diff --git a/discovery/aws/ec2.go b/discovery/aws/ec2.go
index d2ad9736a..0bcfd0547 100644
--- a/discovery/aws/ec2.go
+++ b/discovery/aws/ec2.go
@@ -194,24 +194,16 @@ func (d *EC2Discovery) ec2Client(ctx context.Context) (*ec2.EC2, error) {
 	return d.ec2, nil
 }
 
-func (d *EC2Discovery) azID(ctx context.Context, az string) (string, error) {
-	if azID, ok := d.azToAZID[az]; ok {
-		return azID, nil
-	}
-
+func (d *EC2Discovery) refreshAZIDs(ctx context.Context) error {
 	azs, err := d.ec2.DescribeAvailabilityZonesWithContext(ctx, &ec2.DescribeAvailabilityZonesInput{})
 	if err != nil {
-		return "", errors.Wrap(err, "could not describe availability zones")
+		return err
 	}
 	d.azToAZID = make(map[string]string, len(azs.AvailabilityZones))
 	for _, az := range azs.AvailabilityZones {
 		d.azToAZID[*az.ZoneName] = *az.ZoneId
 	}
-
-	if azID, ok := d.azToAZID[az]; ok {
-		return azID, nil
-	}
-	return "", fmt.Errorf("no availability zone ID mapping found for %s", az)
+	return nil
 }
 
 func (d *EC2Discovery) refresh(ctx context.Context) ([]*targetgroup.Group, error) {
@@ -232,21 +224,23 @@ func (d *EC2Discovery) refresh(ctx context.Context) ([]*targetgroup.Group, error
 		})
 	}
 
-	input := &ec2.DescribeInstancesInput{Filters: filters}
+	// Only refresh the AZ ID map if we have never been able to build one.
+	// Prometheus requires a reload if AWS adds a new AZ to the region.
+	if d.azToAZID == nil {
+		if err := d.refreshAZIDs(ctx); err != nil {
+			level.Debug(d.logger).Log(
+				"msg", "Unable to describe availability zones",
+				"err", err)
+		}
+	}
 
+	input := &ec2.DescribeInstancesInput{Filters: filters}
 	if err := ec2Client.DescribeInstancesPagesWithContext(ctx, input, func(p *ec2.DescribeInstancesOutput, lastPage bool) bool {
 		for _, r := range p.Reservations {
 			for _, inst := range r.Instances {
 				if inst.PrivateIpAddress == nil {
 					continue
 				}
-				azID, err := d.azID(ctx, *inst.Placement.AvailabilityZone)
-				if err != nil {
-					level.Warn(d.logger).Log(
-						"msg", "Unable to determine availability zone ID",
-						"az", *inst.Placement.AvailabilityZone,
-						"err", err)
-				}
 
 				labels := model.LabelSet{
 					ec2LabelInstanceID: model.LabelValue(*inst.InstanceId),
@@ -271,9 +265,14 @@ func (d *EC2Discovery) refresh(ctx context.Context) ([]*targetgroup.Group, error
 					labels[ec2LabelPublicIP] = model.LabelValue(*inst.PublicIpAddress)
 					labels[ec2LabelPublicDNS] = model.LabelValue(*inst.PublicDnsName)
 				}
-
 				labels[ec2LabelAMI] = model.LabelValue(*inst.ImageId)
 				labels[ec2LabelAZ] = model.LabelValue(*inst.Placement.AvailabilityZone)
+				azID, ok := d.azToAZID[*inst.Placement.AvailabilityZone]
+				if !ok && d.azToAZID != nil {
+					level.Debug(d.logger).Log(
+						"msg", "Availability zone ID not found",
+						"az", *inst.Placement.AvailabilityZone)
+				}
 				labels[ec2LabelAZID] = model.LabelValue(azID)
 				labels[ec2LabelInstanceState] = model.LabelValue(*inst.State.Name)
 				labels[ec2LabelInstanceType] = model.LabelValue(*inst.InstanceType)
diff --git a/docs/configuration/configuration.md b/docs/configuration/configuration.md
index e48ba6a0b..d5dd52d05 100644
--- a/docs/configuration/configuration.md
+++ b/docs/configuration/configuration.md
@@ -898,7 +898,7 @@ The following meta labels are available on targets during [relabeling](#relabel_
 * `__meta_ec2_ami`: the EC2 Amazon Machine Image
 * `__meta_ec2_architecture`: the architecture of the instance
 * `__meta_ec2_availability_zone`: the availability zone in which the instance is running
-* `__meta_ec2_availability_zone_id`: the [availability zone ID](https://docs.aws.amazon.com/ram/latest/userguide/working-with-az-ids.html) in which the instance is running
+* `__meta_ec2_availability_zone_id`: the [availability zone ID](https://docs.aws.amazon.com/ram/latest/userguide/working-with-az-ids.html) in which the instance is running (requires `ec2:DescribeAvailabilityZones`)
 * `__meta_ec2_instance_id`: the EC2 instance ID
 * `__meta_ec2_instance_lifecycle`: the lifecycle of the EC2 instance, set only for 'spot' or 'scheduled' instances, absent otherwise
 * `__meta_ec2_instance_state`: the state of the EC2 instance