istio.io/content/help/faq/security/k8s-health-checks.md

title	weight
How can I use Kubernetes liveness and readiness for service health check with Istio Auth enabled?	40

If Istio Auth is enabled, http and tcp health check from kubelet will not work since they do not have Istio Auth issued certs. A workaround is to use a liveness command for health check, e.g., one can install curl in the service pod and curl itself within the pod. The Istio team is actively working on a solution.

An example of readinessProbe:

livenessProbe:
exec:
  command:
  - curl
  - -f
  - http://localhost:8080/healthz # Replace port and URI by your actual health check
initialDelaySeconds: 10
periodSeconds: 5