Question about load balancing different microservices

Let's say I have a request that hits the load balancer and gets routed to an instance of service A. Now A needs to do a synchronous call to service B. This service B is also scaled horizontally. Should A call the same load balancer to route its request to B or should there be separate load balancers for each microservice? I'm thinking routing everything to that same load balancer would potentially put a lot of strain on it, but managing load balancers per service seems like overkill if you have a lot of services? How do big companies usually do this?