Green tea does contain oxalates, but at lower levels than black tea or many common foods. A cup of brewed green tea typically has around 0.8 to 14 mg of oxalate per 100 mL, which puts a standard 8-ounce serving roughly in the range of 2 to 33 mg. That’s a wide range because oxalate content varies significantly depending on the tea’s origin, quality, and how you brew it.
How Green Tea Compares to Black Tea
Green tea consistently ranks as the lowest-oxalate option among true teas. One analysis published in the European Food Research and Technology journal found that green tea contained about 80 mg of oxalate per 200 mL serving, compared to 156 mg for black tea and 224 mg for dark tea. This pattern holds across multiple studies: the more oxidized the tea leaf, the higher its oxalate content. Oolong falls in the middle, with black and dark teas at the top.
The reason comes down to processing. Tea oxidation, the step that turns green leaves into black tea, generates additional oxalate. Since green tea is minimally oxidized, it retains the lowest concentrations. If you’re trying to reduce oxalate intake but don’t want to give up tea entirely, green tea is the better choice over black or oolong varieties.
Brewing Time and Temperature Matter
The oxalate that ends up in your cup depends on how you prepare it. Hotter water and longer steeping times both pull more oxalate out of the leaves. In one study measuring oxalate release at different temperatures, a tea steeped for 2 minutes at room temperature released 0.20 mg per 200 mL, while the same tea steeped for 10 minutes in boiling water released 1.08 mg. That’s more than a fivefold increase.
For practical purposes, this means shorter, cooler brews will contain less oxalate. Green tea is often recommended to be brewed at lower temperatures anyway (around 160 to 180°F rather than a full boil) to avoid bitterness, which conveniently also reduces oxalate extraction. Steeping for 2 to 3 minutes instead of 5 or more makes a measurable difference.
Most Oxalate in Green Tea Is Soluble
Oxalate in food comes in two forms: soluble and insoluble. Soluble oxalate dissolves in water and is more readily absorbed by your body, which is what matters for kidney stone risk. When you brew tea, the oxalate that ends up in your cup is predominantly the soluble form, since the insoluble portion stays trapped in the leaves. One analysis found that the soluble oxalate content of brewed green tea ranged from about 8 to 140 mg per liter, a wide spread reflecting differences in tea variety and preparation.
This is worth knowing because it means nearly all the oxalate you consume from green tea is the bioavailable kind. However, the total amount is still modest compared to high-oxalate foods like spinach, rhubarb, and nuts, which can contain hundreds of milligrams per serving.
Adding Milk Can Reduce Absorption
Calcium binds to soluble oxalate in your digestive tract, forming an insoluble compound that your body can’t absorb. This is why eating calcium-rich foods alongside oxalate-containing foods is a common strategy for people managing oxalate intake. Research on tea specifically has shown that the oxalate in black tea can bind to a significant proportion of the calcium in milk. The same principle applies to green tea: adding milk or consuming calcium-rich foods at the same time reduces the amount of free oxalate available for absorption.
This doesn’t mean you need to add milk to every cup. But if you’re drinking several cups a day and watching your oxalate levels, pairing tea with a calcium source is a simple way to offset some of the load.
Green Tea and Kidney Stone Risk
Here’s where the picture gets more interesting than you might expect. Despite containing oxalates, green tea appears to be associated with a lower risk of kidney stones, not a higher one. A case-control study of Chinese adults found that people who drank one or more cups of green tea daily had roughly 81% lower odds of being hospitalized for kidney stones compared to non-drinkers. The Shanghai Men’s and Women’s Health Study found similar results: men who consumed the most green tea had a 33% lower risk of kidney stones.
The likely explanation is that green tea increases fluid intake (which dilutes urine and helps flush the kidneys) and contains compounds that may inhibit stone formation through other mechanisms. The oxalate it contributes is relatively small in the context of a full diet, and the protective effects of hydration and other tea compounds appear to outweigh it.
That said, the evidence isn’t perfectly one-sided. At least one prospective study found that heavy tea consumption (four or more glasses per day, without distinguishing green from black) was associated with higher kidney stone risk. The type of tea, the amount consumed, and individual factors like hydration and overall diet all play a role.
Where Green Tea Fits in a Low-Oxalate Diet
The NIDDK lists spinach, rhubarb, nuts, peanuts, and wheat bran as the primary foods to limit for people with a history of calcium oxalate stones. Green tea is not on that list. For context, a half-cup of cooked spinach can contain over 750 mg of oxalate, while a cup of green tea typically delivers somewhere between 2 and 33 mg depending on preparation.
If you’re following a low-oxalate diet, a few cups of green tea per day is unlikely to be a meaningful contributor to your total oxalate load, especially if you’re also managing intake from higher-oxalate foods. Keeping your brew time short, your water temperature moderate, and your overall fluid intake high are the most practical steps to minimize any risk. For people with no history of kidney stones, green tea’s oxalate content is not a significant concern.