diff --git a/src/fmu/tools/sensitivities/_excel2dict.py b/src/fmu/tools/sensitivities/_excel2dict.py
index a89a8876..a02b96e7 100644
--- a/src/fmu/tools/sensitivities/_excel2dict.py
+++ b/src/fmu/tools/sensitivities/_excel2dict.py
@@ -161,6 +161,38 @@ def _find_onebyone_input_sheet(input_filename):
     return design_input_sheet[0]
 
 
+def _check_designinput(dsgn_input):
+    """Checks for valid input in designinput sheet"""
+
+    # Check for duplicate sensnames
+    sensitivity_names = []
+    for row in dsgn_input.itertuples():
+        if _has_value(row.sensname):
+            if row.sensname in sensitivity_names:
+                raise ValueError(
+                    "sensname '{}' was found on more than one row in designinput sheet. "
+                    "Two sensitivities can not share the same sensname. "
+                    "Please correct this and rerun".format(row.sensname)
+                )
+            else:
+                sensitivity_names.append(row.sensname)
+
+
+def _check_for_mixed_sensitivities(sens_name, sens_group):
+    """Checks for valid input in designinput sheet. A sensitivity cannot contain
+two different sensitivity types"""
+
+    types = sens_group.groupby("type", sort=False)
+    if len(types) > 1:
+        raise ValueError(
+            "The sensitivity with sensname '{}' in designinput sheet contains more "
+            "than one sensitivity type. For each sensname all parameters must be specified "
+            "using the same type (seed, scenario, dist, ref, background, extern)".format(
+                sens_name
+            )
+        )
+
+
 def _excel2dict_onebyone(input_filename, sheetnames=None):
     """Reads spesification for onebyone design
 
@@ -246,6 +278,7 @@ def _excel2dict_onebyone(input_filename, sheetnames=None):
     # Read input for sensitivities
     inputdict["sensitivities"] = OrderedDict()
     designinput = pd.read_excel(input_filename, design_inp_sheet)
+    _check_designinput(designinput)
 
     designinput["sensname"].fillna(method="ffill", inplace=True)
 
@@ -270,6 +303,8 @@ def _excel2dict_onebyone(input_filename, sheetnames=None):
     # Read each sensitivity
     for sensname, group in grouped:
 
+        _check_for_mixed_sensitivities(sensname, group)
+
         sensdict = OrderedDict()
 
         if group["type"].iloc[0] == "ref":
diff --git a/tests/test_excel2dict.py b/tests/test_excel2dict.py
index 3cd742db..906dc518 100644
--- a/tests/test_excel2dict.py
+++ b/tests/test_excel2dict.py
@@ -5,6 +5,7 @@
 from __future__ import print_function
 
 import os
+import pytest
 
 import pandas as pd
 
@@ -77,3 +78,55 @@ def test_excel2dict_design(tmpdir):
     inputdict_to_yaml(dict_design, "dictdesign.yaml")
     assert os.path.exists("dictdesign.yaml")
     assert "RMS_SEED" in "".join(open("dictdesign.yaml").readlines())
+
+
+def test_duplicate_sensname_exception(tmpdir):
+    mock_erroneous_designinput = pd.DataFrame(
+        data=[
+            ["sensname", "numreal", "type", "param_name"],
+            ["rms_seed", "", "seed"],
+            ["rms_seed", "", "seed"],
+        ]
+    )
+    tmpdir.chdir()
+    defaultvalues = pd.DataFrame()
+
+    writer = pd.ExcelWriter("designinput3.xlsx")
+    MOCK_GENERAL_INPUT.to_excel(
+        writer, sheet_name="general_input", index=False, header=None
+    )
+    mock_erroneous_designinput.to_excel(
+        writer, sheet_name="designinput", index=False, header=None
+    )
+    defaultvalues.to_excel(writer, sheet_name="defaultvalues", index=False, header=None)
+    writer.save()
+
+    with pytest.raises(
+        ValueError, match="Two sensitivities can not share the same sensname"
+    ):
+        dict_design = excel2dict_design("designinput3.xlsx")
+
+
+def test_mixed_senstype_exception(tmpdir):
+    mock_erroneous_designinput = pd.DataFrame(
+        data=[
+            ["sensname", "numreal", "type", "param_name"],
+            ["rms_seed", "", "seed"],
+            ["", "", "dist"],
+        ]
+    )
+    tmpdir.chdir()
+    defaultvalues = pd.DataFrame()
+
+    writer = pd.ExcelWriter("designinput4.xlsx")
+    MOCK_GENERAL_INPUT.to_excel(
+        writer, sheet_name="general_input", index=False, header=None
+    )
+    mock_erroneous_designinput.to_excel(
+        writer, sheet_name="designinput", index=False, header=None
+    )
+    defaultvalues.to_excel(writer, sheet_name="defaultvalues", index=False, header=None)
+    writer.save()
+
+    with pytest.raises(ValueError, match="contains more than one sensitivity type"):
+        dict_design = excel2dict_design("designinput4.xlsx")