diff --git a/pandas/core/algorithms.py b/pandas/core/algorithms.py
index 21d12d02c9008..5cc3afbae92d3 100644
--- a/pandas/core/algorithms.py
+++ b/pandas/core/algorithms.py
@@ -320,6 +320,7 @@ def unique(values):
     of appearance. This does NOT sort.
 
     Significantly faster than numpy.unique. Includes NA values.
+    For numeric input, the dtype of the result will be promoted to 64-bit.
 
     Parameters
     ----------
diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 598c4dca9ce88..b669475531f10 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -2122,6 +2122,7 @@ def dropna(self, how="any"):
         Returns
         -------
         Index without duplicates
+        For numeric input, the dtype of the result will be promoted to 64-bit.
 
         See Also
         --------
diff --git a/pandas/core/series.py b/pandas/core/series.py
index 4e64a25e430eb..a3f0bfaaf8fd0 100644
--- a/pandas/core/series.py
+++ b/pandas/core/series.py
@@ -1910,8 +1910,9 @@ def unique(self):
 
         Notes
         -----
-        Returns the unique values as a NumPy array. In case of an
-        extension-array backed Series, a new
+        Returns the unique values as a NumPy array.
+        For numeric input, the dtype of the result will be promoted to 64-bit.
+        In case of an extension-array backed Series, a new
         :class:`~api.extensions.ExtensionArray` of that type with just
         the unique values is returned. This includes