diff --git a/litellm/integrations/prometheus.py b/litellm/integrations/prometheus.py
index bd0079cabfb..965d2792231 100644
--- a/litellm/integrations/prometheus.py
+++ b/litellm/integrations/prometheus.py
@@ -159,10 +159,16 @@ class PrometheusLogger(CustomLogger):
 
     @staticmethod
     def get_instance() -> PrometheusLogger | None:
-        """The registered PrometheusLogger, however it was registered.
+        """The live PrometheusLogger, however it was registered.
 
-        ``litellm.callbacks`` alone misses ``success_callback: ["prometheus"]``,
-        which shows up as a metric that registers and never leaves zero.
+        Two registrations have to be covered, and neither one subsumes the other.
+        An object placed in ``litellm.callbacks`` is found through the callback
+        lists. A *string* registration -- ``success_callback: ["prometheus"]``,
+        which is what the docs show -- is different: the logger is constructed
+        lazily on the first request and cached in ``_in_memory_loggers``, and
+        nothing ever adds it to a callback list. Searching only the callback
+        lists therefore returns None for the whole life of such a proxy, and
+        every metric published through here registers and never leaves zero.
         """
         import litellm
 
@@ -170,6 +176,15 @@ class PrometheusLogger(CustomLogger):
         for instance in instances:
             if isinstance(instance, PrometheusLogger):
                 return instance
+
+        # Imported here, not at module scope: litellm_logging imports this module.
+        from litellm.litellm_core_utils.litellm_logging import (
+            _in_memory_loggers,  # pyright: ignore[reportPrivateUsage]  # the only registry of lazily built loggers
+        )
+
+        for logger in _in_memory_loggers:
+            if isinstance(logger, PrometheusLogger):
+                return logger
         return None
 
     def __init__(
diff --git a/tests/test_litellm/integrations/test_prometheus_db_pool_metrics.py b/tests/test_litellm/integrations/test_prometheus_db_pool_metrics.py
index b94aaf09484..5190736ce21 100644
--- a/tests/test_litellm/integrations/test_prometheus_db_pool_metrics.py
+++ b/tests/test_litellm/integrations/test_prometheus_db_pool_metrics.py
@@ -246,6 +246,37 @@ def test_get_instance_finds_a_logger_registered_via_success_callback(logger):
         litellm.success_callback = saved_success
 
 
+def test_get_instance_finds_a_logger_registered_by_the_string_prometheus():
+    """success_callback: ["prometheus"] is the form the docs show. The logger is
+    built lazily on the first request and cached in _in_memory_loggers, and
+    nothing adds it to a callback list, so searching the callback lists alone
+    returns None for the life of the proxy and every pool metric stays at zero."""
+    import litellm
+    import litellm.litellm_core_utils.litellm_logging as litellm_logging
+    from litellm.integrations.prometheus import PrometheusLogger
+
+    saved_callbacks = litellm.callbacks
+    saved_success = litellm.success_callback
+    saved_in_memory = list(litellm_logging._in_memory_loggers)
+    try:
+        litellm.callbacks = []
+        litellm.success_callback = ["prometheus"]
+        litellm_logging._in_memory_loggers.clear()
+
+        assert PrometheusLogger.get_instance() is None, "nothing is constructed before the first request"
+
+        constructed = litellm_logging._init_custom_logger_compatible_class(
+            "prometheus", internal_usage_cache=None, llm_router=None
+        )
+
+        assert PrometheusLogger.get_instance() is constructed
+    finally:
+        litellm_logging._in_memory_loggers.clear()
+        litellm_logging._in_memory_loggers.extend(saved_in_memory)
+        litellm.callbacks = saved_callbacks
+        litellm.success_callback = saved_success
+
+
 def test_get_instance_returns_none_when_prometheus_is_not_registered(logger):
     import litellm
     from litellm.integrations.prometheus import PrometheusLogger