What is obligatory for one who broke her fast during the day in Ramadan for a blood test and was unable to defecate until after breaking her fast, then she thought she had to make up the day but forgot about it until the next Ramadan came?

Taking a blood sample for analysis does not invalidate the fast. However, it is not permissible to break the fast for pre-employment (istiqdām) analyses if they can be performed at night. If it is not possible and a dire need depends on it, such as earning a livelihood, then breaking the fast is permissible to the extent of the necessity. The day on which the fast was broken must be made up before the next Ramadan. If it was not made up due to forgetfulness, then only making it up is obligatory.