As antibiotic kill bacteria and endotoxin is released when bacteria die, wont it worsen fever or cause mild sepsis?

Depends. Yes, it can but depends on which bacteria it is and which antibiotic it is. Are you on penicillin? Please let us know as some do.
No. Antibiotics kill bacteria by different mechanisms of action. Bacteriocidal and Bacteriostatic are two ways the drugs inhibit the invading bacteria. Usually if the correct drug is chosen for the infection the patients immune system and the antibiotic work together to overcome the infection and the patient gets better.

Related Questions

I'm on clarithromycin. I'm afraid it may kill bacteria and release endotoxins to my body tissues and cause fever or mild sepsis?

Antibiotics. What are you taking it for? In general antibiotics kill susceptible bacteria and that would be cleared by the immune system of the body. There might be some mild reaction secondary to that but not severe enough to cause a concern in most of the cases. Read more...
Antibiotic concerns. If you are concerned about depleting your stores of healthy bacteria you might wish to consider taking probiotics. Read more...