Fatima bint Abi Hubaish used to have bleeding in between the periods, so she asked the Prophet (ﷺ) about it. He replied, "The bleeding is from a blood vessel and not the menses. So give up the prayers when the (real) menses begins and when it has finished, take a bath and start praying."
Reference: Sahih al-Bukhari 320 In-book : Book 6, Hadith 25 USC-MSA web (English) : Vol. 1, Book 6, Hadith 317 (deprecated)
Help us gift a modern, ad-free Islamic application for the Muslim Ummah. Your donation will be recorded as Sadaqah Jariyah in your book of deeds, In Sha Allah.