diff --git a/backend/routers/medicines.py b/backend/routers/medicines.py
index b55fee7..b91be08 100644
--- a/backend/routers/medicines.py
+++ b/backend/routers/medicines.py
@@ -2,29 +2,49 @@
 from pydantic import BaseModel
 from typing import List, Optional
 from database import supabase
+from functools import lru_cache
+import math
 import random
 import time
 import urllib.request
 import json
 
-LAST_IP_LAT = 18.5204
-LAST_IP_LON = 73.8567
-IP_FETCHED = False
+DEFAULT_LOCATION = (18.5204, 73.8567)
+IP_LOCATION_URL = "https://ipwho.is/"
+
+
+def _parse_location(data):
+    if data.get("success") is False:
+        raise ValueError("IP location lookup was not successful")
+    lat = float(data.get("latitude", data.get("lat")))
+    lon = float(data.get("longitude", data.get("lon")))
+    if not (
+        math.isfinite(lat)
+        and math.isfinite(lon)
+        and -90 <= lat <= 90
+        and -180 <= lon <= 180
+    ):
+        raise ValueError("IP location response contains invalid coordinates")
+    return lat, lon
+
+
+@lru_cache(maxsize=1)
+def _fetch_ip_location():
+    req = urllib.request.Request(
+        IP_LOCATION_URL,
+        headers={'User-Agent': 'Mozilla/5.0'}
+    )
+    with urllib.request.urlopen(req, timeout=2) as response:
+        data = json.loads(response.read().decode())
+        return _parse_location(data)
+
 
 def get_default_location():
-    global LAST_IP_LAT, LAST_IP_LON, IP_FETCHED
-    if IP_FETCHED:
-        return LAST_IP_LAT, LAST_IP_LON
     try:
-        req = urllib.request.Request("http://ip-api.com/json/", headers={'User-Agent': 'Mozilla/5.0'})
-        with urllib.request.urlopen(req, timeout=2) as response:
-            data = json.loads(response.read().decode())
-            LAST_IP_LAT = data["lat"]
-            LAST_IP_LON = data["lon"]
-            IP_FETCHED = True
-            return LAST_IP_LAT, LAST_IP_LON
+        return _fetch_ip_location()
     except Exception:
-        return 18.5204, 73.8567
+        return DEFAULT_LOCATION
+
 
 def fetch_real_pharmacies(lat, lon):
     import urllib.parse
diff --git a/backend/tests/test_medicines.py b/backend/tests/test_medicines.py
new file mode 100644
index 0000000..6af2827
--- /dev/null
+++ b/backend/tests/test_medicines.py
@@ -0,0 +1,112 @@
+import importlib
+import sys
+import types
+import unittest
+from pathlib import Path
+from unittest import mock
+
+
+BACKEND_DIR = Path(__file__).resolve().parents[1]
+BACKEND_DIR_STR = str(BACKEND_DIR)
+ADDED_BACKEND_PATH = BACKEND_DIR_STR not in sys.path
+if ADDED_BACKEND_PATH:
+    sys.path.insert(0, BACKEND_DIR_STR)
+
+
+def _cleanup_import_state():
+    sys.modules.pop("routers.medicines", None)
+    if ADDED_BACKEND_PATH and BACKEND_DIR_STR in sys.path:
+        sys.path.remove(BACKEND_DIR_STR)
+
+
+unittest.addModuleCleanup(_cleanup_import_state)
+
+
+class _APIRouter:
+    def get(self, *args, **kwargs):
+        def decorator(func):
+            return func
+
+        return decorator
+
+
+class _HTTPException(Exception):
+    pass
+
+
+class _BaseModel:
+    pass
+
+
+fastapi_module = types.ModuleType("fastapi")
+fastapi_module.APIRouter = _APIRouter
+fastapi_module.HTTPException = _HTTPException
+
+pydantic_module = types.ModuleType("pydantic")
+pydantic_module.BaseModel = _BaseModel
+
+database_module = types.ModuleType("database")
+database_module.supabase = object()
+
+with mock.patch.dict(
+    sys.modules,
+    {
+        "fastapi": fastapi_module,
+        "pydantic": pydantic_module,
+        "database": database_module,
+    },
+):
+    medicines = importlib.import_module("routers.medicines")
+
+
+class DefaultLocationCacheTest(unittest.TestCase):
+    def setUp(self):
+        medicines._fetch_ip_location.cache_clear()
+
+    def test_dependency_stubs_are_scoped_to_import(self):
+        self.assertIsNot(sys.modules.get("fastapi"), fastapi_module)
+        self.assertIsNot(sys.modules.get("pydantic"), pydantic_module)
+
+    def test_default_location_fetch_is_cached_without_mutable_globals(self):
+        response = mock.Mock()
+        response.read.return_value = b'{"latitude": 12.34, "longitude": 56.78}'
+
+        with mock.patch.object(medicines.urllib.request, "urlopen") as urlopen:
+            urlopen.return_value.__enter__.return_value = response
+
+            self.assertEqual(medicines.get_default_location(), (12.34, 56.78))
+            self.assertEqual(medicines.get_default_location(), (12.34, 56.78))
+
+        self.assertEqual(urlopen.call_count, 1)
+        self.assertFalse(hasattr(medicines, "LAST_IP_LAT"))
+        self.assertFalse(hasattr(medicines, "LAST_IP_LON"))
+        self.assertFalse(hasattr(medicines, "IP_FETCHED"))
+
+    def test_default_location_falls_back_without_caching_failure(self):
+        response = mock.Mock()
+        response.read.return_value = b'{"latitude": 23.45, "longitude": 67.89}'
+        successful_lookup = mock.MagicMock()
+        successful_lookup.__enter__.return_value = response
+
+        with mock.patch.object(
+            medicines.urllib.request,
+            "urlopen",
+            side_effect=[OSError("network unavailable"), successful_lookup],
+        ) as urlopen:
+            self.assertEqual(medicines.get_default_location(), medicines.DEFAULT_LOCATION)
+            self.assertEqual(medicines.get_default_location(), (23.45, 67.89))
+
+        self.assertEqual(urlopen.call_count, 2)
+
+    def test_default_location_rejects_invalid_coordinates(self):
+        response = mock.Mock()
+        response.read.return_value = b'{"latitude": 1000, "longitude": 67.89}'
+
+        with mock.patch.object(medicines.urllib.request, "urlopen") as urlopen:
+            urlopen.return_value.__enter__.return_value = response
+
+            self.assertEqual(medicines.get_default_location(), medicines.DEFAULT_LOCATION)
+
+
+if __name__ == "__main__":
+    unittest.main()