Exodus 20:13 (CSBBible)
Do not murder.

Euthanasia is a fancy and roundabout way of committing murder.
The Bible does not specifically discuss euthanasia. However, what it does say about life and death offers a balanced perspective. Causing death is unacceptable, but there is no requirement to go to desperate lengths to prolong life during the dying process.
God cursed Caine in Genesis 4 for killing his brother Abel but put a mark on Caine to stop anyone from killing him and promises to punish anyone who does. It is clear throughout the scriptures that life and death are fully God’s fields according to Acts 17:28 and Psalm 36:9.
Euthanasia is the termination of life to achieve some concept of good, such as putting an end to physical suffering. It could be death by choice or the choice of other people. It may be called death by dignity, mercy killing, assisted suicide and death selection.
In God’s eyes, life is very precious. For this reason, God condemns both taking the life of another and taking one’s own life. According to 1 John 3:15, Whoever hates his brother is a murderer.
And no murderer hath eternal life (except for the repentant) because God cannot dwell in the heart where hatred and malice dwell.
Any number of the people in the bible with sickness, disabilities, and suffering, could have taken this route out of their predicament but if they were born in this era, who knows what they will have done: Job, the woman with the issue of blood, the sick and crippled people of Jesus’s time all needed relief.
God ordained a natural order for ending life and beginning the next, but euthanasia opposes the sovereignty of God in His creations. God ordains the days of our lives as stated in Psalm 139:16. Death is inevitable, Psalm 89:48 states that we will all see death soon, so active euthanasia is murder.
Every believer should leave mortality in God’s hand. We can’t and do not own life, it is a gift from God, none of us has the power to control life or death according to Ecclesiastes 8:8, true ownership of life belongs to God and it is His choice, not that of an individual or society when life should end, it is God gracious responsibility to creates, sustains and cares for life at every stage – pre-born, infancy, adolescence, maturity and old age as seen in Job 14:5.
Someone might say they have the right to die because this life is no longer bearable. How are you sure that wherever you are going is going to be bearable-heaven or hell?
Nobody has the right to take something that does not belong to them.
It is healthy to want to preserve life and natural to not want to prolong death but why would someone prematurely take their life in their hands just to escape what Hebrew 9:27 says is inevitable?
Ecclesiastes 7:14 states that sometimes God allows us to suffer for a long time before death occurs; other times, one’s suffering is short. No one enjoys suffering though, but that does not make it right to determine that a person should die when death is already a natural occurrence.
Life is valuable to the Lord! Cherish it!
Shalom