diff --git a/influxdb/_dataframe_client.py b/influxdb/_dataframe_client.py
index 4273ef1b..646f298c 100644
--- a/influxdb/_dataframe_client.py
+++ b/influxdb/_dataframe_client.py
@@ -365,16 +365,18 @@ def _convert_dataframe_to_lines(self,
 
         # Make an array of formatted field keys and values
         field_df = dataframe[field_columns]
+        # Keep the positions where Null values are found
+        mask_null = field_df.isnull().values
 
         field_df = self._stringify_dataframe(field_df,
                                              numeric_precision,
                                              datatype='field')
 
-        def format_line(line):
-            line = line[~line.isnull()]  # drop None entries
-            return ",".join((line.index + '=' + line.values))
-
-        fields = field_df.apply(format_line, axis=1)
+        field_df = (field_df.columns.values + '=').tolist() + field_df
+        field_df[field_df.columns[1:]] = ',' + field_df[
+            field_df.columns[1:]]
+        field_df = field_df.where(~mask_null, '')  # drop Null entries
+        fields = field_df.sum(axis=1)
         del field_df
 
         # Generate line protocol string
@@ -388,9 +390,6 @@ def _stringify_dataframe(dframe, numeric_precision, datatype='field'):
         # Prevent modification of input dataframe
         dframe = dframe.copy()
 
-        # Keep the positions where Null values are found
-        mask_null = dframe.isnull().values
-
         # Find int and string columns for field-type data
         int_columns = dframe.select_dtypes(include=['integer']).columns
         string_columns = dframe.select_dtypes(include=['object']).columns
@@ -435,7 +434,6 @@ def _stringify_dataframe(dframe, numeric_precision, datatype='field'):
 
         dframe.columns = dframe.columns.astype(str)
 
-        dframe = dframe.where(~mask_null, None)
         return dframe
 
     def _datetime_to_epoch(self, datetime, time_precision='s'):