diff --git a/hed/models/column_source.py b/hed/models/column_source.py
index 9f3453cb..0a2f7312 100644
--- a/hed/models/column_source.py
+++ b/hed/models/column_source.py
@@ -11,7 +11,7 @@
 
 from __future__ import annotations
 
-import math
+import numbers
 from typing import Protocol, runtime_checkable
 
 # Cell texts that mean "no value here". None and float NaN are also missing.
@@ -45,11 +45,18 @@ def distinct_values(values) -> dict[str, list[int]]:
 
 
 def is_missing(value) -> bool:
-    """Return True if a cell value stands for "no value": None, a float NaN, ``""`` or ``"n/a"``."""
+    """Return True if a cell value stands for "no value": None, a NaN of any float width, ``""`` or ``"n/a"``.
+
+    The NaN test accepts any real number rather than only ``float``: numpy's float32 and float16 do not
+    subclass Python's float (only float64 does), and a numpy-backed table (an NWB column, a pandas
+    frame read with a narrow dtype) hands those NaNs over as values. NaN is the one real value that is
+    not equal to itself, and that test needs no conversion to float, so an integer too large for a
+    float or a Fraction is simply a value.
+    """
     if value is None:
         return True
-    if isinstance(value, float) and math.isnan(value):
-        return True
+    if isinstance(value, numbers.Real):
+        return bool(value != value)
     return isinstance(value, str) and value in MISSING_VALUES
 
 
diff --git a/tests/models/test_column_source.py b/tests/models/test_column_source.py
index 10b8d38c..a99f8e1b 100644
--- a/tests/models/test_column_source.py
+++ b/tests/models/test_column_source.py
@@ -1,9 +1,12 @@
 import math
 import unittest
+from fractions import Fraction
 
+import numpy as np
 import pandas as pd
 
 from hed.models import ColumnSource, ListColumnSource, TabularInput, distinct_values
+from hed.models.column_source import is_missing
 
 
 class TestDistinctValues(unittest.TestCase):
@@ -15,6 +18,27 @@ def test_missing_values_are_dropped(self):
         values = [None, float("nan"), "", "n/a", "Red", math.nan, "n/a"]
         self.assertEqual(distinct_values(values), {"Red": [4]})
 
+    def test_numpy_nan_of_any_width_is_missing(self):
+        """numpy float32 and float16 are not instances of float; their NaN is still a missing value."""
+        for dtype in (np.float16, np.float32, np.float64):
+            values = np.array([1.5, np.nan, 1.5], dtype=dtype)
+            self.assertEqual(distinct_values(values), {"1.5": [0, 2]}, dtype)
+            self.assertTrue(is_missing(values[1]), dtype)
+            self.assertFalse(is_missing(values[0]), dtype)
+        self.assertFalse(is_missing(np.int32(0)))
+        self.assertFalse(is_missing(np.bool_(False)))
+        self.assertFalse(is_missing(0))
+        self.assertTrue(is_missing(None))
+        self.assertTrue(is_missing("n/a"))
+        self.assertFalse(is_missing("nan"))  # the text nan is a value
+
+    def test_real_values_that_do_not_fit_a_float_are_values(self):
+        """An integer too large for a float, or a Fraction, is a value: the NaN test converts nothing."""
+        huge = 10**1000
+        self.assertFalse(is_missing(huge))
+        self.assertFalse(is_missing(Fraction(1, 3)))
+        self.assertEqual(distinct_values([huge, Fraction(1, 3), huge]), {str(huge): [0, 2], "1/3": [1]})
+
     def test_non_strings_become_text_and_bytes_are_decoded(self):
         values = [3, 3.5, b"Blue", 3]
         self.assertEqual(distinct_values(values), {"3": [0, 3], "3.5": [1], "Blue": [2]})