diff --git a/changelog.d/549.changed.md b/changelog.d/549.changed.md
new file mode 100644
index 00000000..37ca9e04
--- /dev/null
+++ b/changelog.d/549.changed.md
@@ -0,0 +1 @@
+Raise the first simulation cache memory warning from 8 GiB to 16 GiB while retaining the 32 GiB warning.
diff --git a/src/policyengine/core/cache.py b/src/policyengine/core/cache.py
index 410301e4..4761ff2f 100644
--- a/src/policyengine/core/cache.py
+++ b/src/policyengine/core/cache.py
@@ -6,7 +6,7 @@
 
 logger = logging.getLogger(__name__)
 
-_MEMORY_THRESHOLDS_GB = [8, 16, 32]
+_MEMORY_THRESHOLDS_GIB = [16, 32]
 _warned_thresholds: set[int] = set()
 
 T = TypeVar("T")
@@ -50,10 +50,11 @@ def _check_memory_usage(self) -> None:
         process = psutil.Process()
         memory_gb = process.memory_info().rss / (1024**3)
 
-        for threshold in _MEMORY_THRESHOLDS_GB:
+        for threshold in _MEMORY_THRESHOLDS_GIB:
             if memory_gb >= threshold and threshold not in _warned_thresholds:
                 logger.warning(
-                    f"Memory usage has reached {memory_gb:.2f}GB (threshold: {threshold}GB). "
+                    f"Memory usage has reached {memory_gb:.2f} GiB "
+                    f"(threshold: {threshold} GiB). "
                     f"Cache contains {len(self._cache)} items."
                 )
                 _warned_thresholds.add(threshold)
diff --git a/tests/test_cache.py b/tests/test_cache.py
index cb16ef65..4839551e 100644
--- a/tests/test_cache.py
+++ b/tests/test_cache.py
@@ -1,10 +1,13 @@
 import os
 import tempfile
+from types import SimpleNamespace
 
 import pandas as pd
+import pytest
 from microdf import MicroDataFrame
 
 from policyengine.core import Simulation
+from policyengine.core import cache as cache_module
 from policyengine.core.cache import LRUCache
 from policyengine.tax_benefit_models.uk import (
     PolicyEngineUKDataset,
@@ -143,3 +146,74 @@ def test_lru_cache_clear():
     assert cache.get("a") is None
     assert cache.get("b") is None
     assert cache.get("c") is None
+
+
+@pytest.mark.parametrize("memory_gib", [0, 8, 15.99])
+def test_lru_cache_does_not_warn_below_16_gib(
+    monkeypatch: pytest.MonkeyPatch,
+    caplog: pytest.LogCaptureFixture,
+    memory_gib: float,
+) -> None:
+    cache_module._warned_thresholds.clear()
+    monkeypatch.setattr(
+        cache_module.psutil,
+        "Process",
+        lambda: SimpleNamespace(
+            memory_info=lambda: SimpleNamespace(rss=memory_gib * 1024**3)
+        ),
+    )
+
+    with caplog.at_level("WARNING", logger=cache_module.__name__):
+        LRUCache[str]().add("key", "value")
+
+    assert caplog.records == []
+
+
+def test_lru_cache_warns_once_at_16_gib_and_again_at_32_gib(
+    monkeypatch: pytest.MonkeyPatch,
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    cache_module._warned_thresholds.clear()
+    memory = SimpleNamespace(gib=16.0)
+    monkeypatch.setattr(
+        cache_module.psutil,
+        "Process",
+        lambda: SimpleNamespace(
+            memory_info=lambda: SimpleNamespace(rss=memory.gib * 1024**3)
+        ),
+    )
+    cache = LRUCache[str]()
+
+    with caplog.at_level("WARNING", logger=cache_module.__name__):
+        cache.add("first", "value")
+        cache.add("second", "value")
+        memory.gib = 32.0
+        cache.add("third", "value")
+
+    messages = [record.getMessage() for record in caplog.records]
+    assert len(messages) == 2
+    assert "threshold: 16 GiB" in messages[0]
+    assert "threshold: 32 GiB" in messages[1]
+
+
+def test_lru_cache_clear_resets_memory_warning_state(
+    monkeypatch: pytest.MonkeyPatch,
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    cache_module._warned_thresholds.clear()
+    monkeypatch.setattr(
+        cache_module.psutil,
+        "Process",
+        lambda: SimpleNamespace(memory_info=lambda: SimpleNamespace(rss=16 * 1024**3)),
+    )
+    cache = LRUCache[str]()
+
+    with caplog.at_level("WARNING", logger=cache_module.__name__):
+        cache.add("first", "value")
+        cache.clear()
+        cache.add("second", "value")
+
+    assert (
+        sum("threshold: 16 GiB" in record.getMessage() for record in caplog.records)
+        == 2
+    )