Faulty glucose sensor led to insulin overdose and Zverev's Halle loss

Alexander Zverev's first tournament since winning Roland Garros ended in the Halle semifinals after a malfunctioning glucose monitor caused him to overdose on insulin, leaving the German struggling physically throughout the 2-hour‑39-minute match against Taylor Fritz.

The sensor that I wear gave me a completely incorrect reading. It showed very high values when in reality they were low. I injected much more insulin than I should have.

What happened in the match

Zverev, a type‑1 diabetic, relies on a continuous glucose sensor to manage his blood sugar during play. On Saturday the device, which he has used since 2016 or 2017, told him his glucose was dangerously high just before the warm‑up. Acting on that reading, he injected a large dose of insulin. Shortly afterwards, his team confirmed that his sugar was actually low, but by then the excess insulin was already taking effect.

To avoid hypoglycemia, Zverev downed one glucose gel after another during the opening set. Within the first 45 minutes he had taken in roughly 350 grams of sugar – roughly the equivalent of 3.5 liters of Coca‑Cola. He still won the first set 7‑6(4), but his physical state deteriorated. Fritz took the second set 6‑4 and broke serve late in the third to close out a 7‑6(4), 4‑6, 7‑5 victory. Zverev had also needed treatment for a back spasm after 40 minutes, but he insisted the back was not the decisive factor.

In nine years I had never seen such a big error. If anyone watches the match, they will see me drinking one glucose drink after another. It’s like drinking three and a half liters of Coca‑Cola during a match. I felt terrible.

The broader context

The defeat snapped a 10‑match winning streak that had begun at Roland Garros, where Zverev captured his first Grand Slam title on 7 June. It was also his seventh straight loss to Fritz. Frances Tiafoe later defeated Fritz 6‑4, 6‑4 in the final to become the first American champion in the 33‑year history of the Halle event and claim his maiden ATP 500 crown.

Outlook for Wimbledon

Zverev stressed that the sensor fault was an isolated incident and that he remains optimistic ahead of Wimbledon, which starts on 29 June. He pointed to his overall level on grass in Halle as a positive sign. Organisers and fans will watch his health closely, but Zverev’s camp considers the diabetes management equipment reliable despite Saturday’s rare malfunction.