The woman was cycling on Silverknowes Road, Edinburgh, when she was involved in a collision at about 10.20am on Thursday, 29 April.
It remains unclear as to whether or not there were other vehicles involved.
The road was only recently altered with a cycle lane to make it safer for cyclists.
Emergency services attended and the woman was taken to Royal Infirmary of Edinburgh where medical staff have described her condition as critical.
Officers have issued an appeal to find out more about the circumstances surrounding the crash.
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A witness said a section of the road was cordoned off during the incident.
A police spokeswoman said: “No other vehicles are believed to have been involved at this stage and enquiries are ongoing to establish the full circumstances surrounding the incident.
“Anyone with information is asked to contact Police Scotland through 101, quoting incident number 1233 of Thursday, 29 April. Anyone with information is asked to contact Police Scotland through 101, quoting incident number 1233 of Thursday, 29 April.”