Alexander Zverev has revealed that a malfunctioning glucose monitor triggered a dangerous blood-sugar episode during his semi-final loss at the Terra Wortmann Open in Halle, a health scare that overshadowed his final grass-court tune-up before Wimbledon.
The German, who manages type 1 diabetes diagnosed in childhood, was beaten 6-7 (4), 6-4, 7-5 by American Taylor Fritz on Saturday. It was a seventh straight defeat to Fritz, who now leads their head-to-head 10-5 and ended Zverev’s 10-match winning run — a streak unbroken since the 29-year-old lifted his maiden major title at Roland Garros earlier this month.
But the result was quickly eclipsed by Zverev’s explanation of what unfolded behind the scoreline. The world No. 3 said the sensor he wears to track his levels gave a reading shortly before the match that was at odds with how he felt physically. Believing the device, he over-corrected with insulin, only to confirm moments later that his blood sugar was in fact running low.
“I had huge problems with my blood sugar today,” Zverev told reporters after the match, adding that the incorrect reading prompted him to inject too much insulin before walking on court.
The consequences played out early in the contest. Trailing 3-4 in the opening set and level at deuce on his own serve, Zverev stopped play and was granted an off-court medical timeout. He recovered to edge a tight first set on a tie-break, but faded physically as Fritz levelled and then pulled clear in the decider.
To stop his levels falling to what he described as dangerously low, Zverev said he had to consume roughly 350 grams of sugar inside the first 45 minutes — an intake he likened to drinking “300 litres of Coke during a match.” He said he felt physically absent through the middle of the contest and could not produce the level he believed his game was capable of.
Zverev acknowledged he was also managing a back issue during the match but stressed the sensor failure was the more significant problem. Crucially, he said he had never experienced a malfunction of this severity before, framing it as an isolated equipment failure rather than a recurring concern — an important distinction with the year’s third major now days away.
Across the net, Fritz sensed something was wrong without knowing the cause. The American, who struck 19 aces and won the bulk of his first-serve points, said afterward that he felt physically stronger than his opponent and told himself to keep working through the closing stages.
For Zverev, the timing is delicate. He is projected to be seeded No. 2 at Wimbledon behind defending champion and world No. 1 Jannik Sinner, his ranking and status boosted further by Carlos Alcaraz’s withdrawal from the grass-court swing with a wrist injury. Yet the All England Club has long been his most stubborn puzzle: Zverev has never advanced beyond the fourth round at Wimbledon, falling at that stage in 2017, 2021 and 2024, and has never won a grass-court title despite reaching finals in Halle and Stuttgart.
Despite the defeat, the German struck a notably upbeat tone about his form on the surface, saying he had played good grass-court tennis in Halle and would carry positive feelings into London. He emphasised the short turnaround that defines this stretch of the calendar, with Wimbledon following almost immediately, and said his priority now is preparation rather than dwelling on the result.
Fritz advanced to Sunday’s final against compatriot Frances Tiafoe, an all-American title match on grass and further evidence of the Californian’s strong pre-Wimbledon form after he also reached the Stuttgart final.
The Wimbledon main draw begins on 29 June. For Zverev, the priority between now and then will be ensuring his monitoring set-up is watertight — and that an avoidable equipment fault does not resurface on the sport’s biggest stage.
