---
title: Alert on No Change in value
description: >-
  Configure metric monitors to trigger alerts when values remain unchanged over
  time using diff() and abs() functions.
breadcrumbs: Docs > Monitors > Monitor Guides > Alert on No Change in value
---

# Alert on No Change in value

A simple way to trigger an alert when a metric value does not change over a set period of time is to start by using the `diff()` function on your query. This will produce the delta values from consecutive data points.

- `diff(avg:system.mem.free{*})`

Next, apply the abs() function to take the absolute value of these deltas.

- `abs(diff(avg:system.mem.free{*}))`

These functions can be applied to your query in the UI.

{% image
   source="https://docs.dd-static.net/images/monitors/guide/alert_value_difference.4ffb4e05454df0db8afb5b1449af123a.png?auto=format&fit=max&w=850 1x, https://docs.dd-static.net/images/monitors/guide/alert_value_difference.4ffb4e05454df0db8afb5b1449af123a.png?auto=format&fit=max&w=850&dpr=2 2x"
   alt="Apply diff function through Sigma icon > Rate > Value difference" /%}

Alternatively, your complex query can be manually entered in the 'edit monitor' UI, via the Source tab (or applied programmatically via the [API](https://docs.datadoghq.com/api.md)). See image below.

For [alert conditions](https://docs.datadoghq.com/monitors/configuration.md) in the metric monitor itself, configure as follows:

- Select threshold alert
- Set the "Trigger when the metric is…" dropdown selector to **below** or **equal to**
- Set the "Alert Threshold" field to 0 (zero)

This configuration will trigger an alert event when no change in value has been registered over the selected timeframe.

Other [alert conditions/options](https://docs.datadoghq.com/monitors/configuration.md) can be set to preference. Your monitor's UI configuration should end up looking something like this:

{% image
   source="https://docs.dd-static.net/images/monitors/faq/zero_alert.e28701f355ec6b913199a71f70ef1f3f.png?auto=format&fit=max&w=850 1x, https://docs.dd-static.net/images/monitors/faq/zero_alert.e28701f355ec6b913199a71f70ef1f3f.png?auto=format&fit=max&w=850&dpr=2 2x"
   alt="zero_alert" /%}

- [Learn how to create a monitor](https://docs.datadoghq.com/monitors.md)
- [Configure your monitor notifications](https://docs.datadoghq.com/monitors/notify.md)