diff --git a/src/screens/AddItemScreen.tsx b/src/screens/AddItemScreen.tsx
index eaaf84f..fb3fe4d 100644
--- a/src/screens/AddItemScreen.tsx
+++ b/src/screens/AddItemScreen.tsx
@@ -8,16 +8,17 @@ import {
   InputAdornment,
 } from '@mui/material';
 import SearchIcon from '@mui/icons-material/Search';
-import { useMemo, useState } from 'react';
+import { useEffect, useMemo, useState } from 'react';
 import { useNavigate, useParams } from 'react-router-dom';
 import { v4 as uuidv4 } from 'uuid';
 import { NumericStepper } from '../components/NumericStepper';
-import { useProducts } from '../hooks/dataHooks';
+import { usePickItems, useProducts } from '../hooks/dataHooks';
 import { useDatabase } from '../context/DBProvider';
 
 export const AddItemScreen = () => {
   const { id } = useParams();
   const db = useDatabase();
+  const items = usePickItems(id);
   const products = useProducts();
   const [productId, setProductId] = useState('');
   const [query, setQuery] = useState('');
@@ -25,16 +26,33 @@ export const AddItemScreen = () => {
   const [bulk, setBulk] = useState(0);
   const navigate = useNavigate();
 
-  const filteredProducts = useMemo(
-    () =>
-      products.filter((product) =>
-        `${product.name} ${product.category}`.toLowerCase().includes(query.toLowerCase()),
-      ),
-    [products, query],
+  const existingProductIds = useMemo(
+    () => new Set(items.map((item) => item.product_id)),
+    [items],
   );
 
+  const availableProducts = useMemo(
+    () => products.filter((product) => !existingProductIds.has(product.id)),
+    [existingProductIds, products],
+  );
+
+  const filteredProducts = useMemo(
+    () =>
+      availableProducts.filter((product) =>
+        `${product.name} ${product.category}`.toLowerCase().includes(query.toLowerCase()),
+      ),
+    [availableProducts, query],
+  );
+
+  useEffect(() => {
+    if (!productId) return;
+    if (!filteredProducts.some((product) => product.id === productId)) {
+      setProductId('');
+    }
+  }, [filteredProducts, productId]);
+
   const addItem = async () => {
-    if (!id || !productId) return;
+    if (!id || !productId || existingProductIds.has(productId)) return;
     await db.pickItems.add({
       id: uuidv4(),
       pick_list_id: id,
diff --git a/src/screens/ManageAreasScreen.test.tsx b/src/screens/ManageAreasScreen.test.tsx
new file mode 100644
index 0000000..d9689d1
--- /dev/null
+++ b/src/screens/ManageAreasScreen.test.tsx
@@ -0,0 +1,51 @@
+import { MemoryRouter } from 'react-router-dom';
+import { render, screen } from '@testing-library/react';
+import userEvent from '@testing-library/user-event';
+import { describe, expect, it, vi } from 'vitest';
+import { ManageAreasScreen } from './ManageAreasScreen';
+
+const areasMock = [{ id: 'area-1', name: 'Front Counter', created_at: 0, updated_at: 0 }];
+
+vi.mock('../hooks/dataHooks', () => ({
+  useAreas: () => areasMock,
+}));
+
+const areaDeleteMock = vi.fn();
+const pickListCountMock = vi.fn();
+
+vi.mock('../context/DBProvider', () => ({
+  useDatabase: () => ({
+    areas: {
+      add: vi.fn(),
+      update: vi.fn(),
+      delete: areaDeleteMock,
+    },
+    pickLists: {
+      where: () => ({
+        equals: () => ({
+          count: pickListCountMock,
+        }),
+      }),
+    },
+  }),
+}));
+
+describe('ManageAreasScreen deletion safeguards', () => {
+  it('prevents deleting an area that is used by pick lists', async () => {
+    pickListCountMock.mockResolvedValueOnce(1);
+
+    const user = userEvent.setup();
+    render(
+      <MemoryRouter>
+        <ManageAreasScreen />
+      </MemoryRouter>,
+    );
+
+    await user.click(screen.getByRole('button', { name: /delete front counter/i }));
+
+    expect(areaDeleteMock).not.toHaveBeenCalled();
+    expect(
+      await screen.findByText(/cannot delete this area while 1 pick list\(s\) use it/i),
+    ).toBeVisible();
+  });
+});
diff --git a/src/screens/ManageAreasScreen.tsx b/src/screens/ManageAreasScreen.tsx
index 61cd5db..d84e4d8 100644
--- a/src/screens/ManageAreasScreen.tsx
+++ b/src/screens/ManageAreasScreen.tsx
@@ -1,4 +1,6 @@
 import {
+  Alert,
+  AlertColor,
   Button,
   Container,
   IconButton,
@@ -24,6 +26,7 @@ export const ManageAreasScreen = () => {
   const [name, setName] = useState('');
   const [editingAreaId, setEditingAreaId] = useState<string | null>(null);
   const [editName, setEditName] = useState('');
+  const [feedback, setFeedback] = useState<{ text: string; severity: AlertColor } | null>(null);
 
   const addArea = async () => {
     if (!name) return;
@@ -34,6 +37,7 @@ export const ManageAreasScreen = () => {
   const startEditing = (areaId: string, currentName: string) => {
     setEditingAreaId(areaId);
     setEditName(currentName);
+    setFeedback(null);
   };
 
   const saveArea = async () => {
@@ -41,6 +45,7 @@ export const ManageAreasScreen = () => {
     await db.areas.update(editingAreaId, { name: editName, updated_at: Date.now() });
     setEditingAreaId(null);
     setEditName('');
+    setFeedback({ text: 'Area updated.', severity: 'success' });
   };
 
   const cancelEditing = () => {
@@ -49,10 +54,19 @@ export const ManageAreasScreen = () => {
   };
 
   const deleteArea = async (areaId: string) => {
+    const usageCount = await db.pickLists.where('area_id').equals(areaId).count();
+    if (usageCount > 0) {
+      setFeedback({
+        text: `Cannot delete this area while ${usageCount} pick list(s) use it. Remove those lists first.`,
+        severity: 'error',
+      });
+      return;
+    }
     await db.areas.delete(areaId);
     if (editingAreaId === areaId) {
       cancelEditing();
     }
+    setFeedback({ text: 'Area deleted.', severity: 'success' });
   };
 
   return (
@@ -61,6 +75,7 @@ export const ManageAreasScreen = () => {
         Manage Areas
       </Typography>
       <Stack spacing={2}>
+        {feedback ? <Alert severity={feedback.severity}>{feedback.text}</Alert> : null}
         <Stack direction="row" spacing={1}>
           <TextField fullWidth label="Area name" value={name} onChange={(event) => setName(event.target.value)} />
           <Button variant="contained" onClick={addArea} disabled={!name}>
diff --git a/src/screens/ManageCategoriesScreen.test.tsx b/src/screens/ManageCategoriesScreen.test.tsx
new file mode 100644
index 0000000..ce7193f
--- /dev/null
+++ b/src/screens/ManageCategoriesScreen.test.tsx
@@ -0,0 +1,59 @@
+import { MemoryRouter } from 'react-router-dom';
+import { render, screen } from '@testing-library/react';
+import userEvent from '@testing-library/user-event';
+import { describe, expect, it, vi } from 'vitest';
+import { ManageCategoriesScreen } from './ManageCategoriesScreen';
+
+const categoriesMock = [{ id: 'cat-1', name: 'Snacks', created_at: 0, updated_at: 0 }];
+const productsMock = [
+  {
+    id: 'prod-1',
+    name: 'Chips',
+    category: 'Snacks',
+    archived: false,
+    created_at: 0,
+    updated_at: 0,
+  },
+];
+
+vi.mock('../hooks/dataHooks', () => ({
+  useCategories: () => categoriesMock,
+  useProducts: () => productsMock,
+}));
+
+const categoryDeleteMock = vi.fn();
+
+vi.mock('../context/DBProvider', () => ({
+  useDatabase: () => ({
+    categories: {
+      add: vi.fn(),
+      update: vi.fn(),
+      delete: categoryDeleteMock,
+    },
+    products: {
+      where: () => ({
+        equals: () => ({
+          modify: vi.fn(),
+        }),
+      }),
+    },
+  }),
+}));
+
+describe('ManageCategoriesScreen deletion safeguards', () => {
+  it('shows an error when trying to delete an in-use category', async () => {
+    const user = userEvent.setup();
+    render(
+      <MemoryRouter>
+        <ManageCategoriesScreen />
+      </MemoryRouter>,
+    );
+
+    await user.click(screen.getByRole('button', { name: /delete snacks/i }));
+
+    expect(categoryDeleteMock).not.toHaveBeenCalled();
+    expect(
+      await screen.findByText(/cannot delete 'snacks' while 1 product\(s\) use it/i),
+    ).toBeVisible();
+  });
+});
diff --git a/src/screens/ManageProductsScreen.test.tsx b/src/screens/ManageProductsScreen.test.tsx
index ce55e41..8d39606 100644
--- a/src/screens/ManageProductsScreen.test.tsx
+++ b/src/screens/ManageProductsScreen.test.tsx
@@ -24,6 +24,9 @@ vi.mock('../hooks/dataHooks', () => ({
   useCategories: () => mockUseCategories(),
 }));
 
+const productDeleteMock = vi.fn();
+const pickItemCountMock = vi.fn();
+
 vi.mock('../context/DBProvider', () => ({
   useDatabase: () => mockDb,
 }));
@@ -161,3 +164,21 @@ describe('ManageProductsScreen barcode lookup', () => {
   });
 });
 
+describe('ManageProductsScreen deletion safeguards', () => {
+  it('blocks deletion when pick items reference the product', async () => {
+    pickItemCountMock.mockResolvedValueOnce(2);
+
+    const user = userEvent.setup();
+    render(
+      <MemoryRouter>
+        <ManageProductsScreen />
+      </MemoryRouter>,
+    );
+
+    await user.click(screen.getByRole('button', { name: /delete chips/i }));
+
+    expect(productDeleteMock).not.toHaveBeenCalled();
+    expect(await screen.findByText(/cannot delete this product while 2 pick item\(s\) reference it/i)).toBeVisible();
+  });
+});
+
diff --git a/src/screens/ManageProductsScreen.tsx b/src/screens/ManageProductsScreen.tsx
index e1d6b22..6d6dd02 100644
--- a/src/screens/ManageProductsScreen.tsx
+++ b/src/screens/ManageProductsScreen.tsx
@@ -1,14 +1,16 @@
 import {
+  Alert,
+  AlertColor,
   Button,
   Container,
+  Dialog,
+  DialogContent,
+  DialogTitle,
+  InputAdornment,
   MenuItem,
   Stack,
   TextField,
   Typography,
-  InputAdornment,
-  Dialog,
-  DialogTitle,
-  DialogContent,
 } from '@mui/material';
 import SearchIcon from '@mui/icons-material/Search';
 import { Link as RouterLink, useLocation } from 'react-router-dom';
@@ -36,6 +38,7 @@ export const ManageProductsScreen = () => {
     'idle',
   );
   const [externalProduct, setExternalProduct] = useState<ExternalProductInfo | null>(null);
+  const [feedback, setFeedback] = useState<{ text: string; severity: AlertColor } | null>(null);
 
   const lookupBarcode = useCallback(async (code: string) => {
     if (!code) return;
@@ -148,6 +151,7 @@ export const ManageProductsScreen = () => {
     });
     setName('');
     setBarcode('');
+    setFeedback({ text: 'Product added.', severity: 'success' });
   };
 
   const updateProduct = async (
@@ -166,10 +170,20 @@ export const ManageProductsScreen = () => {
       bulk_name: DEFAULT_BULK_NAME,
       updated_at: Date.now(),
     });
+    setFeedback({ text: 'Product updated.', severity: 'success' });
   };
 
   const deleteProduct = async (productId: string) => {
+    const usageCount = await db.pickItems.where('product_id').equals(productId).count();
+    if (usageCount > 0) {
+      setFeedback({
+        text: `Cannot delete this product while ${usageCount} pick item(s) reference it. Remove those items first.`,
+        severity: 'error',
+      });
+      return;
+    }
     await db.products.delete(productId);
+    setFeedback({ text: 'Product deleted.', severity: 'success' });
   };
 
   return (
@@ -178,6 +192,7 @@ export const ManageProductsScreen = () => {
         Manage Products
       </Typography>
       <Stack spacing={2}>
+        {feedback ? <Alert severity={feedback.severity}>{feedback.text}</Alert> : null}
         <Button component={RouterLink} to="/categories" variant="outlined" sx={{ alignSelf: 'flex-start' }}>
           Edit Categories
         </Button>