several simple strategies to consider:

Add milk or a calcium source: The calcium in milk or other sources can bind to oxalates in the gut, reducing absorption. A study also showed a pre-infusion step can significantly reduce oxalate in tea bags.
Pre-infuse tea bags: Research has shown that a short pre-infusion of a tea bag before the main brew can remove a significant percentage of the soluble oxalate, reducing overall intake without affecting the taste.
Choose lower-oxalate teas: Non-fermented teas like green tea and oolong generally contain less oxalate than black tea. Herbal teas made from non-oxalate-rich ingredients are also a safe bet.
Limit matcha consumption: Due to its high oxalate content, moderation is key for matcha drinkers, especially if managing a low-oxalate diet.
Stay hydrated: Drinking plenty of water is one of the best preventative measures against kidney stone formation, as it helps to dilute the concentration of oxalates and other compounds in the urine.

Green Tea, Antioxidants, and Kidney Health

Interestingly, some research suggests that despite its oxalate content, green tea may actually be beneficial for preventing kidney stone formation, particularly those made of calcium oxalate. This is attributed to its high concentration of antioxidants, such as epigallocatechin gallate (EGCG), which has been shown to inhibit crystal formation. However, this effect is dose-dependent and does not negate the need for a low-oxalate diet in sensitive individuals. The anti-oxidative properties of green tea may protect against stone formation, but excessive consumption should still be avoided.

Conclusion

In conclusion, the claim that is green tea high in oxalates? is an oversimplification. While it does contain oxalates, brewed green tea is not considered a high-oxalate beverage for the average person, especially compared to black tea or high-oxalate foods like spinach. The total oxalate load and individual sensitivity are what matter most. For individuals concerned about kidney stones, moderation, choosing lower-oxalate varieties (like oolong), and adjusting preparation methods can help manage intake. Furthermore, green tea's potential antioxidant benefits should also be considered, but consulting a healthcare professional for personalized dietary advice is always recommended for those with specific health conditions.

For more in-depth research on how pre-infusion can reduce oxalate content in tea, you can read studies available on platforms like PubMed.

Frequently Asked Questions

For most people, drinking green tea in moderation is not a risk factor for kidney stones. In fact, some studies suggest that the antioxidants in green tea may even help inhibit stone formation. However, individuals with a history of calcium oxalate kidney stones should monitor their total oxalate intake from all food and drink sources and consult a healthcare provider.

Oolong tea and some herbal teas generally contain lower amounts of oxalates than green or black tea. For instance, brewed oolong tea has been reported to contain less than 1 mg of oxalate per cup, while many herbal varieties are very low.

Yes, matcha is considered high in oxalates compared to regular brewed green tea. This is because matcha is made from the entire powdered tea leaf, meaning you consume all the compounds present, including oxalates, rather than just the brewed infusion.

One effective method is to perform a short pre-infusion, or a quick rinse, of the tea bag before the main brew. The initial infusion removes a significant amount of soluble oxalates. Additionally, adding milk to your tea can help bind to oxalates, reducing their absorption.

Studies have shown that modifying the steeping duration of green tea leaves has no significant influence on the oxalate content of the beverage. While longer steeps for black tea may increase oxalates, the effect is much less pronounced for green tea.

Brewed green tea has a much lower oxalate content than brewed black tea. Black tea undergoes a fermentation process that increases its oxalate concentration, making it a greater concern for individuals on a low-oxalate diet.

While green tea has potential benefits due to its antioxidants, individuals with kidney problems, particularly a history of kidney stones, should speak with a doctor or registered dietitian. Moderate consumption is often acceptable, but it's essential to consider your overall diet and individual health needs.

Some studies suggest that compounds in green tea, like EGCG, can inhibit the formation of calcium oxalate crystals, potentially offering a protective effect against kidney stones. However, this does not eliminate the presence of oxalates, and the overall impact depends on dosage and individual health. The relationship is complex and still under investigation.