The question is does being a Christian immune someone from sickness? Does sin leads to sickness? Can God heal all type of sickness? If God can heal all type of sickness; why do some Christian die in sickness?

Sickness is one thing that no one ever wish to experience in life, ironically, it is one thing that no one will escape as far as this life is concerned. Being a Christian does not mean we can't sick. It will come, but how you handle it determines whether it will stay or go immediately. Yes! sickness attacked everyone but it does not stay in everybody, so stop welcoming sickness by your behavior. God perfect plan for man at creation was that we shall not know any form of corruption, but with the fall of Adam man knew corruption that has bedridden us till date. 

So long you are still on earth, you will sick when the enemy attack your health, but the good news is that God is able to heal you and will heal you if you believe. God is still in the business of restoring health to men (Jeremiah 30:17). In fact one of the best way to preach the gospel and to draw men back to God is in the healing ministry. In fact Jesus ministry and the apostle were dominated by healing from sickness (healing of the blinds, lame, fever, raising the death etc.( (Matthew 8:13; 9:29; 15:28; Act 3: 5-7; 5:1656).

When Jesus was sending the disciple out, he charged them to go preach the gospel, saying the kingdom of heaven is at hand, heal the sick, cleanse the lepers, raise the dead, cast out devils.....(Mathew 10:7-8), it means that definitely people will be sick. Sickness is certainly the result of the fall of man through Adam, but God is very much in control, and He does indeed determine how far evil can go (just as He did with Satan and Job's trials). For those who are believers and suffering with sickness, illness, and/or disease in this life, the knowledge that they can glorify God through their suffering will help; something they may not truly understand here on earth until eternity.

Sickness are mostly used to draw men back to God, the devil might meant it for bad, but God often convert it for good by healing the individuals both from the physical sickness and eternal damnation. The question is why are some Christian down with sickness and even some died of it prematurely? There are few possible causes as will be analyzed briefly below: 

Ignorance of who we are: Most Christian lack knowledge of who they are in Christ and what God can do. “My people are destroyed for lack of knowledge.”( Hosea 4:6). Satan takes advantage of many Christians because they have never been taught the simple principles of the Word of God concerning healing. Many Christian didn't know that they have power to command sickness to go and leave their body once it knocked at their door. Sickness is a spirit and has ear, so command the sickness by it name, and you see the sickness disappear. 

The truth of the matter is that Jesus is able to do all things including healing the sickness only if you believe He is able. Jesus death and wound on the cross did not only heal our sin but also our physical health. He was wounded for our transgressor, and the chastisement our sin was upon Him and by His stripe we are healed. His stripe and wound brings freedom to us from all accusation and enchantment of the devil. There are many good books, tapes, CD’s and resources that can enlighten you to the principles of God’s Word about healing. Get some and feed yourself. 

Un-believe and Fear: Fear and unbelief are the opposite of confidence and faith. All the miracle Jesus and the apostle did was done to those that believed. Yes! It takes someone with strong faith to carry a sick person to the main road to be healed by Peter shadow. Don't be amazed there are actually many sick people who Jesus were unable to heal because of their unbelief. Some will be saying in their mind, are you sure this things is real, can he heal me also? This my own case is very hard for him to do? Is not same Jesus (Person) I know? That is why Jesus was unable to do many miracles in His home town, because of their unbelief (Mathew 13:58). 

During Jesus ministry you hear Him saying in various manner that  it’s faith that receives from God: “. As you have believed, so let it be done for you” (Matthew 8:13); “.According to your faith, let it be to you” (Matthew 9:29); “.Daughter, your faith has made you well” (Mark 5:34); “.If you can believe, all things are possible to him who believes” (Mark 9:23).

There are different levels of faith: Great Faith or rugged faith; it is a kind of faith that is unshakable by whatever, it take personal conviction about the person you are believing for you to exercise such faith. (Matthew 15:28); Weak and Strong Faith; (Rom.4:19-20); Little Faith; means a worried heart  (Matt. 6:30). What we receive from the Lord is determined by the degree of faith that we are able to exercise. So people with little faith end up not receiving from God. This group of people see how big their problem is but not how big God is. Compare that your case with God, which is greater? Is it your sickness or God? If God is greater than your sickness then he will heal you. Yours might not be instant, it might be a process of healing, but be rest assured that once you believed it, you will be healed. 

Powerful faith comes through hearing God's word often and often (Roman 10:17). The more you read the bible the more your confidence on Christ is built and developed. Your faith also developed the more you hear other people testimonies, so when you hear others testimony, believe it and personalize it, thank God for the testimony and you see it come to pass in your life. 

Sin: The simple definition of sin is disobedience. Sin opens our life up to the devil to inflict us with sickness. One of the greatest weapon the bible advocate for the Christian, is the weapon of righteousness (Eph. 6:16). Isaiah 1:19, “If you are willing and obedient, you shall eat the good of the land; but if you refuse and rebel, You shall be devoured by the sword; for the mouth of the LORD has spoken. When we forsake Gods command we allow the devil to have access to us, to inflict us with all manners of sickness.

In 1 Corinthians 5: 1-5, Paul turned a young man over to the devil because he was persisting in an unrepentant way in a behavior that was causing trouble to others in the church. His unrepentant disobedience opened the door to the enemy to steal his health. We must remember that “the thief does not come except to steal, and to kill, and to destroy.”(John 10:10). Disobedience can open the door for the enemy to attack us physically. 

Negligence of the natural law: Most Christian today tends to know better than the Holy spirit and every other persons around them. Your sickness could be as a result of your disobedience to the prompting of the Holy Spirit with respect to rest, exercise and diet. If we overwork, and don’t get the proper rest our bodies need, we may open the door to the enemy to attack. If don’t treat our bodies with care by exercising and eating properly, we can open the door for sickness. If you know that mosquito causes malaria and you sleeping outside the net in a place dominated with mosquito, then you are tempting God. You need to eat hygiene food to stay healthy, that God will heal you doesn't mean you should eat anything you see or expose your body to cold and the rest of other health issues.

NOTE: There are two times Satan attacks us; when we’re in the will of God, and when we’re out of the will of God. Sickness does not only necessarily means that we have fallen astray or sinned but it could be an indication that we are humans and live in a fallen world. Also, the devil can attack us even when we live a righteous life like the case of Job in the bible. Job was not inflicted with sickness because of his sin, but because God want to use his sickness to teach others lessons. God can actually want to glorify himself in your sickness, so exercise patient with him, his strength is sufficient for you in your weakness.  

One can actually be sick and believe God for healing, yet, nothing happens, some even dies of the sickness, though in rare case. This does not mean that they did not have faith, or that God can't heal their sickness, rather God is using their infirmities to glorify His name. Just trust on him, he is able to do it and his strength is sufficient for your weakness. When you are on the sick bed trust on Christ ability, stop panicking, remove fear and anxiety and you will see yourself gradually bouncing back to life.