The Thames and one of its London tributaries were contaminated with a mixture of five drugs.
Researchers from the University of York tested river water in 72 countries to measure the level of 14 commonly used antibiotics.
The researchers compared the monitoring data with "safe" levels, which is depending on the antibiotic, range from 20 ng/l to 32,000 ng/l.
Drugs get into rivers via human and animal waste, as well as leaks from wastewater treatment and drug manufacturing sources. In the worst cases - found in countries including Bangladesh, Ghana and Kenya - levels were hundreds of times higher than the levels deemed safe.
Overuse and misuse of the drugs are thought to be the main causes of antimicrobial resistance.
Professor Alistair Boxall, Theme Leader of the York Environmental Sustainability Institute, is quoted as saying describing the results as "quite eye-opening and worrying, demonstrating the widespread contamination of river systems around the world with antibiotic compounds".
Quadro Graphics Driver 430.86 Made Available by NVIDIA - Download Now
Inside is Intel's Core i9-9880H processor, NVIDIA Quadro RTX 5000 graphics, 32GB of RAM , and 1TB of NVMe SSD storage . The first RTX Studio Laptop should be available this June, and the pricing is expected to start at around $1,599.
Overall, antibiotics concentration in the country's rivers was 170 times higher than the prescribed limit.
The UN has announced that the rise of antibiotic-resistant bacteria is a global health emergency and it could kill over 10 million people by 2050.
Sites where antibiotics exceeded safe levels were most often found in Asia and Africa, but also at sites in Europe, with researchers calling it a "global problem".
Dealing with the logistical challenge of transporting 92 samples collected from various rivers around the world, researchers managed to fly back frozen samples to the University of York for testing.
Dr John Wilkinson, from the Department of Environment and Geography, who co-ordinated the monitoring work said no other study had been done on this scale. Earlier studies were from Europe, North America and China, and only a handful of antibiotics have been tested for.
An assessment of antibiotic pollution in rivers across the world shows that the concentration of antibiotics in some rivers is much higher than what is considered safe. "Our data show that antibiotic contamination of rivers could be an important contributor".
Solving the problem of antibiotic pollution in the natural environment is going to be a massive challenge, Boxall warns.
The finds are due to be unveiled during two presentations at the annual meeting of the Society of Environmental Toxicology and Chemistry (SETAC) in Helsinki on 27 and 28 May.