Yes, tea is one of the highest-oxalate beverages you can drink. A single cup of black tea contains roughly 156 mg of oxalate, and some varieties exceed 300 mg per cup. For context, people on a low-oxalate diet (typically those with a history of kidney stones) are advised to keep their entire daily intake below 40 to 50 mg. That means one cup of certain teas can deliver several times the recommended daily limit on its own.
Not all teas are equal, though. The type of tea, how long you steep it, and even the specific brand can shift oxalate levels dramatically.
Oxalate Levels by Tea Type
Dark teas like pu-erh top the list, averaging about 224 mg of oxalate per 200 mL cup. Black teas come next at around 156 mg per cup. Green tea is considerably lower, averaging about 80 mg per cup, though some flavored green teas test as low as 49 mg.
The range within each category is wide. Among black teas, an Earl Grey tested at 304 mg per cup, nearly double the black tea average. A single pu-erh variety hit 342 mg per cup. So the specific product you buy matters as much as the general category. If you’re tracking oxalate intake, it’s worth knowing that “black tea” can mean anywhere from roughly 100 mg to over 300 mg depending on the brand and blend.
Why Some Teas Have More Than Others
Tea plants naturally accumulate oxalate in their leaves as they mature. Black and dark teas are generally made from older, more mature leaves, which have had more time to build up oxalate. Green teas and white teas tend to use younger leaves and buds, which is one reason their oxalate content runs lower. Processing also plays a role: the heavy fermentation and oxidation involved in making dark teas like pu-erh may concentrate oxalate further compared to the lighter processing of green tea.
Brewing Time Changes the Numbers
The longer you steep your tea, the more oxalate ends up in your cup. Research measuring oxalate across different steeping times found that a 5-minute brew released about 4.4 mg per cup, while steeping the same tea for a full 60 minutes pushed levels to 6.3 mg. Most of the increase happens in the first 15 minutes. After that, additional steeping time extracts oxalate at a much slower rate.
This means a quick 3- to 5-minute steep will keep oxalate levels at the lower end for any given tea. Leaving a tea bag sitting in your mug all morning, on the other hand, pulls out noticeably more.
Herbal Teas Are a Different Story
Herbal “teas” aren’t made from the Camellia sinensis plant, so their oxalate profiles are completely separate from true tea. Ginger tea, for instance, contains only about 0.26 mg of oxalate per 100 g of the dried herb, a negligible amount. Rooibos, chamomile, and peppermint are also generally considered low-oxalate options, though published data on exact milligram values for these is limited.
If you enjoy the ritual of a hot drink but need to keep oxalate low, herbal teas are the most practical swap. Just be aware that some herbal blends include actual tea leaves, which would add oxalate back in. Check the ingredients list.
What This Means for Kidney Stones
Oxalate binds with calcium in the kidneys to form calcium oxalate stones, the most common type of kidney stone. For most healthy people who have never had a stone, moderate tea consumption isn’t a major concern because the body handles dietary oxalate without issue. The risk rises for people who have already formed calcium oxalate stones or who have been told they excrete high levels of oxalate in their urine.
On a low-oxalate diet capped at 40 to 50 mg per day, even a single cup of black tea could use up your entire daily budget or blow past it. Green tea is more manageable but still significant at around 80 mg per cup. The math simply doesn’t work for heavy tea drinkers on a restricted diet.
Practical Ways to Reduce Oxalate From Tea
If you want to keep drinking tea while lowering your oxalate exposure, a few adjustments help:
- Switch to green tea. It averages about half the oxalate of black tea per cup.
- Steep for less time. Keeping your brew under 5 minutes limits how much oxalate dissolves into the water.
- Add milk or a calcium source. Calcium binds to oxalate in the gut before it reaches the kidneys. Drinking tea with milk may reduce the amount of oxalate your body actually absorbs.
- Limit yourself to one cup. Two or three cups a day multiplies your oxalate load quickly, especially with black tea.
- Try herbal alternatives. Rooibos, ginger, chamomile, and peppermint deliver a warm drink with minimal oxalate.
Staying well hydrated throughout the day also dilutes oxalate in the urine, reducing the chance that it crystallizes into stones regardless of how much tea you drink.