Why does the Luckin coffee Fair Isle Latte affect people so differently?

Luckin Coffee's Fair Isle Latte combines espresso with Ceylon black tea and tastes close to Assam milk tea. Some drinkers report sleeping poorly after one cup, along with hand tremors, dizziness, and heart palpitations, and a few sought emergency care. Others who wanted an energy boost said it did nothing and left them drowsy.

Reactions appear to track individual caffeine tolerance. The drink stacks caffeine from espresso with tea polyphenols from black tea, so people who rarely consume either may feel the effect far more strongly than daily coffee drinkers. The split feedback has turned the launch into a debate about how much caffeine a single tea-coffee drink carries.

Luckin Coffee's recently launched Fair Isle Latte has quickly become a new favorite among some office workers and tea-coffee enthusiasts, thanks to its flavor reminiscent of Assam milk tea and its powerful energizing effect. However, a large number of "avoid at all costs" posts have emerged on social media, with many consumers reporting that they couldn't sleep all night after drinking it, and even experienced symptoms such as hand tremors, dizziness, and heart palpitations—some even sought emergency medical care late at night. Meanwhile, netizens who were seeking an energizing effect tried it and said it had no effect at all, leaving them still drowsy. This starkly divided feedback has plunged this new drink—a blend of espresso and Ceylon black tea—into controversy. This article will sort through the various viewpoints, explore the impact of differences in caffeine tolerance, and offer professional advice from Front Street Coffee.

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Not long ago, Luckin Coffee launched a Fair Isle Latte with a wintry vibe. It tastes somewhat similar to Assam milk tea, yet its energizing power far exceeds expectations, earning it favor among some tea-coffee enthusiasts and office workers, who have made it their recent weekday "regular companion."

However, recently many posts have appeared on social media reminding people to "think twice before trying the Fair Isle Latte." The posters said that after drinking this new Luckin product, they found it hard to fall asleep. Some joked, "Still counting Fair Isles at 3 a.m.," while others lamented, "The coffee went down at 8 p.m., and I only fell asleep at 8 a.m." Many complained that this new drink's wake-up effect was far beyond expectations—one cup could keep a person awake all night.

Besides insomnia, some consumers reported experiencing hand tremors, dizziness, nausea, and other discomfort after trying this tea-coffee drink, with a few even experiencing a racing heartbeat, palpitations, and more severe symptoms. Some claimed they had to go to the emergency room that very night after drinking it.

These netizens who experienced adverse reactions speculated that Luckin's Fair Isle Latte contains both espresso and Ceylon black tea, and it was likely the dual effect of "caffeine + tea polyphenols" that caused such obvious rejection reactions in their bodies.

However, for those who need caffeine to stay awake, what they want is exactly a drink that can keep them alert. So after seeing these posts, netizens seeking an energizing effect became curious instead, immediately placing orders to try it and verify whether, as the "victims" claimed, one cup could make them fully energized in no time.

To their frustration, after drinking this Fair Isle Latte, the insomnia, palpitations, and other discomfort mentioned by other users did not occur in them—but neither did they get a clear mind. Instead, they reported: "Drank it in the morning and still dozed off in class," and "Coffee + a big red envelope... still desperately sleepy."

In response to this situation, some netizens pointed out that although the Fair Isle Latte contains both black tea and coffee, and the caffeine content in the drink is indeed not low, everyone's constitution is different, so reactions after drinking will naturally vary. Some people who are more sensitive to caffeine may have already exceeded their tolerance before finishing a single cup, and their bodies send out alarm signals, causing adverse reactions such as a racing heartbeat and palpitations.

But for office workers and students who can't go a day without coffee, long-term drinking habits have given them a certain tolerance to caffeine. Therefore, after drinking this beverage with both tea and coffee, they won't stay awake all night—instead, they "still feel sleepy" and are basically unaffected.

Based on these situations, some users believe that although the effect of a cup of tea-coffee varies from person to person, a large number of negative feedback posts about the Fair Isle Latte have already appeared on social media. Luckin Coffee might consider labeling the caffeine content and possible drinking risks in the drink's description, to prevent consumers unfamiliar with the new product from experiencing physical discomfort after trying it.

At the same time, they suggest that people who rarely drink coffee beverages and those with caffeine intolerance should purchase with caution. If they feel dizzy or nauseous after trying it, they should stop after a small sip and not force themselves to finish the cup.

Image source: Xiaohongshu

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