Many universities granting B.Sc. MLS (Medical Laboratory Science) degrees require admission through an entrance exam. Generally, these are designed to cover knowledge in a variety of disciplines, such as biology, chemistry, physics, and sometimes even English, trying to measure an applicant's competence and preparedness for the degree program. Entrance exams vary with each university offering online tests to some, but others conduct their written exams.
Besides the entrance examination, some colleges consider academic and extracurricular performance. Some colleges directly admit a student based on their merit; they only check his or her qualifications in terms of marks scored in previous exams. The best option is to research the requirements at the college to which you're applying for an accurate description of what you can expect.