My daily urine output for a 24 hours is 4.5liter for a fluid intake of around 2.8 liter also has a sudden urge to urinate, my urologist is saying my kidney is functioning correctly based on electrolyte blood test is he right. do i need nephrologist?

Get the app Cronometer and track the water content of everything you eat/drink. And then see if this matches your urine output. If you are not getting up at night to pee kidneys likely. Fluid that goes in must come out or u gain weight. Out includes sweat(sensible and insensible) spit, stool, lungs and urine. Google these and then use Cronometer to track. It should add up.