From Cleveland Clinic concerning salt substitutes:
Salt substitutes are not a healthful option for everyone. Many salt substitutes contain potassium chloride in place of sodium chloride. Potassium consumed in excess may be harmful for some people. For example, many persons with kidney problems are unable to rid their bodies of excessive potassium, which could result in a deadly situation. If you have kidney problems or are on medication for your heart, kidneys or liver, it is best to check with your physician before using salt substitutes in place of sodium.
Otherwise a salt substitute containing potassium chloride is an acceptable alternative in moderation, if you do not have kidney problems and have checked with your physician to be sure it will not interact with any of your medications.
Some salt substitutes that are labeled "lite" or "low sodium" salt still contain sodium just less than amounts than actual table salt. These products often contain a mix of sodium chloride and potassium chloride. If a product is labeled "sodium free" then the main ingredient is potassium chloride with no sodium