diff --git a/litellm/caching/in_memory_cache.py b/litellm/caching/in_memory_cache.py
index 6b40c48c4ef..785bc5a68ec 100644
--- a/litellm/caching/in_memory_cache.py
+++ b/litellm/caching/in_memory_cache.py
@@ -62,13 +62,12 @@ class InMemoryCache(BaseCache):
         try:
             # Fast path for common primitive types that are typically small
             if (
-                isinstance(value, (bool, int, float, str))
+                isinstance(value, (bool, int, float))
                 and len(str(value)) < self.max_size_per_item * MAX_SIZE_PER_ITEM_IN_MEMORY_CACHE_IN_KB
             ):  # Conservative estimate
                 return True
 
-            # Direct size check for bytes objects
-            if isinstance(value, bytes):
+            if isinstance(value, (str, bytes)):
                 return sys.getsizeof(value) / 1024 <= self.max_size_per_item
 
             # Handle special types without full conversion when possible
diff --git a/tests/unit/caching/test_in_memory_cache.py b/tests/unit/caching/test_in_memory_cache.py
index 901832937b5..c62b1828cd1 100644
--- a/tests/unit/caching/test_in_memory_cache.py
+++ b/tests/unit/caching/test_in_memory_cache.py
@@ -117,6 +117,28 @@ def test_in_memory_cache_max_size_per_item():
     assert result is False
 
 
+@pytest.mark.parametrize(
+    ("character", "count", "should_cache"),
+    [
+        ("a", 100, True),
+        ("\u00e9", 100, True),
+        ("\u6f22", 100, True),
+        ("\U0001f600", 100, True),
+        ("a", 1023, False),
+        ("\u00e9", 1023, False),
+        ("\u6f22", 600, False),
+        ("\U0001f600", 300, False),
+    ],
+)
+def test_string_cache_admission_respects_byte_size(character: str, count: int, should_cache: bool) -> None:
+    cache: Final = InMemoryCache(max_size_per_item=1, clock=lambda: 1000.0)
+    value: Final = character * count
+
+    cache.set_cache("text", value)
+
+    assert cache.get_cache("text") == (value if should_cache else None)
+
+
 def test_in_memory_cache_ttl():
     """
     Check that