The answer to the title question is a resounding ‘no!’ It is impossible for a Christian to renounce Christianity and/or convert to another religion. Seven scripture references will be presented to support that truth.
Firstly, the power to retain one’s Christianity is not in the hands of the individual Christian. The power of retention is in the hands of God Himself.
“‘My sheep hear My voice, and I know them, and they follow Me. And I give them eternal life…My Father, who has given them to Me, is greater than all; and no one is able to snatch them out of My Father’s hand. I and My Father are one.’” John 10:27-30
Jesus acknowledged that there would be some who claimed to be His followers who really were not. Such are the basis of apostasy where there will be a great falling away from the church at the end of this age. This ‘falling away’ is the exiting of the apostates, i.e. those who claimed to be Christians but never bore fruit as evidence.
“Little children, it is the last hour; and as you have heard that the Anti-christ is coming, even now many anti-christs have come…They went out from us, but they were not of us; for if they had been of us, they would have continued with us…” I John 2:18-19
Jesus said the great deceiver will be granted powers to further his deception in coming days but the Christian cannot be deceived.
“For false christs and false prophets will rise and show great signs and wonders to deceive, if possible, even the elect.” Matthew 24:24
A Christian will be willing and able at all cost to remain true to his/her faith. A great example is found in the Revelation where martyrdom will be common for those unwilling to renounce their faith.
“…Then I saw the souls of those who had been beheaded for their witness to Jesus…who had not worshiped the beast or his image, and had not received his mark on their foreheads or on their hands…” Revelation 20:4
The most powerful evidence supporting the teaching that a Christian cannot renounce his/her Christianity is that the individual Christian did not choose their status with God. It was given them before their very existence.
“Blessed be the God and Father of our Lord Jesus Christ, who has blessed us with every spiritual blessing in the heavenly places in Christ, just as He chose us in Him before the foundation of the world, that we should be holy and without blame before Him in love, having predestined us to adoption as sons by Jesus Christ to Himself, according to the good pleasure of His will…” Ephesians 1:3-5
The Bible teaches that all who have been chosen by God to be conformed to the image of Christ had their names written in the Book of Life at the time they were chosen.
“All who dwell on the earth will worship him (anti-christ), whose names have not been written in the Book of Life of the Lamb slain from the foundation of the world…The beast that you saw…will ascend out of the bottomless pit and go to perdition. And those who dwell on the earth will marvel, whose names are not written in the Book of Life from the foundation of the world…” Revelation 13:8, 17:8
If one’s name is not written in the Book of Life that person has chosen to be judged by the books containing their deeds which can never satisfy a Holy and righteous God. Recall the total compatibility between man’s free choice to live or die and God’s sovereign election.
“And I saw the dead, small and great, standing before God, and the books were opened…and the dead were judged according to their works, by the things which were written in the books. And another book was opened, which is the Book of Life…and anyone not found written in the Book of Life was cast into the lake of fire.” Revelation 20:12
Therefore, all Christians had their name entered in the Book of Life before the foundation of the world and nothing can erase those names or change the immutable plan of God.