diff --git a/instructor/exceptions.py b/instructor/exceptions.py
new file mode 100644
index 0000000..b36bd9f
--- /dev/null
+++ b/instructor/exceptions.py
@@ -0,0 +1,6 @@
+class IncompleteOutputException(Exception):
+    """Exception raised when the output from LLM is incomplete due to max tokens limit reached."""
+
+    def __init__(self, message="The output is incomplete due to a max_tokens length limit."):
+        self.message = message
+        super().__init__(self.message)
\ No newline at end of file
diff --git a/instructor/function_calls.py b/instructor/function_calls.py
index 3def9a0..4bef31f 100644
--- a/instructor/function_calls.py
+++ b/instructor/function_calls.py
@@ -1,6 +1,7 @@
 from docstring_parser import parse
 from functools import wraps
 from pydantic import BaseModel, create_model
+from instructor.exceptions import IncompleteOutputException
 
 import enum
 
@@ -121,6 +122,9 @@ class OpenAISchema(BaseModel):
         Returns:
             cls (OpenAISchema): An instance of the class
         """
+        if completion.choices[0].finish_reason == 'length':
+            raise IncompleteOutputException()
+      
         if stream_multitask:
             return cls.from_streaming_response(completion, mode)
 
@@ -179,6 +183,9 @@ class OpenAISchema(BaseModel):
         Returns:
             cls (OpenAISchema): An instance of the class
         """
+        if completion.choices[0].finish_reason == 'length':
+            raise IncompleteOutputException()
+        
         if stream_multitask:
             return await cls.from_streaming_response_async(completion, mode)
 
@@ -225,4 +232,4 @@ def openai_schema(cls) -> OpenAISchema:
             cls.__name__,
             __base__=(cls, OpenAISchema),
         )
-    )  # type: ignore
+    )  # type: ignore
\ No newline at end of file
diff --git a/tests/test_function_calls.py b/tests/test_function_calls.py
index b5447d3..6514f04 100644
--- a/tests/test_function_calls.py
+++ b/tests/test_function_calls.py
@@ -1,8 +1,50 @@
 import pytest
 from pydantic import BaseModel
+from openai.resources.chat.completions import ChatCompletion
 
-from instructor import openai_schema, OpenAISchema
+from instructor import openai_schema, OpenAISchema, Mode
+from instructor.exceptions import IncompleteOutputException
 
+@pytest.fixture
+def test_model():
+    class TestModel(OpenAISchema):
+        name: str = "TestModel"
+        data: str
+
+    return TestModel
+  
+@pytest.fixture
+def mock_completion(request):
+    finish_reason = 'stop'
+    data_content = "{\n\"data\": \"complete data\"\n}"
+
+    if hasattr(request, 'param'):
+        finish_reason = request.param.get('finish_reason', finish_reason)
+        data_content = request.param.get('data_content', data_content)
+
+
+    mock_choices = [{
+        "index": 0,
+        "message": {
+            "role": "assistant",
+            "function_call": {
+                "name": "TestModel",
+                "arguments": data_content
+            },
+            "content": data_content,
+        },
+        "finish_reason": finish_reason
+    }]
+
+    completion = ChatCompletion(
+        id="test_id",
+        choices=mock_choices,
+        created=1234567890,
+        model="gpt-3.5-turbo",
+        object="chat.completion",
+    )
+    
+    return completion
 
 def test_openai_schema():
     @openai_schema
@@ -40,3 +82,23 @@ def test_no_docstring():
         Dummy.openai_schema["description"]
         == "Correctly extracted `Dummy` with all the required parameters with correct types"
     )
+
+@pytest.mark.parametrize('mock_completion', [{'finish_reason': 'length', 'data_content': '{\n\"data\": \"incomplete dat\"\n}'}], indirect=True)
+def test_incomplete_output_exception(test_model, mock_completion):
+    with pytest.raises(IncompleteOutputException):
+        test_model.from_response(mock_completion)
+        
+def test_complete_output_no_exception(test_model, mock_completion):
+    test_model_instance = test_model.from_response(mock_completion)
+    assert test_model_instance.data == "complete data"
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize('mock_completion', [{'finish_reason': 'length', 'data_content': '{\n\"data\": \"incomplete dat\"\n}'}], indirect=True)
+async def test_incomplete_output_exception(test_model, mock_completion):
+    with pytest.raises(IncompleteOutputException):
+        await test_model.from_response(mock_completion)
+        
+@pytest.mark.asyncio
+async def test_complete_output_no_exception(test_model, mock_completion):
+    test_model_instance = await test_model.from_response_async(mock_completion)
+    assert test_model_instance.data == "complete data"
\ No newline at end of file