diff --git a/CHANGELOG.md b/CHANGELOG.md
index a6736c4a58e..fb2d15aae45 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,6 +18,9 @@ release.
 
 ### Metrics
 
+- Add normative language to the Metrics API/SDK spec concurrency requirements.
+  ([#4868](https://github.com/open-telemetry/opentelemetry-specification/pull/4868))
+
 ### Logs
 
 - Add optional `Exception` parameter to Emit LogRecord.
diff --git a/specification/metrics/api.md b/specification/metrics/api.md
index 1d91baab7b7..c37fccc944d 100644
--- a/specification/metrics/api.md
+++ b/specification/metrics/api.md
@@ -1342,12 +1342,14 @@ APIs without introducing breaking changes, if possible.
 For languages which support concurrent execution the Metrics APIs provide
 specific guarantees and safeties.
 
-**MeterProvider** - all methods are safe to be called concurrently.
+**MeterProvider** - all methods MUST be documented that implementations need to
+be safe for concurrent use by default.
 
-**Meter** - all methods are safe to be called concurrently.
+**Meter** - all methods MUST be documented that implementations need to be safe
+for concurrent use by default.
 
-**Instrument** - All methods of any Instrument are safe to be called
-concurrently.
+**Instrument** - all methods MUST be documented that implementations need to be
+safe for concurrent use by default.
 
 ## References
 
diff --git a/specification/metrics/sdk.md b/specification/metrics/sdk.md
index c5b27d72f1b..0c3da4b83fc 100644
--- a/specification/metrics/sdk.md
+++ b/specification/metrics/sdk.md
@@ -1847,15 +1847,15 @@ existing methods without introducing breaking changes, if possible.
 For languages which support concurrent execution the Metrics SDKs provide
 specific guarantees and safeties.
 
-**MeterProvider** - Meter creation, `ForceFlush` and `Shutdown` are safe to be
-called concurrently.
+**MeterProvider** - Meter creation, `ForceFlush` and `Shutdown` MUST be safe
+to be called concurrently.
 
-**ExemplarReservoir** - all methods are safe to be called concurrently.
+**ExemplarReservoir** - all methods MUST be safe to be called concurrently.
 
 **MetricReader** - `Collect`, `ForceFlush` (for periodic exporting MetricReader)
-and `Shutdown` are safe to be called concurrently.
+and `Shutdown` MUST be safe to be called concurrently.
 
-**MetricExporter** - `ForceFlush` and `Shutdown` are safe to be called
+**MetricExporter** - `ForceFlush` and `Shutdown` MUST be safe to be called
 concurrently.
 
 ## References