Some Christians hold to a false teaching that committing suicide automatically prevents one from going to Heaven. Many believe that a Christian who commits suicide will not be saved. This teaching is not supported in the Bible. If this were true - then God would be breaking a promise to us.
Scripture teaches that, from the moment we truly believe in Christ, we are guaranteed eternal life (John 3:16). According to the Bible, Christians can know beyond any doubt that they possess eternal life (1 John 5:13). Nothing can separate a Christian from God’s love (Romans 8:38–39).
No “created thing” can separate a Christian from God’s love, and even a Christian who commits suicide is a “created thing”; therefore, not even suicide can separate a Christian from God’s love. Jesus died for all of our sins, and if a true Christian, in a time of spiritual attack and weakness, commits suicide, his sin is still covered by the blood of Christ.
It is also a fool's game to try and gauge another's faith. Belief is belief. The extent or measure of the belief does not take one to a higher or lower place. To have faith is to have doubts.
The Bible lists only one unpardonable sin - and that is blasphemy of the Holy Spirit. This is willingly turning your back on God. Past this God does not rank sins... although people like to think he does. Suicide is not the “greatest” sin—it is no worse than other evils, in terms of how God sees it, and it does not determine whether or not a person goes to hell. However, suicide definitely has a deep and lasting impact on those left behind. The painful scars left by a suicide do not heal easily.
No one truly knows what was happening in a person’s heart the moment he or she died. Some people have “deathbed conversions” and accept Christ in the moments before death. It is possible that a suicide could have a last-second change of heart and cry out for God’s mercy. We leave such judgments to God (1 Samuel 16:7). The suicide of a believer is evidence that anyone can struggle with despair and that our enemy, Satan, is “a murderer from the beginning” (John 8:44).