diff --git a/src/datasource/components/ItemCountWarning.tsx b/src/datasource/components/ItemCountWarning.tsx
new file mode 100644
index 0000000..cf80aec
--- /dev/null
+++ b/src/datasource/components/ItemCountWarning.tsx
@@ -0,0 +1,27 @@
+import React from 'react';
+import { Alert } from '@grafana/ui';
+import { ITEM_COUNT_WARNING_THRESHOLD } from '../constants';
+
+interface ItemCountWarningProps {
+  itemCount: number;
+  threshold?: number;
+}
+
+/**
+ * A warning banner that displays when the query matches too many items.
+ * This is a non-intrusive warning that doesn't block the query flow.
+ */
+export const ItemCountWarning: React.FC<ItemCountWarningProps> = ({
+  itemCount,
+  threshold = ITEM_COUNT_WARNING_THRESHOLD,
+}) => {
+  if (itemCount < threshold) {
+    return null;
+  }
+
+  return (
+    <Alert title="Large number of items" severity="warning">
+      This query matches {itemCount} items and may return a large amount of data. Consider using more specific filters.
+    </Alert>
+  );
+};
diff --git a/src/datasource/components/QueryEditor.tsx b/src/datasource/components/QueryEditor.tsx
index 111b1ad..646ec71 100644
--- a/src/datasource/components/QueryEditor.tsx
+++ b/src/datasource/components/QueryEditor.tsx
@@ -1,4 +1,4 @@
-import React, { useEffect } from 'react';
+import React, { useEffect, useState } from 'react';
 import { QueryEditorProps } from '@grafana/data';
 import { Combobox, ComboboxOption, InlineField, Stack } from '@grafana/ui';
 import * as c from '../constants';
@@ -16,6 +16,7 @@ import { ServicesQueryEditor } from './QueryEditor/ServicesQueryEditor';
 import { TriggersQueryEditor } from './QueryEditor/TriggersQueryEditor';
 import { UserMacrosQueryEditor } from './QueryEditor/UserMacrosQueryEditor';
 import { QueryEditorRow } from './QueryEditor/QueryEditorRow';
+import { ItemCountWarning } from './ItemCountWarning';
 
 const zabbixQueryTypeOptions: Array<ComboboxOption<QueryType>> = [
   {
@@ -113,6 +114,7 @@ export interface ZabbixQueryEditorProps
   extends QueryEditorProps<ZabbixDatasource, ZabbixMetricsQuery, ZabbixDSOptions> {}
 
 export const QueryEditor = ({ query, datasource, onChange, onRunQuery }: ZabbixQueryEditorProps) => {
+  const [itemCount, setItemCount] = useState(0);
   const queryDefaults = getDefaultQuery();
   query = { ...queryDefaults, ...query };
   query.options = { ...queryDefaults.options, ...query.options };
@@ -152,7 +154,12 @@ export const QueryEditor = ({ query, datasource, onChange, onRunQuery }: ZabbixQ
   const renderMetricsEditor = () => {
     return (
       <>
-        <MetricsQueryEditor query={query} datasource={datasource} onChange={onChangeInternal} />
+        <MetricsQueryEditor
+          query={query}
+          datasource={datasource}
+          onChange={onChangeInternal}
+          onItemCountChange={setItemCount}
+        />
         <QueryFunctionsEditor query={query} onChange={onChangeInternal} />
       </>
     );
@@ -198,6 +205,7 @@ export const QueryEditor = ({ query, datasource, onChange, onRunQuery }: ZabbixQ
 
   return (
     <Stack direction="column">
+      {queryType === c.MODE_METRICS && <ItemCountWarning itemCount={itemCount} />}
       <QueryEditorRow>
         <InlineField label="Query type" labelWidth={12}>
           <Combobox<QueryType>
diff --git a/src/datasource/components/QueryEditor/MetricsQueryEditor.tsx b/src/datasource/components/QueryEditor/MetricsQueryEditor.tsx
index d416994..2907103 100644
--- a/src/datasource/components/QueryEditor/MetricsQueryEditor.tsx
+++ b/src/datasource/components/QueryEditor/MetricsQueryEditor.tsx
@@ -16,9 +16,10 @@ export interface Props {
   query: ZabbixMetricsQuery;
   datasource: ZabbixDatasource;
   onChange: (query: ZabbixMetricsQuery) => void;
+  onItemCountChange?: (count: number) => void;
 }
 
-export const MetricsQueryEditor = ({ query, datasource, onChange }: Props) => {
+export const MetricsQueryEditor = ({ query, datasource, onChange, onItemCountChange }: Props) => {
   const interpolatedQuery = useInterpolatedQuery(datasource, query);
 
   const loadGroupOptions = async () => {
@@ -94,12 +95,30 @@ export const MetricsQueryEditor = ({ query, datasource, onChange }: Props) => {
     return options;
   }, [interpolatedQuery.group.filter, interpolatedQuery.host.filter]);
 
-  const loadItemOptions = async (group: string, host: string, app: string, itemTag: string) => {
+  const loadItemOptions = async (group: string, host: string, app: string, itemTag: string, itemFilter: string) => {
     const options = {
       itemtype: 'num',
       showDisabledItems: query.options.showDisabledItems,
     };
     const items = await datasource.zabbix.getAllItems(group, host, app, itemTag, options);
+
+    // Count items that match the current item filter for the warning
+    let matchingItemCount = items?.length || 0;
+    if (itemFilter && items?.length) {
+      // If there's an item filter, count how many items match it
+      const filterRegex =
+        itemFilter.startsWith('/') && itemFilter.endsWith('/') ? new RegExp(itemFilter.slice(1, -1)) : null;
+      if (filterRegex) {
+        matchingItemCount = items.filter((item) => filterRegex.test(item.name)).length;
+      } else if (itemFilter) {
+        // Exact match or partial match
+        matchingItemCount = items.filter((item) => item.name === itemFilter || item.name.includes(itemFilter)).length;
+      }
+    }
+
+    // Report the matching item count
+    onItemCountChange?.(matchingItemCount);
+
     let itemOptions: Array<ComboboxOption<string>> = items?.map((item) => ({
       value: item.name,
       label: item.name,
@@ -114,7 +133,8 @@ export const MetricsQueryEditor = ({ query, datasource, onChange }: Props) => {
       interpolatedQuery.group.filter,
       interpolatedQuery.host.filter,
       interpolatedQuery.application.filter,
-      interpolatedQuery.itemTag.filter
+      interpolatedQuery.itemTag.filter,
+      interpolatedQuery.item.filter
     );
     return options;
   }, [
@@ -122,6 +142,7 @@ export const MetricsQueryEditor = ({ query, datasource, onChange }: Props) => {
     interpolatedQuery.host.filter,
     interpolatedQuery.application.filter,
     interpolatedQuery.itemTag.filter,
+    interpolatedQuery.item.filter,
   ]);
 
   // Update suggestions on every metric change
@@ -129,6 +150,7 @@ export const MetricsQueryEditor = ({ query, datasource, onChange }: Props) => {
   const hostFilter = interpolatedQuery.host?.filter;
   const appFilter = interpolatedQuery.application?.filter;
   const tagFilter = interpolatedQuery.itemTag?.filter;
+  const itemFilter = interpolatedQuery.item?.filter;
 
   useEffect(() => {
     fetchGroups();
@@ -148,7 +170,7 @@ export const MetricsQueryEditor = ({ query, datasource, onChange }: Props) => {
 
   useEffect(() => {
     fetchItems();
-  }, [groupFilter, hostFilter, appFilter, tagFilter]);
+  }, [groupFilter, hostFilter, appFilter, tagFilter, itemFilter]);
 
   const onFilterChange = (prop: string) => {
     return (value: string) => {
diff --git a/src/datasource/constants.ts b/src/datasource/constants.ts
index a087a2c..29d4e98 100644
--- a/src/datasource/constants.ts
+++ b/src/datasource/constants.ts
@@ -49,3 +49,5 @@ export const MIN_SLA_INTERVAL = 3600;
 export const RANGE_VARIABLE_VALUE = 'range_series';
 
 export const DEFAULT_ZABBIX_PROBLEMS_LIMIT = 1001;
+
+export const ITEM_COUNT_WARNING_THRESHOLD = 500;