diff --git a/litellm/llms/anthropic/count_tokens/handler.py b/litellm/llms/anthropic/count_tokens/handler.py
index 38cd429d99a..9cdb886e5cd 100644
--- a/litellm/llms/anthropic/count_tokens/handler.py
+++ b/litellm/llms/anthropic/count_tokens/handler.py
@@ -66,8 +66,18 @@ class AnthropicCountTokensHandler(AnthropicCountTokensConfig):
 
             verbose_logger.debug("Transformed request: %s", request_body)
 
-            # Get endpoint URL
-            endpoint_url: Final = api_base or self.get_anthropic_count_tokens_endpoint()
+            # Construct clean endpoint URL handling custom proxy destinations
+            if api_base:
+                if api_base.endswith("/messages/count_tokens"):
+                    endpoint_url = api_base
+                elif api_base.endswith("/v1/messages"):
+                    endpoint_url = f"{api_base.rstrip('/')}/count_tokens"
+                elif api_base.endswith("/v1"):
+                    endpoint_url = f"{api_base.rstrip('/')}/messages/count_tokens"
+                else:
+                    endpoint_url = f"{api_base.rstrip('/')}/v1/messages/count_tokens"
+            else:
+                endpoint_url = self.get_anthropic_count_tokens_endpoint()
 
             verbose_logger.debug("Making request to: %s", endpoint_url)