Although Oolong is generally completely safe, there can be negative side effects from overconsumption. Many of these negative side effects are related to the caffeine in the tea, which, interestingly enough, is also responsible for many of the tea’s positive benefits as well.

It would take consuming an obscene amount of tea to see any of the negative side effects below, but, since this site is intended as a thorough resource, here they are:

Caffeine Drawbacks

There have been two cases of elderly patients diagnosed with hypokalemia (abnormally low serum potassium levels) that were found to be associated with excessive consumption of black and Oolong tea. Hypokalemia is a potentially life-threatening condition that has been associated with caffeine toxicity.

Excessive use of caffeine can also be linked to sleep disorders, insulin resistance, and down-graded metabolism.

Pregnancy and Lactation

Some health organizations advise pregnant women to limit their caffeine consumption to 300 mg per day. This is because high caffeine intake has been associated with an increased risk of miscarriage and low birth weights.

Oxalates

Tea contains an organic acid called oxalate which can cause kidney damage if overconsumed. Once again, this side effect is very unlikely to happen as it requires the consumption of a lot of tea.

Final Word on Oolong Tea Side Effects

Don’t be alarmed in the slightest by these side effects. The fact is, Oolong tea does vastly more good than harm, and, unless you drink enough to almost drown yourself, you won’t see any negative effects at all.