diff --git a/README.md b/README.md
index 699c368..1f34552 100644
--- a/README.md
+++ b/README.md
@@ -62,7 +62,7 @@ Requirements:
 - Name Length 1-255 characters
 - Name must be ASCII characters only
 - Values must be in the range of 8.515920e-109 to 1.174271e+108. In addition, special values (for example, NaN, +Infinity, -Infinity) are not supported.
-- Units must meet CW Metrics unit requirements, if not it will default to None. See [MetricDatum](https://docs.aws.amazon.com/AmazonCloudWatch/latest/APIReference/API_MetricDatum.html) for valid values.
+- Metrics must meet CloudWatch Metrics requirements, otherwise a `InvalidMetricError` will be thrown. See [MetricDatum](https://docs.aws.amazon.com/AmazonCloudWatch/latest/APIReference/API_MetricDatum.html) for valid values.
 
 Examples:
 
@@ -102,6 +102,7 @@ Requirements:
 
 - Length 1-255 characters
 - ASCII characters only
+- Dimensions must meet CloudWatch Dimensions requirements, otherwise a `InvalidDimensionError` or `DimensionSetExceededError` will be thrown. See [Dimensions](https://docs.aws.amazon.com/AmazonCloudWatch/latest/APIReference/API_Dimension.html) for valid values.
 
 Examples:
 
@@ -122,6 +123,7 @@ Requirements:
 
 - Length 1-255 characters
 - ASCII characters only
+- Dimensions must meet CloudWatch Dimensions requirements, otherwise a `InvalidDimensionError` or `DimensionSetExceededError` will be thrown. See [Dimensions](https://docs.aws.amazon.com/AmazonCloudWatch/latest/APIReference/API_Dimension.html) for valid values.
 
 Examples:
 
@@ -157,6 +159,7 @@ Requirements:
 
 - Name Length 1-255 characters
 - Name must be ASCII characters only
+- Namespace must meet CloudWatch Namespace requirements, otherwise a `InvalidNamespaceError` will be thrown. See [Namespaces](https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/cloudwatch_concepts.html#Namespace) for valid values.
 
 Examples:
 
diff --git a/aws_embedded_metrics/constants.py b/aws_embedded_metrics/constants.py
index 0b975b7..af2ac16 100644
--- a/aws_embedded_metrics/constants.py
+++ b/aws_embedded_metrics/constants.py
@@ -12,6 +12,11 @@
 # limitations under the License.
 
 DEFAULT_NAMESPACE = "aws-embedded-metrics"
-MAX_DIMENSION_SET_SIZE = 30
 MAX_METRICS_PER_EVENT = 100
 MAX_DATAPOINTS_PER_METRIC = 100
+MAX_DIMENSION_SET_SIZE = 30
+MAX_DIMENSION_NAME_LENGTH = 250
+MAX_DIMENSION_VALUE_LENGTH = 1024
+MAX_METRIC_NAME_LENGTH = 1024
+MAX_NAMESPACE_LENGTH = 256
+VALID_NAMESPACE_REGEX = '^[a-zA-Z0-9._#:/-]+$'
diff --git a/aws_embedded_metrics/exceptions.py b/aws_embedded_metrics/exceptions.py
index 2747924..2ca0f8d 100644
--- a/aws_embedded_metrics/exceptions.py
+++ b/aws_embedded_metrics/exceptions.py
@@ -15,3 +15,21 @@ class DimensionSetExceededError(Exception):
     def __init__(self, message: str) -> None:
         # Call the base class constructor with the parameters it needs
         super().__init__(message)
+
+
+class InvalidDimensionError(Exception):
+    def __init__(self, message: str) -> None:
+        # Call the base class constructor with the parameters it needs
+        super().__init__(message)
+
+
+class InvalidMetricError(Exception):
+    def __init__(self, message: str) -> None:
+        # Call the base class constructor with the parameters it needs
+        super().__init__(message)
+
+
+class InvalidNamespaceError(Exception):
+    def __init__(self, message: str) -> None:
+        # Call the base class constructor with the parameters it needs
+        super().__init__(message)
diff --git a/aws_embedded_metrics/logger/metrics_context.py b/aws_embedded_metrics/logger/metrics_context.py
index 13a30c0..1b4db2b 100644
--- a/aws_embedded_metrics/logger/metrics_context.py
+++ b/aws_embedded_metrics/logger/metrics_context.py
@@ -14,9 +14,8 @@
 
 from aws_embedded_metrics import constants, utils
 from aws_embedded_metrics.config import get_config
-from aws_embedded_metrics.constants import MAX_DIMENSION_SET_SIZE
-from aws_embedded_metrics.exceptions import DimensionSetExceededError
 from aws_embedded_metrics.logger.metric import Metric
+from aws_embedded_metrics.validator import validate_dimension_set, validate_metric
 from typing import List, Dict, Any, Set
 
 
@@ -50,6 +49,7 @@ def put_metric(self, key: str, value: float, unit: str = None) -> None:
         context.put_metric("Latency", 100, "Milliseconds")
         ```
         """
+        validate_metric(key, value, unit)
         metric = self.metrics.get(key)
         if metric:
             # TODO: we should log a warning if the unit has been changed
@@ -57,15 +57,6 @@ def put_metric(self, key: str, value: float, unit: str = None) -> None:
         else:
             self.metrics[key] = Metric(value, unit)
 
-    @staticmethod
-    def validate_dimension_set(dimensions: Dict[str, str]) -> None:
-        """
-        Validates dimension set length is not more than MAX_DIMENSION_SET_SIZE
-        """
-        if len(dimensions) > MAX_DIMENSION_SET_SIZE:
-            raise DimensionSetExceededError(
-                f"Maximum number of dimensions per dimension set allowed are {MAX_DIMENSION_SET_SIZE}")
-
     def put_dimensions(self, dimension_set: Dict[str, str]) -> None:
         """
         Adds dimensions to the context.
@@ -77,7 +68,7 @@ def put_dimensions(self, dimension_set: Dict[str, str]) -> None:
             # TODO add ability to define failure strategy
             return
 
-        self.validate_dimension_set(dimension_set)
+        validate_dimension_set(dimension_set)
 
         # Duplicate dimension sets are removed before being added to the end of the collection.
         # This ensures only latest dimension value is used as a target member on the root EMF node.
@@ -99,7 +90,7 @@ def set_dimensions(self, dimension_sets: List[Dict[str, str]], use_default: bool
         self.should_use_default_dimensions = use_default
 
         for dimension_set in dimension_sets:
-            self.validate_dimension_set(dimension_set)
+            validate_dimension_set(dimension_set)
 
         self.dimensions = dimension_sets
 
diff --git a/aws_embedded_metrics/logger/metrics_logger.py b/aws_embedded_metrics/logger/metrics_logger.py
index e9caa04..e5f5708 100644
--- a/aws_embedded_metrics/logger/metrics_logger.py
+++ b/aws_embedded_metrics/logger/metrics_logger.py
@@ -13,6 +13,7 @@
 
 from aws_embedded_metrics.environment import Environment
 from aws_embedded_metrics.logger.metrics_context import MetricsContext
+from aws_embedded_metrics.validator import validate_namespace
 from aws_embedded_metrics.config import get_config
 from typing import Any, Awaitable, Callable, Dict, Tuple
 import sys
@@ -74,6 +75,7 @@ def reset_dimensions(self, use_default: bool) -> "MetricsLogger":
         return self
 
     def set_namespace(self, namespace: str) -> "MetricsLogger":
+        validate_namespace(namespace)
         self.context.namespace = namespace
         return self
 
diff --git a/aws_embedded_metrics/unit.py b/aws_embedded_metrics/unit.py
index dfd01e9..58f25e2 100644
--- a/aws_embedded_metrics/unit.py
+++ b/aws_embedded_metrics/unit.py
@@ -1,7 +1,17 @@
-from enum import Enum
+from enum import Enum, EnumMeta
 
 
-class Unit(Enum):
+class UnitMeta(EnumMeta):
+    def __contains__(self, item: object) -> bool:
+        try:
+            self(item)
+        except (ValueError, TypeError):
+            return False
+        else:
+            return True
+
+
+class Unit(Enum, metaclass=UnitMeta):
     SECONDS = "Seconds"
     MICROSECONDS = "Microseconds"
     MILLISECONDS = "Milliseconds"
@@ -28,3 +38,4 @@ class Unit(Enum):
     GIGABITS_PER_SECOND = "Gigabits/Second"
     TERABITS_PER_SECOND = "Terabits/Second"
     COUNT_PER_SECOND = "Count/Second"
+    NONE = "None"
diff --git a/aws_embedded_metrics/validator.py b/aws_embedded_metrics/validator.py
new file mode 100644
index 0000000..b9e8395
--- /dev/null
+++ b/aws_embedded_metrics/validator.py
@@ -0,0 +1,102 @@
+# Copyright 2019 Amazon.com, Inc. or its affiliates.
+# Licensed under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import math
+import re
+from typing import Dict, Optional
+from aws_embedded_metrics.unit import Unit
+from aws_embedded_metrics.exceptions import DimensionSetExceededError, InvalidDimensionError, InvalidMetricError, InvalidNamespaceError
+import aws_embedded_metrics.constants as constants
+
+
+def validate_dimension_set(dimension_set: Dict[str, str]) -> None:
+    """
+    Validates a dimension set
+
+        Parameters:
+            dimension_set (Dict[str, str]): The dimension set to validate
+
+        Raises:
+            DimensionSetExceededError: If the dimension set is too large
+            InvalidDimensionError: If a dimension is invalid
+    """
+    if len(dimension_set) > constants.MAX_DIMENSION_SET_SIZE:
+        raise DimensionSetExceededError(
+            f"Maximum number of dimensions per dimension set allowed are {constants.MAX_DIMENSION_SET_SIZE}")
+
+    for name, value in dimension_set.items():
+        if not name or len(name.strip()) == 0:
+            raise InvalidDimensionError("Dimension name must include at least one non-whitespace character")
+
+        if not value or len(value.strip()) == 0:
+            raise InvalidDimensionError("Dimension value must include at least one non-whitespace character")
+
+        if len(name) > constants.MAX_DIMENSION_NAME_LENGTH:
+            raise InvalidDimensionError(f"Dimension name cannot be longer than {constants.MAX_DIMENSION_NAME_LENGTH} characters")
+
+        if len(value) > constants.MAX_DIMENSION_VALUE_LENGTH:
+            raise InvalidDimensionError(f"Dimension value cannot be longer than {constants.MAX_DIMENSION_VALUE_LENGTH} characters")
+
+        if not name.isascii():
+            raise InvalidDimensionError(f"Dimension name contains invalid characters: {name}")
+
+        if not value.isascii():
+            raise InvalidDimensionError(f"Dimension value contains invalid characters: {value}")
+
+        if name.startswith(":"):
+            raise InvalidDimensionError("Dimension name cannot start with ':'")
+
+
+def validate_metric(name: str, value: float, unit: Optional[str]) -> None:
+    """
+    Validates a metric
+
+        Parameters:
+            name (str): The name of the metric
+            value (float): The value of the metric
+            unit (Optional[str]): The unit of the metric
+
+        Raises:
+            InvalidMetricError: If the metric is invalid
+    """
+    if not name or len(name.strip()) == 0:
+        raise InvalidMetricError("Metric name must include at least one non-whitespace character")
+
+    if len(name) > constants.MAX_DIMENSION_NAME_LENGTH:
+        raise InvalidMetricError(f"Metric name cannot be longer than {constants.MAX_DIMENSION_NAME_LENGTH} characters")
+
+    if not math.isfinite(value):
+        raise InvalidMetricError("Metric value must be finite")
+
+    if unit is not None and unit not in Unit:
+        raise InvalidMetricError(f"Metric unit is not valid: {unit}")
+
+
+def validate_namespace(namespace: str) -> None:
+    """
+    Validates a namespace
+
+        Parameters:
+            namespace (str): The namespace to validate
+
+        Raises:
+            InvalidNamespaceError: If the namespace is invalid
+    """
+    if not namespace or len(namespace.strip()) == 0:
+        raise InvalidNamespaceError("Namespace must include at least one non-whitespace character")
+
+    if len(namespace) > constants.MAX_NAMESPACE_LENGTH:
+        raise InvalidNamespaceError(f"Namespace cannot be longer than {constants.MAX_NAMESPACE_LENGTH} characters")
+
+    if not re.match(constants.VALID_NAMESPACE_REGEX, namespace):
+        raise InvalidNamespaceError(f"Namespace contains invalid characters: {namespace}")
diff --git a/tests/logger/test_metrics_context.py b/tests/logger/test_metrics_context.py
index c77e234..f20ed43 100644
--- a/tests/logger/test_metrics_context.py
+++ b/tests/logger/test_metrics_context.py
@@ -1,10 +1,14 @@
+import pytest
+import math
+import random
+from aws_embedded_metrics import constants
+from aws_embedded_metrics.unit import Unit
 from aws_embedded_metrics import config
 from aws_embedded_metrics.logger.metrics_context import MetricsContext
 from aws_embedded_metrics.constants import DEFAULT_NAMESPACE
-from aws_embedded_metrics.exceptions import DimensionSetExceededError
+from aws_embedded_metrics.exceptions import DimensionSetExceededError, InvalidDimensionError, InvalidMetricError
 from importlib import reload
 from faker import Faker
-import pytest
 
 fake = Faker()
 
@@ -228,12 +232,37 @@ def test_get_dimensions_returns_merged_custom_and_default_dimensions():
     assert [expected_dimensions] == actual_dimensions
 
 
+@pytest.mark.parametrize(
+    "name, value",
+    [
+        (None, "value"),
+        ("", "value"),
+        (" ", "value"),
+        ("a" * (constants.MAX_DIMENSION_NAME_LENGTH + 1), "value"),
+        ("ḓɨɱɛɳʂɨøɳ", "value"),
+        (":dim", "value"),
+        ("dim", ""),
+        ("dim", " "),
+        ("dim", "a" * (constants.MAX_DIMENSION_VALUE_LENGTH + 1)),
+        ("dim", "ṽɑɭʊɛ"),
+    ]
+)
+def test_add_invalid_dimensions_raises_exception(name, value):
+    context = MetricsContext()
+
+    with pytest.raises(InvalidDimensionError):
+        context.put_dimensions({name: value})
+
+    with pytest.raises(InvalidDimensionError):
+        context.set_dimensions([{name: value}])
+
+
 def test_put_metric_adds_metrics():
     # arrange
     context = MetricsContext()
     metric_key = fake.word()
     metric_value = fake.random.random()
-    metric_unit = fake.word()
+    metric_unit = random.choice(list(Unit)).value
 
     # act
     context.put_metric(metric_key, metric_value, metric_unit)
@@ -258,6 +287,28 @@ def test_put_metric_uses_none_unit_if_not_provided():
     assert metric.unit == "None"
 
 
+@pytest.mark.parametrize(
+    "name, value, unit",
+    [
+        ("", 1, "None"),
+        (" ", 1, "Seconds"),
+        ("a" * (constants.MAX_METRIC_NAME_LENGTH + 1), 1, "None"),
+        ("metric", float("inf"), "Count"),
+        ("metric", float("-inf"), "Count"),
+        ("metric", float("nan"), "Count"),
+        ("metric", math.inf, "Seconds"),
+        ("metric", -math.inf, "Seconds"),
+        ("metric", math.nan, "Seconds"),
+        ("metric", 1, "Kilometers/Fahrenheit")
+    ]
+)
+def test_put_invalid_metric_raises_exception(name, value, unit):
+    context = MetricsContext()
+
+    with pytest.raises(InvalidMetricError):
+        context.put_metric(name, value, unit)
+
+
 def test_create_copy_with_context_creates_new_instance():
     # arrange
     context = MetricsContext()
@@ -340,10 +391,10 @@ def test_create_copy_with_context_does_not_copy_metrics():
 def test_set_dimensions_overwrites_all_dimensions():
     # arrange
     context = MetricsContext()
-    context.set_default_dimensions({fake.word(): fake.word})
-    context.put_dimensions({fake.word(): fake.word})
+    context.set_default_dimensions({fake.word(): fake.word()})
+    context.put_dimensions({fake.word(): fake.word()})
 
-    expected_dimensions = [{fake.word(): fake.word}]
+    expected_dimensions = [{fake.word(): fake.word()}]
 
     # act
     context.set_dimensions(expected_dimensions)
diff --git a/tests/logger/test_metrics_logger.py b/tests/logger/test_metrics_logger.py
index 641234a..dbcd088 100644
--- a/tests/logger/test_metrics_logger.py
+++ b/tests/logger/test_metrics_logger.py
@@ -2,6 +2,8 @@
 from aws_embedded_metrics.logger import metrics_logger
 from aws_embedded_metrics.sinks import Sink
 from aws_embedded_metrics.environment import Environment
+from aws_embedded_metrics.exceptions import InvalidNamespaceError
+import aws_embedded_metrics.constants as constants
 import pytest
 from faker import Faker
 from asyncio import Future
@@ -353,6 +355,14 @@ async def test_can_set_namespace(mocker):
     assert context.namespace == expected_value
 
 
+@pytest.mark.parametrize("namespace", [None, "", " ", "a" * (constants.MAX_NAMESPACE_LENGTH + 1), "ŋàɱȅƨƥȁƈȅ", "namespace "])
+def test_set_invalid_namespace_throws_exception(namespace, mocker):
+    logger, sink, env = get_logger_and_sink(mocker)
+
+    with pytest.raises(InvalidNamespaceError):
+        logger.set_namespace(namespace)
+
+
 @pytest.mark.asyncio
 async def test_context_is_preserved_across_flushes(mocker):
     # arrange
diff --git a/tests/serializer/test_log_serializer.py b/tests/serializer/test_log_serializer.py
index b6098bc..3114b34 100644
--- a/tests/serializer/test_log_serializer.py
+++ b/tests/serializer/test_log_serializer.py
@@ -94,7 +94,7 @@ def test_serialize_metrics():
 
 def test_serialize_more_than_100_metrics():
     # arrange
-    expected_value = fake.word()
+    expected_value = fake.random.randrange(0, 100)
     expected_batches = 3
     metrics = 295
 
@@ -209,7 +209,7 @@ def test_serialize_with_multiple_metrics():
 
     for index in range(metrics):
         expected_key = f"Metric-{index}"
-        expected_value = fake.word()
+        expected_value = fake.random.randrange(0, 100)
         context.put_metric(expected_key, expected_value)
 
         expected_metric_definition = {"Name": expected_key, "Unit": "None"}
@@ -229,7 +229,7 @@ def test_serialize_with_multiple_metrics():
 def test_serialize_metrics_with_multiple_datapoints():
     # arrange
     expected_key = fake.word()
-    expected_values = [fake.word(), fake.word()]
+    expected_values = [fake.random.randrange(0, 100), fake.random.randrange(0, 100)]
     expected_metric_definition = {"Name": expected_key, "Unit": "None"}
     expected = {**get_empty_payload()}
     expected[expected_key] = expected_values