diff --git a/go/vt/vttablet/tabletserver/debugenv.go b/go/vt/vttablet/tabletserver/debugenv.go
index 50a200ec3ad..87d2a81a424 100644
--- a/go/vt/vttablet/tabletserver/debugenv.go
+++ b/go/vt/vttablet/tabletserver/debugenv.go
@@ -23,6 +23,7 @@ import (
 	"net/http"
 	"strconv"
 	"text/template"
+	"time"
 
 	"vitess.io/vitess/go/acl"
 	"vitess.io/vitess/go/vt/log"
@@ -72,6 +73,15 @@ func debugEnvHandler(tsv *TabletServer, w http.ResponseWriter, r *http.Request)
 			f(ival)
 			msg = fmt.Sprintf("Setting %v to: %v", varname, value)
 		}
+		setDurationVal := func(f func(time.Duration)) {
+			durationVal, err := time.ParseDuration(value)
+			if err != nil {
+				msg = fmt.Sprintf("Failed setting value for %v: %v", varname, err)
+				return
+			}
+			f(durationVal)
+			msg = fmt.Sprintf("Setting %v to: %v", varname, value)
+		}
 		switch varname {
 		case "PoolSize":
 			setIntVal(tsv.SetPoolSize)
@@ -85,6 +95,10 @@ func debugEnvHandler(tsv *TabletServer, w http.ResponseWriter, r *http.Request)
 			setIntVal(tsv.SetMaxResultSize)
 		case "WarnResultSize":
 			setIntVal(tsv.SetWarnResultSize)
+		case "UnhealthyThreshold":
+			setDurationVal(tsv.Config().Healthcheck.UnhealthyThresholdSeconds.Set)
+			setDurationVal(tsv.hs.SetUnhealthyThreshold)
+			setDurationVal(tsv.sm.SetUnhealthyThreshold)
 		case "Consolidator":
 			tsv.SetConsolidatorMode(value)
 			msg = fmt.Sprintf("Setting %v to: %v", varname, value)
@@ -98,12 +112,19 @@ func debugEnvHandler(tsv *TabletServer, w http.ResponseWriter, r *http.Request)
 			Value:   fmt.Sprintf("%v", f()),
 		})
 	}
+	addDurationVar := func(varname string, f func() time.Duration) {
+		vars = append(vars, envValue{
+			VarName: varname,
+			Value:   fmt.Sprintf("%v", f()),
+		})
+	}
 	addIntVar("PoolSize", tsv.PoolSize)
 	addIntVar("StreamPoolSize", tsv.StreamPoolSize)
 	addIntVar("TxPoolSize", tsv.TxPoolSize)
 	addIntVar("QueryCacheCapacity", tsv.QueryPlanCacheCap)
 	addIntVar("MaxResultSize", tsv.MaxResultSize)
 	addIntVar("WarnResultSize", tsv.WarnResultSize)
+	addDurationVar("UnhealthyThreshold", tsv.Config().Healthcheck.UnhealthyThresholdSeconds.Get)
 	vars = append(vars, envValue{
 		VarName: "Consolidator",
 		Value:   tsv.ConsolidatorMode(),
diff --git a/go/vt/vttablet/tabletserver/health_streamer.go b/go/vt/vttablet/tabletserver/health_streamer.go
index b42fcb4f1d6..36e856d3e8e 100644
--- a/go/vt/vttablet/tabletserver/health_streamer.go
+++ b/go/vt/vttablet/tabletserver/health_streamer.go
@@ -28,6 +28,7 @@ import (
 	"github.com/golang/protobuf/proto"
 
 	"vitess.io/vitess/go/history"
+	"vitess.io/vitess/go/sync2"
 	"vitess.io/vitess/go/vt/log"
 	querypb "vitess.io/vitess/go/vt/proto/query"
 	topodatapb "vitess.io/vitess/go/vt/proto/topodata"
@@ -51,7 +52,7 @@ var (
 type healthStreamer struct {
 	stats              *tabletenv.Stats
 	degradedThreshold  time.Duration
-	unhealthyThreshold time.Duration
+	unhealthyThreshold sync2.AtomicDuration
 
 	mu      sync.Mutex
 	ctx     context.Context
@@ -66,7 +67,7 @@ func newHealthStreamer(env tabletenv.Env, alias topodatapb.TabletAlias) *healthS
 	return &healthStreamer{
 		stats:              env.Stats(),
 		degradedThreshold:  env.Config().Healthcheck.DegradedThresholdSeconds.Get(),
-		unhealthyThreshold: env.Config().Healthcheck.UnhealthyThresholdSeconds.Get(),
+		unhealthyThreshold: sync2.NewAtomicDuration(env.Config().Healthcheck.UnhealthyThresholdSeconds.Get()),
 		clients:            make(map[chan *querypb.StreamHealthResponse]struct{}),
 
 		state: &querypb.StreamHealthResponse{
@@ -220,7 +221,7 @@ func (hs *healthStreamer) AppendDetails(details []*kv) []*kv {
 	sbm := time.Duration(hs.state.RealtimeStats.SecondsBehindMaster) * time.Second
 	class := healthyClass
 	switch {
-	case sbm > hs.unhealthyThreshold:
+	case sbm > hs.unhealthyThreshold.Get():
 		class = unhealthyClass
 	case sbm > hs.degradedThreshold:
 		class = unhappyClass
@@ -240,3 +241,17 @@ func (hs *healthStreamer) AppendDetails(details []*kv) []*kv {
 
 	return details
 }
+
+func (hs *healthStreamer) SetUnhealthyThreshold(v time.Duration) {
+	hs.unhealthyThreshold.Set(v)
+	shr := proto.Clone(hs.state).(*querypb.StreamHealthResponse)
+	for ch := range hs.clients {
+		select {
+		case ch <- shr:
+		default:
+			log.Info("Resetting health streamer clients due to unhealthy threshold change")
+			close(ch)
+			delete(hs.clients, ch)
+		}
+	}
+}
diff --git a/go/vt/vttablet/tabletserver/state_manager.go b/go/vt/vttablet/tabletserver/state_manager.go
index c1498e43f44..a18a5ec091d 100644
--- a/go/vt/vttablet/tabletserver/state_manager.go
+++ b/go/vt/vttablet/tabletserver/state_manager.go
@@ -122,7 +122,7 @@ type stateManager struct {
 	checkMySQLThrottler *sync2.Semaphore
 
 	timebombDuration      time.Duration
-	unhealthyThreshold    time.Duration
+	unhealthyThreshold    sync2.AtomicDuration
 	shutdownGracePeriod   time.Duration
 	transitionGracePeriod time.Duration
 }
@@ -187,7 +187,7 @@ func (sm *stateManager) Init(env tabletenv.Env, target querypb.Target) {
 	sm.checkMySQLThrottler = sync2.NewSemaphore(1, 0)
 	sm.timebombDuration = env.Config().OltpReadPool.TimeoutSeconds.Get() * 10
 	sm.hcticks = timer.NewTimer(env.Config().Healthcheck.IntervalSeconds.Get())
-	sm.unhealthyThreshold = env.Config().Healthcheck.UnhealthyThresholdSeconds.Get()
+	sm.unhealthyThreshold = sync2.NewAtomicDuration(env.Config().Healthcheck.UnhealthyThresholdSeconds.Get())
 	sm.shutdownGracePeriod = env.Config().GracePeriods.ShutdownSeconds.Get()
 	sm.transitionGracePeriod = env.Config().GracePeriods.TransitionSeconds.Get()
 }
@@ -640,7 +640,7 @@ func (sm *stateManager) refreshReplHealthLocked() (time.Duration, error) {
 		}
 		sm.replHealthy = false
 	} else {
-		if lag > sm.unhealthyThreshold {
+		if lag > sm.unhealthyThreshold.Get() {
 			if sm.replHealthy {
 				log.Infof("Going unhealthy due to high replication lag: %v", lag)
 			}
@@ -768,3 +768,7 @@ func (sm *stateManager) IsServingString() string {
 	}
 	return "NOT_SERVING"
 }
+
+func (sm *stateManager) SetUnhealthyThreshold(v time.Duration) {
+	sm.unhealthyThreshold.Set(v)
+}