diff --git a/eureka_ml_insights/data_utils/transform.py b/eureka_ml_insights/data_utils/transform.py
index 4d163630..6597b355 100644
--- a/eureka_ml_insights/data_utils/transform.py
+++ b/eureka_ml_insights/data_utils/transform.py
@@ -433,12 +433,14 @@ class ExtractUsageTransform:
     Extracts token usage completion numbers (except prompt input tokens) for all models.
     args:
         model_config: config used for the experiment.
-        usage_completion_output_col: str, default name of the column where completion numbers will be stored for all models
-        prepend_completion_read_col: str, prepend string to add to the name of the usage column from which to read. Useful for cases when the usage column might have been renamed earlier in the pipeline.
+        usage_completion_output_col: str, default name of the column where completion numbers will be stored for model
+        usage_column: str, default name of the column where usage information is stored for model
+        n_tokens_column: str, default name of the column where number of tokens is stored for model
     """
     model_config: ModelConfig
     usage_completion_output_col: str = "usage_completion" 
-    prepend_completion_read_col: str = "" 
+    usage_column: str = "usage"
+    n_tokens_column: str = "n_output_tokens" 
 
     def transform(self, df: pd.DataFrame) -> pd.DataFrame:
         """
@@ -448,7 +450,7 @@ def transform(self, df: pd.DataFrame) -> pd.DataFrame:
             df (pd.DataFrame): Input dataframe of inference results retrieved with the model_config.
 
         Returns:
-            pd.DataFrame: Transformed dataframe with completion token numbers in completion_usage_col.
+            pd.DataFrame: Transformed dataframe with completion token numbers in usage_completion_output_col.
         """
         usage_completion_read_col = None
         if (self.model_config.class_name is GeminiModel):
@@ -469,10 +471,35 @@ def transform(self, df: pd.DataFrame) -> pd.DataFrame:
             logging.warn(f"Model {self.model_config.class_name} is not recognized for extracting completion token usage.")
         # if the model is one for which the usage of completion tokens is known, use that corresponding column for the model
         # otherwise, use the default "n_output_tokens" which is computed with a universal tokenizer as shown in TokenCounterTransform()
+        self.validate(df, usage_completion_read_col)
         if usage_completion_read_col:
-            df[self.usage_completion_output_col] = df[self.prepend_completion_read_col + "usage"].apply(lambda x: x[usage_completion_read_col])
-        elif self.prepend_completion_read_col + "n_output_tokens" in df.columns:
-            df[self.usage_completion_output_col] = df[self.prepend_completion_read_col + "n_output_tokens"]
+            df[self.usage_completion_output_col] = df.apply(lambda x: self._extract_usage(x, usage_completion_read_col), axis=1)
+        elif self.n_tokens_column in df.columns:
+            df[self.usage_completion_output_col] = df[self.n_tokens_column]
         else:
             df[self.usage_completion_output_col] = np.nan
         return df 
+    
+    def validate(self, df: pd.DataFrame, usage_completion_read_col: str) -> pd.DataFrame:
+        """Check that usage_columns or n_tokens_columns are present actually in the data frame.
+        Args:
+            df (pd.DataFrame): Input dataframe containing model_output_col and id_col.
+            usage_completion_read_col (str): The column name for token extraction.
+        """
+        if usage_completion_read_col and self.usage_column not in df.columns:
+            raise ValueError(f"The {self.usage_column} column is not present in the data frame.")
+        elif self.n_tokens_column not in df.columns:
+            raise ValueError(f"The {self.n_tokens_column} column is not present in the data frame.")
+
+    def _extract_usage(self, row, usage_completion_read_col):
+        """
+        Extracts the token usage for a given row if usage column and corresponding completion column exists. 
+        Args:
+            row (pd.Series): A row of the dataframe.
+            usage_completion_read_col (str): The column name to extract the token usage from.
+        Returns:
+            int: The token usage for the row.
+        """
+        if not pd.isna(row[self.usage_column]) and usage_completion_read_col in row[self.usage_column]:
+            return row[self.usage_column][usage_completion_read_col]
+        return np.nan
diff --git a/tests/test_utils.py b/tests/test_utils.py
index dc8ae164..824bbabb 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -51,7 +51,8 @@ def __init__(self):
 
     def generate(self, text_prompt, query_images=None):
         return {"model_output": random.choice(["Final Answer: A", "Final Answer: B", "Final Answer: C", "Final Answer: D"]), 
-                "is_valid": random.choice([True, False])}
+                "is_valid": random.choice([True, False]),
+                "n_output_tokens": 3}
 
     def name(self):
         return self.name
@@ -111,7 +112,9 @@ def __init__(self, model_name="generic_test_model"):
         self.name = model_name
 
     def generate(self, text_prompt, *args, **kwargs):
-        return {"model_output": "Generic model output", "is_valid": random.choice([True, False])}
+        return {"model_output": "Generic model output", 
+                "is_valid": random.choice([True, False]),
+                "n_output_tokens": 3}
 
 
 class DNAEvaluationInferenceTestModel: