can my company fire me while i am on a medical leave

Yes, in many cases it is legal for a company to discharge a worker while they are off the job due to illness/injury. The reason is that in most states employment is “at-will,” meaning that a business has the right to hire and fire at any time and for any reason. Although, a dismissal must not violate the terms of any applicable union agreement or employment contract. Additionally, federal law imparts certain rights and protections to employees - it’s still illegal to fire someone for reasons related to retaliation/discrimination, and in certain cases, medical issues. The Family and Medical Leave Act (FMLA) requires that eligible workplaces allow employees 12 weeks of unpaid leave per year, either to receive medical attention for themselves or to care for a sick family member. Under the FMLA, workers cannot be fired while on medical leave. However, this law does not cover all employees, certain conditions must be met:

The FMLA only applies to business with 50 or more workers.
The employee must have worked at least 1250 hours with the company over the previous 12 months;
They must have been with the company for at least a year before taking leave;
They must be on leave for a reason covered by the FMLA; and
The employee needs to specify to their employer that they  are taking leave under the FMLA.

If any of these conditions are not met, or if the employee uses up their 12-weeks but is still unable to return to work, the employer can legally terminate them. As a general rule, it must be able to show that the worker would have been terminated even if they had not taken medical leave.  The reason for the termination should occur relatively close in time to the decision to terminate. Often, the longer the time period, the less reasonable the termination decision will appear.
That having been said, if the FMLA does not cover a worker but their condition qualifies as a disability, they may still be covered under the American Disabilities Act (ADA). Also, they may have a claim if they were on paid sick time that was part of theirr employment package at the time of the discharge.
If you that you have been wrongfully terminated, contact your state's Department of Labor and/or consulting directly with a local employment law attorney.
Here is a link to a site that will explain further:
https://employment-law.freeadvice.com/employment-law/firing/getting-fired-while-sick.htm