A runner who collapsed and died at the 2012 London marathon had drunk an energy supplement that has since been banned, an inquest has heard.
Claire Squires, 30, of North Kilworth, Leicestershire, died less than a mile from the finish line on 22 April.
Her boyfriend, Simon van Herrewege, told an inquest that she had been using the energy supplement Jack3d while training and said she would consider taking it during the run.
The inquest confirmed that Squires had put the supplement, which contains the stimulant DMAA (dimethylamylamine), into her water bottle before the race although it is not known if she drank it.
DMAA has been linked to high blood pressure, headaches, vomiting, stroke and a death. It has been banned in Canada, Australia and New Zealand.
Dr Van Der Walt, who performed the post-mortem, said: "DMAA causes increased heart rate. On the balance of probability I think the DMAA was a contributing factor to her death".
Van Herrewege told the inquest in Southwark: "She took it a couple of times [while training] but didn't really get on with it. She never particularly liked it but wanted to beat her previous marathon time.
"She said she was going to take one scoop, as recommended. In her own words: 'If I hit a bit of a wall, I might take this drink and see if it pushes me through to the end of the marathon'," he said.
Van Herrewege added that she had purchased the supplement online.
In August, four months after Squires's death, the Medicines and Healthcare Products Regulatory Agency removed the product from the market over safety fears about the DMAA.
The inquest heard how Squires's acupuncturist had confirmed that she had an irregular heartbeat in 2011 but the runner had not mentioned the condition to her family, doctor, or boyfriend.
The 30-year-old hairdresser had originally raised £650 for the Samaritans via her justgiving.com page before the race. Following the news of her death, this figure rocketed to over £1m.
The Claire Squires Fund is a programme of projects that reflect how the runner would have donated the money.