Can someone with a bmi of 17.7 be admitted to hospital?

It depends on the reason for the admission and the hospital's policies.

Someone with a body mass index (BMI) of 17.7 is considered to be underweight, and may be at risk of malnutrition and other health problems. However, their admission to the hospital would likely depend on the specific reason they are seeking medical care. If their symptoms or condition is severe, or if they are unable to meet their nutritional needs on an outpatient basis, they may be admitted for treatment and monitoring.

It's important to note that BMI is not the only factor considered when making decisions about hospital admissions. Other relevant factors may include the person's age, medical history, current symptoms, and the availability of appropriate treatment options.