diff --git a/simglucose/envs/simglucose_gym_env.py b/simglucose/envs/simglucose_gym_env.py
index 59410055..58acc741 100644
--- a/simglucose/envs/simglucose_gym_env.py
+++ b/simglucose/envs/simglucose_gym_env.py
@@ -21,24 +21,21 @@ class T1DSimEnv(gym.Env):
     '''
     metadata = {'render.modes': ['human']}
 
+    SENSOR_HARDWARE = 'Dexcom'
+    INSULIN_PUMP_HARDWARE = 'Insulet'
+
     def __init__(self, patient_name=None, reward_fun=None):
         '''
         patient_name must be 'adolescent#001' to 'adolescent#010',
         or 'adult#001' to 'adult#010', or 'child#001' to 'child#010'
         '''
-        seeds = self._seed()
         # have to hard code the patient_name, gym has some interesting
         # error when choosing the patient
         if patient_name is None:
             patient_name = 'adolescent#001'
-        patient = T1DPatient.withName(patient_name)
-        sensor = CGMSensor.withName('Dexcom', seed=seeds[1])
-        hour = self.np_random.randint(low=0.0, high=24.0)
-        start_time = datetime(2018, 1, 1, hour, 0, 0)
-        scenario = RandomScenario(start_time=start_time, seed=seeds[2])
-        pump = InsulinPump.withName('Insulet')
-        self.env = _T1DSimEnv(patient, sensor, pump, scenario)
+        self.patient_name = patient_name
         self.reward_fun = reward_fun
+        self.seed()
 
     def _step(self, action):
         # This gym only controls basal insulin
@@ -59,6 +56,14 @@ def _seed(self, seed=None):
         # 2**31.
         seed2 = seeding.hash_seed(seed1 + 1) % 2**31
         seed3 = seeding.hash_seed(seed2 + 1) % 2**31
+
+        hour = self.np_random.randint(low=0.0, high=24.0)
+        start_time = datetime(2018, 1, 1, hour, 0, 0)
+        patient = T1DPatient.withName(self.patient_name)
+        sensor = CGMSensor.withName(self.SENSOR_HARDWARE, seed=seed2)
+        scenario = RandomScenario(start_time=start_time, seed=seed3)
+        pump = InsulinPump.withName(self.INSULIN_PUMP_HARDWARE)
+        self.env = _T1DSimEnv(patient, sensor, pump, scenario)
         return [seed1, seed2, seed3]
 
     def _render(self, mode='human', close=False):
diff --git a/tests/test_seed.py b/tests/test_seed.py
new file mode 100644
index 00000000..3691da28
--- /dev/null
+++ b/tests/test_seed.py
@@ -0,0 +1,30 @@
+import gym
+import unittest
+from simglucose.controller.basal_bolus_ctrller import BBController
+from datetime import datetime
+
+
+class TestSeed(unittest.TestCase):
+    def test_changing_seed_generates_different_results(self):
+        from gym.envs.registration import register
+        register(
+            id='simglucose-adolescent2-v0',
+            entry_point='simglucose.envs:T1DSimEnv',
+            kwargs={'patient_name': 'adolescent#002'}
+        )
+
+        env = gym.make('simglucose-adolescent2-v0')
+
+        env.seed(0)
+        observation_seed0 = env.reset()
+        self.assertEqual(env.env.scenario.start_time, datetime(2018, 1, 1, 16, 0, 0))
+
+        env.seed(1000)
+        observation_seed1 = env.reset()
+        self.assertEqual(env.env.scenario.start_time, datetime(2018, 1, 1, 10, 0, 0))
+
+        self.assertNotEqual(observation_seed0, observation_seed1)
+
+
+if __name__ == '__main__':
+    unittest.main()