Lucy Sidwells, 29, of Pelsall near Walsall has secured a charity place for the event on October 2 in aid of the Epilepsy Society and has to raise a minimum of £2,500.
She explained that she donned her training shoes and decided to apply to race to help the charity after her own life was turned upside down when her condition was finally diagnosed.
Lucy said: "I am a midwife working in the NHS at New Cross Hospital in Wolverhampton. I was finally diagnosed with epilepsy in August 2019 after three major tonic-clonic seizures resulted in me ending up in A&E resus at Walsall Manor Hospital.
"I had spent over 20 years also having complex partial and absence seizures that were dismissed by healthcare professionals.
"My life has been turned upside down since diagnosis in many ways such as losing my driving licence and unfortunately despite several medications the seizures are still not under control."
Lucy says due to the the Epilepsy Society providing her with vital physical and emotional support she has been able to continue to working full time.
"This is a once in a lifetime opportunity for me to run the London Marathon for the leading epilepsy charity for research and support and give back what I can," she said.
"I would be extremely grateful if anyone is able to donate to help me reach the £2,500 target."
Her training schedule included running three times a week around her work shifts, comprising some three to five miles and longer run of six to10 mile runs.
She added: "My training is going well. I plan to start an official marathon countdown training plan at the end of May. Until then I want to continue my three runs a week and work on pacing ready for the marathon."
To support her challenge visit the website justgiving.com/fundraising/lucy-sidwells