The fast commences during the dawn and closes during the dusk. Puja is done both in the morning and evening. Typically, this can be observed for six months continuously starting from the Tamil Months of Adi and Thai. Observing the vrat for 12 years continuously is said to bestow the devotees with the incomparable great fortune of having the vision of Lord Subrahmanya. The vrat consists of total abstinence from food and if strict vrat is not possible, the devotee can take some fruits and milk offered to the Lord.
Masik Karthigai vrat cleanses the system and cures incurable diseases. The devotee obtains a clear vision in life and achieves protection against the evil and enemies with the grace of Lord Subrahmanya. Visiting the temples of Lord Subrahmanya on Masik Karthigai can give added benefits. All pujas and vrat addressed to Lord Muruga can automatically win the blessings of Lord Shiva and Mother Parvati also. Therefore the Masik Karthigai Vrat is considered highly efficacious from several points of view.