diff --git a/public/app/plugins/datasource/prometheus/configuration/PromSettings.test.tsx b/public/app/plugins/datasource/prometheus/configuration/PromSettings.test.tsx
index 5953f0fc000..ae426979d3d 100644
--- a/public/app/plugins/datasource/prometheus/configuration/PromSettings.test.tsx
+++ b/public/app/plugins/datasource/prometheus/configuration/PromSettings.test.tsx
@@ -1,7 +1,9 @@
-import { getValueFromEventItem, promSettingsValidationEvents } from './PromSettings';
+import React, { SyntheticEvent } from 'react';
+import { render, screen } from '@testing-library/react';
 import { EventsWithValidation } from '@grafana/ui';
-import { SyntheticEvent } from 'react';
 import { SelectableValue } from '@grafana/data';
+import { getValueFromEventItem, promSettingsValidationEvents, PromSettings } from './PromSettings';
+import { createDefaultConfigOptions } from './mocks';
 
 describe('PromSettings', () => {
   describe('getValueFromEventItem', () => {
@@ -83,4 +85,56 @@ describe('PromSettings', () => {
       }
     );
   });
+  describe('PromSettings component', () => {
+    const defaultProps = createDefaultConfigOptions();
+
+    it('should show POST httpMethod if no httpMethod and no url', () => {
+      const options = defaultProps;
+      options.url = '';
+      options.jsonData.httpMethod = '';
+
+      render(
+        <div>
+          <PromSettings onOptionsChange={() => {}} options={options} />
+        </div>
+      );
+      expect(screen.getByText('POST')).toBeInTheDocument();
+    });
+    it('should show GET httpMethod if no httpMethod and url', () => {
+      const options = defaultProps;
+      options.url = 'test_url';
+      options.jsonData.httpMethod = '';
+
+      render(
+        <div>
+          <PromSettings onOptionsChange={() => {}} options={options} />
+        </div>
+      );
+      expect(screen.getByText('GET')).toBeInTheDocument();
+    });
+    it('should show POST httpMethod if POST httpMethod is configured', () => {
+      const options = defaultProps;
+      options.url = 'test_url';
+      options.jsonData.httpMethod = 'POST';
+
+      render(
+        <div>
+          <PromSettings onOptionsChange={() => {}} options={options} />
+        </div>
+      );
+      expect(screen.getByText('POST')).toBeInTheDocument();
+    });
+    it('should show GET httpMethod if GET httpMethod is configured', () => {
+      const options = defaultProps;
+      options.url = 'test_url';
+      options.jsonData.httpMethod = 'GET';
+
+      render(
+        <div>
+          <PromSettings onOptionsChange={() => {}} options={options} />
+        </div>
+      );
+      expect(screen.getByText('GET')).toBeInTheDocument();
+    });
+  });
 });
diff --git a/public/app/plugins/datasource/prometheus/configuration/PromSettings.tsx b/public/app/plugins/datasource/prometheus/configuration/PromSettings.tsx
index 2000232077c..6a0386d6364 100644
--- a/public/app/plugins/datasource/prometheus/configuration/PromSettings.tsx
+++ b/public/app/plugins/datasource/prometheus/configuration/PromSettings.tsx
@@ -11,8 +11,8 @@ import { ExemplarsSettings } from './ExemplarsSettings';
 const { Select, Input, FormField, Switch } = LegacyForms;
 
 const httpOptions = [
-  { value: 'GET', label: 'GET' },
   { value: 'POST', label: 'POST' },
+  { value: 'GET', label: 'GET' },
 ];
 
 type Props = Pick<DataSourcePluginOptionsEditorProps<PromOptions>, 'options' | 'onOptionsChange'>;
@@ -20,6 +20,17 @@ type Props = Pick<DataSourcePluginOptionsEditorProps<PromOptions>, 'options' | '
 export const PromSettings = (props: Props) => {
   const { options, onOptionsChange } = props;
 
+  /**
+   * We want to change the default httpMethod to 'POST' for all of the new Prometheus data sources instances (no url) added in 7.5+.
+   * We are explicitly adding httpMethod, as previously it could be undefined and defaulted to 'GET'.
+   * Undefined httpMethod is still going to be considered 'GET' for backward compatibility reasons, but if users open data
+   * source settings it is going to be set to 'GET' explicitly and it will be selected in httpMethod dropdown as 'GET'.
+   * */
+
+  if (!options.jsonData.httpMethod) {
+    options.url ? (options.jsonData.httpMethod = 'GET') : (options.jsonData.httpMethod = 'POST');
+  }
+
   return (
     <>
       <div className="gf-form-group">
@@ -64,7 +75,7 @@ export const PromSettings = (props: Props) => {
         <div className="gf-form">
           <InlineFormLabel
             width={13}
-            tooltip="Specify the HTTP Method to query Prometheus. (POST is only available in Prometheus >= v2.1.0)"
+            tooltip="You can use either POST or GET HTTP method to query your Prometheus data source. POST is the recommended method as it allows bigger queries. Change this to GET if you have a Prometheus version older than 2.1 or if POST requests are restricted in your network."
           >
             HTTP Method
           </InlineFormLabel>
diff --git a/public/app/plugins/datasource/prometheus/configuration/mocks.ts b/public/app/plugins/datasource/prometheus/configuration/mocks.ts
new file mode 100644
index 00000000000..76d9a61fa24
--- /dev/null
+++ b/public/app/plugins/datasource/prometheus/configuration/mocks.ts
@@ -0,0 +1,12 @@
+import { DataSourceSettings } from '@grafana/data';
+import { PromOptions } from '../types';
+import { createDatasourceSettings } from '../../../../features/datasources/mocks';
+
+export function createDefaultConfigOptions(): DataSourceSettings<PromOptions> {
+  return createDatasourceSettings<PromOptions>({
+    timeInterval: '1m',
+    queryTimeout: '1m',
+    httpMethod: 'GET',
+    directUrl: 'url',
+  });
+}
diff --git a/public/app/plugins/datasource/prometheus/datasource.ts b/public/app/plugins/datasource/prometheus/datasource.ts
index 3ff3d58a63f..8a7f2ebc505 100644
--- a/public/app/plugins/datasource/prometheus/datasource.ts
+++ b/public/app/plugins/datasource/prometheus/datasource.ts
@@ -83,7 +83,6 @@ export class PrometheusDatasource extends DataSourceApi<PromQuery, PromOptions>
     this.languageProvider = new PrometheusLanguageProvider(this);
     this.lookupsDisabled = instanceSettings.jsonData.disableMetricsLookup ?? false;
     this.customQueryParameters = new URLSearchParams(instanceSettings.jsonData.customQueryParameters);
-
     this.variables = new PrometheusVariableSupport(this, this.templateSrv, this.timeSrv);
   }
 
@@ -144,6 +143,7 @@ export class PrometheusDatasource extends DataSourceApi<PromQuery, PromOptions>
         data[key] = value;
       }
     }
+
     return this._request<T>(url, data, { method: 'GET', hideFromInspector: true }).toPromise(); // toPromise until we change getTagValues, getTagKeys to Observable
   }