diff --git a/litellm/llms/anthropic.py b/litellm/llms/anthropic.py
index 150ae0e07..829a8becd 100644
--- a/litellm/llms/anthropic.py
+++ b/litellm/llms/anthropic.py
@@ -20,7 +20,7 @@ class AnthropicError(Exception):
         self.status_code = status_code
         self.message = message
         self.request = httpx.Request(
-            method="POST", url="https://api.anthropic.com/v1/complete"
+            method="POST", url="https://api.anthropic.com/v1/messages"
         )
         self.response = httpx.Response(status_code=status_code, request=self.request)
         super().__init__(
@@ -35,9 +35,7 @@ class AnthropicConfig:
     to pass metadata to anthropic, it's {"user_id": "any-relevant-information"}
     """
 
-    max_tokens_to_sample: Optional[
-        int
-    ] = litellm.max_tokens  # anthropic requires a default
+    max_tokens: Optional[int] = litellm.max_tokens  # anthropic requires a default
     stop_sequences: Optional[list] = None
     temperature: Optional[int] = None
     top_p: Optional[int] = None
@@ -46,7 +44,7 @@ class AnthropicConfig:
 
     def __init__(
         self,
-        max_tokens_to_sample: Optional[int] = 256,  # anthropic requires a default
+        max_tokens: Optional[int] = 256,  # anthropic requires a default
         stop_sequences: Optional[list] = None,
         temperature: Optional[int] = None,
         top_p: Optional[int] = None,
@@ -124,6 +122,10 @@ def completion(
             model=model, messages=messages, custom_llm_provider="anthropic"
         )
 
+    for message in messages:
+        if message["role"] == "system":
+            message["role"] = "assistant"
+
     ## Load Config
     config = litellm.AnthropicConfig.get_config()
     for k, v in config.items():
@@ -134,7 +136,7 @@ def completion(
 
     data = {
         "model": model,
-        "prompt": prompt,
+        "messages": messages,
         **optional_params,
     }
 
@@ -173,7 +175,7 @@ def completion(
 
         ## LOGGING
         logging_obj.post_call(
-            input=prompt,
+            input=messages,
             api_key=api_key,
             original_response=response.text,
             additional_args={"complete_input_dict": data},
@@ -192,19 +194,14 @@ def completion(
                 status_code=response.status_code,
             )
         else:
-            if len(completion_response["completion"]) > 0:
-                model_response["choices"][0]["message"][
-                    "content"
-                ] = completion_response["completion"]
+            text_content = completion_response["content"][0].get("text", None)
+            model_response.choices[0].message.content = text_content  # type: ignore
             model_response.choices[0].finish_reason = completion_response["stop_reason"]
 
         ## CALCULATING USAGE
-        prompt_tokens = len(
-            encoding.encode(prompt)
-        )  ##[TODO] use the anthropic tokenizer here
-        completion_tokens = len(
-            encoding.encode(model_response["choices"][0]["message"].get("content", ""))
-        )  ##[TODO] use the anthropic tokenizer here
+        prompt_tokens = completion_response["usage"]["input_tokens"]
+        completion_tokens = completion_response["usage"]["output_tokens"]
+        total_tokens = prompt_tokens + completion_tokens
 
         model_response["created"] = int(time.time())
         model_response["model"] = model
diff --git a/litellm/main.py b/litellm/main.py
index 67586603d..9fbd1b828 100644
--- a/litellm/main.py
+++ b/litellm/main.py
@@ -1023,7 +1023,7 @@ def completion(
                 api_base
                 or litellm.api_base
                 or get_secret("ANTHROPIC_API_BASE")
-                or "https://api.anthropic.com/v1/complete"
+                or "https://api.anthropic.com/v1/messages"
             )
             custom_prompt_dict = custom_prompt_dict or litellm.custom_prompt_dict
             response = anthropic.completion(
diff --git a/litellm/tests/test_completion.py b/litellm/tests/test_completion.py
index f6be6e952..200b0ae58 100644
--- a/litellm/tests/test_completion.py
+++ b/litellm/tests/test_completion.py
@@ -84,6 +84,22 @@ def test_completion_claude():
 # test_completion_claude()
 
 
+def test_completion_claude_3():
+    litellm.set_verbose = True
+    messages = [{"role": "user", "content": "Hello, world"}]
+    try:
+        # test without max tokens
+        response = completion(
+            model="anthropic/claude-3-opus-20240229",
+            messages=messages,
+            max_tokens=10,
+        )
+        # Add any assertions, here to check response args
+        print(response)
+    except Exception as e:
+        pytest.fail(f"Error occurred: {e}")
+
+
 def test_completion_mistral_api():
     try:
         litellm.set_verbose = True
diff --git a/litellm/utils.py b/litellm/utils.py
index b3e197c1a..173f5e79e 100644
--- a/litellm/utils.py
+++ b/litellm/utils.py
@@ -4200,7 +4200,7 @@ def get_optional_params(
         if top_p is not None:
             optional_params["top_p"] = top_p
         if max_tokens is not None:
-            optional_params["max_tokens_to_sample"] = max_tokens
+            optional_params["max_tokens"] = max_tokens
     elif custom_llm_provider == "cohere":
         ## check if unsupported param passed in
         supported_params = [