diff --git a/src/hss/hss-context.c b/src/hss/hss-context.c
index fede57703..f80cded8d 100644
--- a/src/hss/hss-context.c
+++ b/src/hss/hss-context.c
@@ -337,6 +337,8 @@ int hss_context_parse_config(void)
 #else
                     self.use_mongodb_change_stream = false;
 #endif
+                } else if (!strcmp(hss_key, "metrics")) {
+                    /* handle config in metrics library */
                 } else
                     ogs_warn("unknown key `%s`", hss_key);
             }
@@ -519,6 +521,7 @@ static hss_imsi_t *imsi_add(char *id)
     ogs_hash_set(self.imsi_hash, imsi->id, strlen(imsi->id), imsi);
 
     ogs_list_add(&self.imsi_list, imsi);
+    hss_metrics_inst_global_inc(HSS_METR_GLOB_GAUGE_IMSI);
 
     return imsi;
 }
@@ -528,6 +531,7 @@ static void imsi_remove(hss_imsi_t *imsi)
     ogs_assert(imsi);
 
     ogs_list_remove(&self.imsi_list, imsi);
+    hss_metrics_inst_global_dec(HSS_METR_GLOB_GAUGE_IMSI);
 
     ogs_assert(imsi->id);
     ogs_hash_set(self.imsi_hash, imsi->id, strlen(imsi->id), NULL);
@@ -569,6 +573,7 @@ static hss_impi_t *impi_add(char *id)
     ogs_hash_set(self.impi_hash, impi->id, strlen(impi->id), impi);
 
     ogs_list_add(&self.impi_list, impi);
+    hss_metrics_inst_global_inc(HSS_METR_GLOB_GAUGE_IMPI);
 
     return impi;
 }
@@ -578,6 +583,7 @@ static void impi_remove(hss_impi_t *impi)
     ogs_assert(impi);
 
     ogs_list_remove(&self.impi_list, impi);
+    hss_metrics_inst_global_dec(HSS_METR_GLOB_GAUGE_IMPI);
 
     impu_remove_all(impi);
 
@@ -633,7 +639,9 @@ static hss_impu_t *impu_add(hss_impi_t *impi, char *id)
     ogs_hash_set(self.impu_hash, impu->id, strlen(impu->id), impu);
 
     impu->impi = impi;
+
     ogs_list_add(&impi->impu_list, impu);
+    hss_metrics_inst_global_inc(HSS_METR_GLOB_GAUGE_IMPU);
 
     return impu;
 }
@@ -647,6 +655,7 @@ static void impu_remove(hss_impu_t *impu)
     ogs_assert(impi);
 
     ogs_list_remove(&impi->impu_list, impu);
+    hss_metrics_inst_global_dec(HSS_METR_GLOB_GAUGE_IMPU);
 
     ogs_assert(impu->id);
     ogs_hash_set(self.impu_hash, impu->id, strlen(impu->id), NULL);
diff --git a/src/hss/hss-context.h b/src/hss/hss-context.h
index b5afd46b4..1fe0ddc70 100644
--- a/src/hss/hss-context.h
+++ b/src/hss/hss-context.h
@@ -25,6 +25,7 @@
 #include "ogs-diameter-swx.h"
 #include "ogs-dbi.h"
 #include "ogs-app.h"
+#include "metrics.h"
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/src/hss/hss-init.c b/src/hss/hss-init.c
index 305d9ef22..7d8139e83 100644
--- a/src/hss/hss-init.c
+++ b/src/hss/hss-init.c
@@ -20,6 +20,7 @@
 #include "hss-context.h"
 #include "hss-fd-path.h"
 #include "hss-sm.h"
+#include "metrics.h"
 
 
 static ogs_thread_t *thread;
@@ -35,9 +36,14 @@ int hss_initialize(void)
     rv = ogs_app_parse_local_conf(APP_NAME);
     if (rv != OGS_OK) return rv;
 
+    hss_metrics_init();
+
     hss_context_init();
     hss_event_init();
 
+    rv = ogs_metrics_context_parse_config(APP_NAME);
+    if (rv != OGS_OK) return rv;
+
     rv = hss_context_parse_config();
     if (rv != OGS_OK) return rv;
 
@@ -45,6 +51,8 @@ int hss_initialize(void)
             ogs_app()->logger.domain, ogs_app()->logger.level);
     if (rv != OGS_OK) return rv;
 
+    ogs_metrics_context_open(ogs_metrics_self());
+
     rv = ogs_dbi_init(ogs_app()->db_uri);
     if (rv != OGS_OK) return rv;
 
@@ -65,12 +73,14 @@ void hss_terminate(void)
 
     hss_event_term();
     ogs_thread_destroy(thread);
+    ogs_metrics_context_close(ogs_metrics_self());
 
     hss_fd_final();
 
     ogs_dbi_final();
     hss_context_final();
     hss_event_final();
+    hss_metrics_final();
 
     return;
 }
diff --git a/src/hss/meson.build b/src/hss/meson.build
index 83130a444..378139eea 100644
--- a/src/hss/meson.build
+++ b/src/hss/meson.build
@@ -22,6 +22,7 @@ libhss_sources = files('''
     hss-event.h
     hss-timer.h
     hss-sm.h
+    metrics.h
 
     hss-init.c
     hss-context.c
@@ -34,11 +35,14 @@ libhss_sources = files('''
     hss-swx-path.c
 
     hss-fd-path.c
+
+    metrics.c
 '''.split())
 
 libhss = static_library('hss',
     sources : libhss_sources,
-    dependencies : [libapp_dep,
+    dependencies : [libmetrics_dep,
+                    libapp_dep,
                     libcrypt_dep,
                     libdbi_dep,
                     libdiameter_s6a_dep,
@@ -48,7 +52,8 @@ libhss = static_library('hss',
 
 libhss_dep = declare_dependency(
     link_with : libhss,
-    dependencies : [libapp_dep,
+    dependencies : [libmetrics_dep,
+                    libapp_dep,
                     libcrypt_dep,
                     libdbi_dep,
                     libdiameter_s6a_dep,
diff --git a/src/hss/metrics.c b/src/hss/metrics.c
new file mode 100644
index 000000000..b14426095
--- /dev/null
+++ b/src/hss/metrics.c
@@ -0,0 +1,93 @@
+#include "ogs-app.h"
+#include "hss-context.h"
+
+#include "metrics.h"
+
+typedef struct hss_metrics_spec_def_s {
+    unsigned int type;
+    const char *name;
+    const char *description;
+    int initial_val;
+    unsigned int num_labels;
+    const char **labels;
+} hss_metrics_spec_def_t;
+
+/* Helper generic functions: */
+static int hss_metrics_init_inst(ogs_metrics_inst_t **inst, ogs_metrics_spec_t **specs,
+        unsigned int len, unsigned int num_labels, const char **labels)
+{
+    unsigned int i;
+    for (i = 0; i < len; i++)
+        inst[i] = ogs_metrics_inst_new(specs[i], num_labels, labels);
+    return OGS_OK;
+}
+
+static int hss_metrics_free_inst(ogs_metrics_inst_t **inst,
+        unsigned int len)
+{
+    unsigned int i;
+    for (i = 0; i < len; i++)
+        ogs_metrics_inst_free(inst[i]);
+    memset(inst, 0, sizeof(inst[0]) * len);
+    return OGS_OK;
+}
+
+static int hss_metrics_init_spec(ogs_metrics_context_t *ctx,
+        ogs_metrics_spec_t **dst, hss_metrics_spec_def_t *src, unsigned int len)
+{
+    unsigned int i;
+    for (i = 0; i < len; i++) {
+        dst[i] = ogs_metrics_spec_new(ctx, src[i].type,
+                src[i].name, src[i].description,
+                src[i].initial_val, src[i].num_labels, src[i].labels,
+                NULL);
+    }
+    return OGS_OK;
+}
+
+/* GLOBAL */
+ogs_metrics_spec_t *hss_metrics_spec_global[_HSS_METR_GLOB_MAX];
+ogs_metrics_inst_t *hss_metrics_inst_global[_HSS_METR_GLOB_MAX];
+hss_metrics_spec_def_t hss_metrics_spec_def_global[_HSS_METR_GLOB_MAX] = {
+/* Global Gauges: */
+[HSS_METR_GLOB_GAUGE_IMSI] = {
+    .type = OGS_METRICS_METRIC_TYPE_GAUGE,
+    .name = "hss_imsi",
+    .description = "Number of IMSIs attached to HSS",
+},
+[HSS_METR_GLOB_GAUGE_IMPI] = {
+    .type = OGS_METRICS_METRIC_TYPE_GAUGE,
+    .name = "hss_impi",
+    .description = "Number of IMPIs attached to HSS",
+},
+[HSS_METR_GLOB_GAUGE_IMPU] = {
+    .type = OGS_METRICS_METRIC_TYPE_GAUGE,
+    .name = "hss_impu",
+    .description = "Number of IMPUs attached to HSS",
+},
+};
+int hss_metrics_init_inst_global(void)
+{
+    return hss_metrics_init_inst(hss_metrics_inst_global, hss_metrics_spec_global,
+                _HSS_METR_GLOB_MAX, 0, NULL);
+}
+int hss_metrics_free_inst_global(void)
+{
+    return hss_metrics_free_inst(hss_metrics_inst_global, _HSS_METR_GLOB_MAX);
+}
+
+void hss_metrics_init(void)
+{
+    ogs_metrics_context_t *ctx = ogs_metrics_self();
+    ogs_metrics_context_init();
+
+    hss_metrics_init_spec(ctx, hss_metrics_spec_global, hss_metrics_spec_def_global,
+            _HSS_METR_GLOB_MAX);
+
+    hss_metrics_init_inst_global();
+}
+
+void hss_metrics_final(void)
+{
+    ogs_metrics_context_final();
+}
diff --git a/src/hss/metrics.h b/src/hss/metrics.h
new file mode 100644
index 000000000..c0b36a33f
--- /dev/null
+++ b/src/hss/metrics.h
@@ -0,0 +1,38 @@
+#ifndef HSS_METRICS_H
+#define HSS_METRICS_H
+
+#include "ogs-metrics.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* GLOBAL */
+typedef enum hss_metric_type_global_s {
+    HSS_METR_GLOB_GAUGE_IMSI,
+    HSS_METR_GLOB_GAUGE_IMPI,
+    HSS_METR_GLOB_GAUGE_IMPU,
+    _HSS_METR_GLOB_MAX,
+} hss_metric_type_global_t;
+extern ogs_metrics_inst_t *hss_metrics_inst_global[_HSS_METR_GLOB_MAX];
+
+int hss_metrics_init_inst_global(void);
+int hss_metrics_free_inst_global(void);
+
+static inline void hss_metrics_inst_global_set(hss_metric_type_global_t t, int val)
+{ ogs_metrics_inst_set(hss_metrics_inst_global[t], val); }
+static inline void hss_metrics_inst_global_add(hss_metric_type_global_t t, int val)
+{ ogs_metrics_inst_add(hss_metrics_inst_global[t], val); }
+static inline void hss_metrics_inst_global_inc(hss_metric_type_global_t t)
+{ ogs_metrics_inst_inc(hss_metrics_inst_global[t]); }
+static inline void hss_metrics_inst_global_dec(hss_metric_type_global_t t)
+{ ogs_metrics_inst_dec(hss_metrics_inst_global[t]); }
+
+void hss_metrics_init(void);
+void hss_metrics_final(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* HSS_METRICS_H */