diff --git a/composer.json b/composer.json
index 838cede..87f762d 100644
--- a/composer.json
+++ b/composer.json
@@ -16,7 +16,7 @@
         "wp-cli/checksum-command": "^2 || ^3",
         "wp-cli/core-command": "^2 || ^3",
         "wp-cli/cron-command": "^2 || ^3",
-        "wp-cli/entity-command": "^2 || ^3",
+        "wp-cli/entity-command": "^2.8.12 || ^3",
         "wp-cli/extension-command": "^2 || ^3",
         "wp-cli/language-command": "^2 || ^3",
         "wp-cli/wp-cli": "^3.0"
diff --git a/doctor.yml b/doctor.yml
index bf8fbf9..cddcad3 100644
--- a/doctor.yml
+++ b/doctor.yml
@@ -1,6 +1,8 @@
 # Default check configuration for `wp doctor`
 autoload-options-size:
   check: Autoload_Options_Size
+transients-size:
+  check: Transients_Size
 constant-savequeries-falsy:
   check: Constant_Definition
   options:
diff --git a/features/check-autoload-options-size.feature b/features/check-autoload-options-size.feature
index 1630fb6..500a506 100644
--- a/features/check-autoload-options-size.feature
+++ b/features/check-autoload-options-size.feature
@@ -19,7 +19,7 @@ Feature: Check the size of autoloaded options
     When I run `wp doctor check autoload-options-size --fields=message`
     Then STDOUT should contain:
       """
-      is less than threshold (900kb)
+      does not exceed threshold (900kb)
       """
 
   @less-than-wp-6.5
@@ -59,5 +59,5 @@ Feature: Check the size of autoloaded options
     When I run `wp doctor check autoload-options-size --fields=message --config=custom.yml`
     Then STDOUT should contain:
       """
-      is less than threshold (800kb)
+      does not exceed threshold (800kb)
       """
diff --git a/features/check-transients-size.feature b/features/check-transients-size.feature
new file mode 100644
index 0000000..46daac2
--- /dev/null
+++ b/features/check-transients-size.feature
@@ -0,0 +1,156 @@
+Feature: Check the size of autoloaded transients
+
+  Scenario: Verify check description
+    Given an empty directory
+
+    When I run `wp doctor list --fields=name,description`
+    Then STDOUT should be a table containing rows:
+      | name            | description                                                                      |
+      | transients-size | Warns when autoloaded transients size exceeds threshold of 900 kb.               |
+
+  Scenario: Autoloaded transients are less than 900 kb
+    Given a WP install
+
+    When I run `wp doctor check transients-size --fields=name,status`
+    Then STDOUT should be a table containing rows:
+      | name            | status  |
+      | transients-size | success |
+
+    When I run `wp doctor check transients-size --fields=message`
+    Then STDOUT should contain:
+      """
+      does not exceed threshold (900kb)
+      """
+
+  Scenario: Autoloaded transients equal 900 kb
+    Given a WP install
+    And a wp-content/mu-plugins/exact-threshold-transients.php file:
+      """
+      <?php
+      add_action(
+        'wp_loaded',
+        static function () {
+          global $wpdb;
+
+          $option_names = $wpdb->get_col( "SELECT option_name FROM {$wpdb->options}" );
+          foreach ( $option_names as $option_name ) {
+            if (
+              0 === strpos( $option_name, '_transient_' )
+              || 0 === strpos( $option_name, '_site_transient_' )
+            ) {
+              delete_option( $option_name );
+            }
+          }
+
+          add_option( '_transient_doctor_exact_threshold', str_repeat( '9', 900 * 1024 ), '', true );
+        },
+        PHP_INT_MAX
+      );
+      """
+
+    When I run `wp option list --transients --autoload=on --format=total_bytes`
+    Then STDOUT should be:
+      """
+      921600
+      """
+
+    When I run `wp doctor check transients-size --fields=name,status`
+    Then STDOUT should be a table containing rows:
+      | name            | status  |
+      | transients-size | success |
+
+    When I run `wp doctor check transients-size --fields=message`
+    Then STDOUT should contain:
+      """
+      Autoloaded transients size (900kb) does not exceed threshold (900kb).
+      """
+
+  Scenario: Autoloaded transients are greater than 900 kb
+    Given a WP install
+    And a create-large-transients.php file:
+      """
+      <?php
+      $value = str_repeat( '9', 15000 );
+      for ( $i = 0; $i < 75; $i++ ) {
+        add_option( '_transient_doctor_big_' . $i, $value, '', true );
+      }
+      """
+    And I run `wp eval-file create-large-transients.php`
+
+    When I run `wp doctor check transients-size --fields=name,status`
+    Then STDOUT should be a table containing rows:
+      | name            | status  |
+      | transients-size | warning |
+
+    When I run `wp doctor check transients-size --fields=message`
+    Then STDOUT should contain:
+      """
+      exceeds threshold (900kb)
+      """
+
+  Scenario: Autoloaded options and expiring transients are ignored
+    Given a WP install
+    And a create-large-nonmatching-data.php file:
+      """
+      <?php
+      $value = str_repeat( '9', 15000 );
+      for ( $i = 0; $i < 75; $i++ ) {
+        update_option( 'doctor_big_option_' . $i, $value, true );
+        add_option( '_transient_doctor_expiring_big_' . $i, $value, '', false );
+        add_option( '_transient_timeout_doctor_expiring_big_' . $i, time() + HOUR_IN_SECONDS, '', false );
+      }
+      """
+    And I run `wp eval-file create-large-nonmatching-data.php`
+
+    When I run `wp doctor check transients-size --fields=name,status`
+    Then STDOUT should be a table containing rows:
+      | name            | status  |
+      | transients-size | success |
+
+  Scenario: Custom configuration
+    Given a WP install
+    And a custom.yml file:
+      """
+      transients-size:
+        class: WP_CLI\Doctor\Check\Transients_Size
+        options:
+          threshold_kb: 800
+      """
+
+    When I run `wp doctor check transients-size --fields=message --config=custom.yml`
+    Then STDOUT should contain:
+      """
+      does not exceed threshold (800kb)
+      """
+
+  Scenario: Zero threshold is formatted safely
+    Given a WP install
+    And a custom.yml file:
+      """
+      transients-size:
+        class: WP_CLI\Doctor\Check\Transients_Size
+        options:
+          threshold_kb: 0
+      """
+
+    When I run `wp doctor check transients-size --fields=message --config=custom.yml`
+    Then STDOUT should contain:
+      """
+      threshold (0)
+      """
+
+  Scenario: Very large thresholds are formatted safely
+    Given a WP install
+    And a custom.yml file:
+      """
+      transients-size:
+        class: WP_CLI\Doctor\Check\Transients_Size
+        options:
+          threshold_kb: 1099511627776
+      """
+
+    When I run `wp doctor check transients-size --fields=message --config=custom.yml`
+    Then STDOUT should contain:
+      """
+      does not exceed threshold (1024t)
+      """
diff --git a/features/check.feature b/features/check.feature
index 51b1a14..9c42bd2 100644
--- a/features/check.feature
+++ b/features/check.feature
@@ -160,6 +160,7 @@ Feature: Basic check usage
     Then STDOUT should be a table containing rows:
       | name                  |
       | autoload-options-size |
+      | transients-size       |
       | core-update           |
       | core-verify-checksums |
       | plugin-deactivated    |
diff --git a/src/Check.php b/src/Check.php
index c86b31b..ee0ff91 100644
--- a/src/Check.php
+++ b/src/Check.php
@@ -87,6 +87,24 @@ protected function set_message( $message ) {
 		$this->_message = $message;
 	}
 
+	/**
+	 * Format a byte count for check result messages.
+	 *
+	 * @param int|float $size Size in bytes.
+	 * @param int       $precision Precision.
+	 * @return string
+	 */
+	protected static function format_bytes( $size, $precision = 2 ) {
+		if ( 0 >= $size ) {
+			return '0';
+		}
+
+		$suffixes = array( '', 'kb', 'mb', 'g', 't' );
+		$base     = min( (int) floor( log( $size, 1024 ) ), count( $suffixes ) - 1 );
+
+		return round( $size / pow( 1024, $base ), $precision ) . $suffixes[ $base ];
+	}
+
 	/**
 	 * Run the check.
 	 *
diff --git a/src/Check/Autoload_Options_Size.php b/src/Check/Autoload_Options_Size.php
index 8752410..4ff3ffa 100644
--- a/src/Check/Autoload_Options_Size.php
+++ b/src/Check/Autoload_Options_Size.php
@@ -39,18 +39,7 @@ public function run() {
 			$this->set_message( "Autoloaded options size ({$human_total}) exceeds threshold ({$human_threshold})" );
 		} else {
 			$this->set_status( 'success' );
-			$this->set_message( "Autoloaded options size ({$human_total}) is less than threshold ({$human_threshold})." );
+			$this->set_message( "Autoloaded options size ({$human_total}) does not exceed threshold ({$human_threshold})." );
 		}
 	}
-
-	/**
-	 * @param int|float $size Size in bytes.
-	 * @param int       $precision Precision.
-	 * @return string
-	 */
-	private static function format_bytes( $size, $precision = 2 ) {
-		$base     = log( $size, 1024 );
-		$suffixes = array( '', 'kb', 'mb', 'g', 't' );
-		return round( pow( 1024, $base - floor( $base ) ), $precision ) . $suffixes[ (int) floor( $base ) ];
-	}
 }
diff --git a/src/Check/Transients_Size.php b/src/Check/Transients_Size.php
new file mode 100644
index 0000000..69de176
--- /dev/null
+++ b/src/Check/Transients_Size.php
@@ -0,0 +1,46 @@
+<?php
+
+namespace WP_CLI\Doctor\Check;
+
+use WP_CLI;
+use WP_CLI\Doctor\Check;
+
+/**
+ * Warns when autoloaded transients size exceeds threshold of %threshold_kb% kb.
+ */
+class Transients_Size extends Check {
+
+	/**
+	 * Threshold in kilobytes.
+	 *
+	 * @var integer
+	 */
+	protected $threshold_kb = 900;
+
+	/**
+	 * @return void
+	 */
+	public function run() {
+		ob_start();
+		WP_CLI::run_command(
+			array( 'option', 'list' ),
+			array(
+				'transients' => true,
+				'autoload'   => 'on',
+				'format'     => 'total_bytes',
+			)
+		);
+		$total_bytes = (int) ob_get_clean();
+
+		$threshold_bytes = $this->threshold_kb * 1024;
+		$human_threshold = self::format_bytes( $threshold_bytes );
+		$human_total     = self::format_bytes( $total_bytes );
+		if ( $threshold_bytes < $total_bytes ) {
+			$this->set_status( 'warning' );
+			$this->set_message( "Autoloaded transients size ({$human_total}) exceeds threshold ({$human_threshold})" );
+		} else {
+			$this->set_status( 'success' );
+			$this->set_message( "Autoloaded transients size ({$human_total}) does not exceed threshold ({$human_threshold})." );
+		}
+	}
+}
diff --git a/src/Command.php b/src/Command.php
index 3dd5753..da86f85 100644
--- a/src/Command.php
+++ b/src/Command.php
@@ -28,6 +28,7 @@
  *     | name                       | description                                                                    |
  *     +----------------------------+--------------------------------------------------------------------------------+
  *     | autoload-options-size      | Warns when autoloaded options size exceeds threshold of 900 kb.                |
+ *     | transients-size            | Warns when autoloaded transients size exceeds threshold of 900 kb.             |
  *     | constant-savequeries-falsy | Confirms expected state of the SAVEQUERIES constant.                           |
  *     | constant-wp-debug-falsy    | Confirms expected state of the WP_DEBUG constant.                              |
  *     | core-update                | Errors when new WordPress minor release is available; warns for major release. |
@@ -325,6 +326,7 @@ function ( $check ) {
 	 *     | name                       | description                                                                    |
 	 *     +----------------------------+--------------------------------------------------------------------------------+
 	 *     | autoload-options-size      | Warns when autoloaded options size exceeds threshold of 900 kb.                |
+	 *     | transients-size            | Warns when autoloaded transients size exceeds threshold of 900 kb.             |
 	 *     | constant-savequeries-falsy | Confirms expected state of the SAVEQUERIES constant.                           |
 	 *     | constant-wp-debug-falsy    | Confirms expected state of the WP_DEBUG constant.                              |
 	 *     | core-update                | Errors when new WordPress minor release is available; warns for major release. |