diff --git a/go.mod b/go.mod
index 5aa7f65..b0dbdba 100644
--- a/go.mod
+++ b/go.mod
@@ -4,6 +4,7 @@ go 1.17
 
 require (
 	github.com/cert-manager/cert-manager v1.8.0
+	github.com/prometheus/client_golang v1.12.1
 	github.com/sirupsen/logrus v1.8.1
 	github.com/spf13/cobra v1.4.0
 	github.com/spf13/viper v1.10.0
@@ -61,7 +62,6 @@ require (
 	github.com/peterbourgon/diskv v2.0.1+incompatible // indirect
 	github.com/pkg/errors v0.9.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
-	github.com/prometheus/client_golang v1.12.1 // indirect
 	github.com/prometheus/client_model v0.2.0 // indirect
 	github.com/prometheus/common v0.32.1 // indirect
 	github.com/prometheus/procfs v0.7.3 // indirect
diff --git a/internal/controllers/v1beta1/garbagecollection/garbagecollection.go b/internal/controllers/v1beta1/garbagecollection/garbagecollection.go
index 79b2d82..863df00 100644
--- a/internal/controllers/v1beta1/garbagecollection/garbagecollection.go
+++ b/internal/controllers/v1beta1/garbagecollection/garbagecollection.go
@@ -7,6 +7,7 @@ import (
 
 	certmanagerversionedclient "github.com/cert-manager/cert-manager/pkg/client/clientset/versioned"
 	certmanagerinformers "github.com/cert-manager/cert-manager/pkg/client/informers/externalversions"
+	"github.com/kanopy-platform/gateway-certificate-controller/internal/prometheus"
 	v1beta1labels "github.com/kanopy-platform/gateway-certificate-controller/pkg/v1beta1/labels"
 	networkingv1beta1 "istio.io/client-go/pkg/apis/networking/v1beta1"
 	istioversionedclient "istio.io/client-go/pkg/clientset/versioned"
@@ -28,6 +29,7 @@ type GarbageCollectionController struct {
 	certmanagerClient certmanagerversionedclient.Interface
 	istioClient       istioversionedclient.Interface
 	dryRun            bool
+	managedCerts      map[string]bool
 }
 
 func NewGarbageCollectionController(istioClient istioversionedclient.Interface, certClient certmanagerversionedclient.Interface, opts ...OptionsFunc) *GarbageCollectionController {
@@ -35,6 +37,7 @@ func NewGarbageCollectionController(istioClient istioversionedclient.Interface,
 		name:              "istio-garbage-collection-controller",
 		certmanagerClient: certClient,
 		istioClient:       istioClient,
+		managedCerts:      make(map[string]bool),
 	}
 
 	for _, opt := range opts {
@@ -75,6 +78,8 @@ func (c *GarbageCollectionController) Reconcile(ctx context.Context, request rec
 	log := log.FromContext(ctx)
 	log.V(1).Info("Running Garbage Collection Reconcile", "request", request.String())
 
+	c.managedCerts[request.String()] = true
+
 	certIface := c.certmanagerClient.CertmanagerV1().Certificates(request.Namespace)
 	cert, err := certIface.Get(ctx, request.Name, metav1.GetOptions{})
 	if err != nil {
@@ -109,8 +114,11 @@ func (c *GarbageCollectionController) Reconcile(ctx context.Context, request rec
 				Requeue: true,
 			}, err
 		}
+
+		delete(c.managedCerts, request.String())
 	}
 
+	prometheus.UpdateManagedCertificatesCount(len(c.managedCerts))
 	return reconcile.Result{}, nil
 }
 
diff --git a/internal/controllers/v1beta1/garbagecollection/garbagecollection_test.go b/internal/controllers/v1beta1/garbagecollection/garbagecollection_test.go
index 913a0fb..9b4a492 100644
--- a/internal/controllers/v1beta1/garbagecollection/garbagecollection_test.go
+++ b/internal/controllers/v1beta1/garbagecollection/garbagecollection_test.go
@@ -29,6 +29,7 @@ func TestNewGarbageCollectionController(t *testing.T) {
 		certmanagerClient: certmanagerClient,
 		istioClient:       istioClient,
 		dryRun:            dryRun,
+		managedCerts:      map[string]bool{},
 	}
 
 	gc := NewGarbageCollectionController(istioClient, certmanagerClient, WithDryRun(dryRun))
diff --git a/internal/prometheus/prometheus.go b/internal/prometheus/prometheus.go
new file mode 100644
index 0000000..8ab4110
--- /dev/null
+++ b/internal/prometheus/prometheus.go
@@ -0,0 +1,30 @@
+package prometheus
+
+import (
+	"net/http"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"sigs.k8s.io/controller-runtime/pkg/metrics"
+)
+
+var (
+	managedCertificatesCount = prometheus.NewGauge(prometheus.GaugeOpts{
+		Name: "managed_certificates_count",
+		Help: "Count of controller managed certificates",
+	})
+)
+
+func init() {
+	metrics.Registry.MustRegister(managedCertificatesCount)
+}
+
+func Handler() http.Handler {
+	return promhttp.InstrumentMetricHandler(
+		metrics.Registry, promhttp.HandlerFor(metrics.Registry, promhttp.HandlerOpts{}),
+	)
+}
+
+func UpdateManagedCertificatesCount(count int) {
+	managedCertificatesCount.Set(float64(count))
+}
diff --git a/internal/prometheus/prometheus_test.go b/internal/prometheus/prometheus_test.go
new file mode 100644
index 0000000..d999988
--- /dev/null
+++ b/internal/prometheus/prometheus_test.go
@@ -0,0 +1,22 @@
+package prometheus
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMetrics(t *testing.T) {
+	t.Parallel()
+
+	req, err := http.NewRequest("GET", "/", nil)
+	assert.NoError(t, err)
+
+	rr := httptest.NewRecorder()
+
+	Handler().ServeHTTP(rr, req)
+	body := rr.Body.String()
+	assert.Contains(t, body, `managed_certificates_count`)
+}