diff --git a/pageserver/src/metrics.rs b/pageserver/src/metrics.rs
index fa8cd504d0..75ce77f062 100644
--- a/pageserver/src/metrics.rs
+++ b/pageserver/src/metrics.rs
@@ -683,6 +683,15 @@ pub static LAYER_GET_VALUE_RECONSTRUCT_DATA_SPAWN_BLOCKING_STARTED_COUNT: Lazy<I
         .expect("failed to define a metric")
     });
 
+pub static LAYER_GET_VALUE_RECONSTRUCT_DATA_SPAWN_BLOCKING_ACTIVE_GAUGE: Lazy<IntGauge> =
+    Lazy::new(|| {
+        register_int_gauge!(
+            "pageserver_layer_get_value_reconstruct_data_spawn_blocking_active_gauge",
+            "Number of spawn_blocking calls active in Layer::get_value_reconstruct_data"
+        )
+        .expect("failed to define a metric")
+    });
+
 pub static LAYER_GET_VALUE_RECONSTRUCT_DATA_SPAWN_BLOCKING_QUEUE_DELAY: Lazy<Histogram> = Lazy::new(
     || {
         register_histogram!(
diff --git a/pageserver/src/tenant/storage_layer.rs b/pageserver/src/tenant/storage_layer.rs
index 39fd4aae75..e3f517d6c4 100644
--- a/pageserver/src/tenant/storage_layer.rs
+++ b/pageserver/src/tenant/storage_layer.rs
@@ -413,14 +413,17 @@ pub trait Layer: std::fmt::Debug + Send + Sync + 'static {
             ))
         } else {
             crate::metrics::LAYER_GET_VALUE_RECONSTRUCT_DATA_SPAWN_BLOCKING_STARTED_COUNT.inc();
-            tokio::task::spawn_blocking(move || {
+            crate::metrics::LAYER_GET_VALUE_RECONSTRUCT_DATA_SPAWN_BLOCKING_ACTIVE_GAUGE.inc();
+            let res = tokio::task::spawn_blocking(move || {
                 crate::metrics::LAYER_GET_VALUE_RECONSTRUCT_DATA_SPAWN_BLOCKING_QUEUE_DELAY
                     .observe(start.elapsed().as_secs_f64());
                 let _enter = span.enter();
                 self.get_value_reconstruct_data_blocking(key, lsn_range, reconstruct_data, ctx)
             })
             .await
-            .context("spawn_blocking")
+            .context("spawn_blocking");
+            crate::metrics::LAYER_GET_VALUE_RECONSTRUCT_DATA_SPAWN_BLOCKING_ACTIVE_GAUGE.dec();
+            res
         };
         let histo = match &res {
             Ok(Ok(_)) => &crate::metrics::LAYER_GET_VALUE_RECONSTRUCT_DATA_COMPLETION_TIME_OK,