diff --git a/frontend/src/App.tsx b/frontend/src/App.tsx
index cd84e1d..753d53a 100644
--- a/frontend/src/App.tsx
+++ b/frontend/src/App.tsx
@@ -1,19 +1,29 @@
 import { BrowserRouter, Routes, Route, Navigate } from 'react-router-dom'
 import { LoginPage } from './pages/Login'
 import { SignupPage } from './pages/Signup'
-import { Dashboard } from './pages/Dashboard'
+import { DashboardPage } from './pages/Dashboard'
 import { ProfilePage } from './pages/Profile'
+import { InsightsPage } from './pages/Insights'
+import { SourcesPage } from './pages/Sources'
 import { AdminPage } from './pages/Admin'
+import { Layout } from './components/Layout'
 
 function App() {
   return (
     <BrowserRouter>
       <Routes>
+        {/* Public routes */}
         <Route path="/login" element={<LoginPage />} />
         <Route path="/signup" element={<SignupPage />} />
-        <Route path="/profile" element={<ProfilePage />} />
-        <Route path="/admin" element={<AdminPage />} />
-        <Route path="/" element={<Dashboard />} />
+
+        {/* Protected routes with Layout */}
+        <Route path="/" element={<Layout><DashboardPage /></Layout>} />
+        <Route path="/profile" element={<Layout><ProfilePage /></Layout>} />
+        <Route path="/insights" element={<Layout><InsightsPage /></Layout>} />
+        <Route path="/sources" element={<Layout><SourcesPage /></Layout>} />
+        <Route path="/admin" element={<Layout><AdminPage /></Layout>} />
+
+        {/* Fallback */}
         <Route path="*" element={<Navigate to="/" replace />} />
       </Routes>
     </BrowserRouter>
diff --git a/frontend/src/components/Layout.tsx b/frontend/src/components/Layout.tsx
new file mode 100644
index 0000000..2eaafb7
--- /dev/null
+++ b/frontend/src/components/Layout.tsx
@@ -0,0 +1,148 @@
+import { useEffect, useState, type ReactNode } from 'react'
+import { useNavigate, useLocation, Link } from 'react-router-dom'
+
+interface User {
+    id: number
+    username: string
+    name: string | null
+    role: string
+}
+
+interface LayoutProps {
+    children: ReactNode
+}
+
+export function Layout({ children }: LayoutProps) {
+    const navigate = useNavigate()
+    const location = useLocation()
+    const [user, setUser] = useState<User | null>(null)
+    const [loading, setLoading] = useState(true)
+    const [theme, setTheme] = useState(() =>
+        document.documentElement.getAttribute('data-theme') || 'light'
+    )
+
+    useEffect(() => {
+        fetch('/api/auth/me', { credentials: 'include' })
+            .then(res => res.json())
+            .then(data => {
+                if (!data.user) {
+                    navigate('/login')
+                    return null
+                }
+                return fetch(`/api/users/${data.user.id}`, { credentials: 'include' })
+                    .then(res => res.json())
+            })
+            .then((profile) => {
+                if (profile) {
+                    setUser(profile)
+                }
+            })
+            .catch(() => navigate('/login'))
+            .finally(() => setLoading(false))
+    }, [navigate])
+
+    const handleLogout = async () => {
+        await fetch('/api/auth/logout', {
+            method: 'POST',
+            credentials: 'include',
+        })
+        navigate('/login')
+    }
+
+    const toggleTheme = () => {
+        const newTheme = theme === 'dark' ? 'light' : 'dark'
+        document.documentElement.setAttribute('data-theme', newTheme)
+        localStorage.setItem('theme', newTheme)
+        setTheme(newTheme)
+    }
+
+    if (loading) {
+        return <div className="layout-loading">Loading...</div>
+    }
+
+    if (!user) {
+        return null
+    }
+
+    const displayName = user.name || user.username
+
+    const navItems = [
+        { path: '/', label: 'Dashboard', icon: '📊' },
+        { path: '/profile', label: 'Profile', icon: '👤' },
+        { path: '/insights', label: 'Insights', icon: '💡', disabled: true },
+        { path: '/sources', label: 'Sources', icon: '📄' },
+    ]
+
+    return (
+        <div className="app-layout">
+            {/* Sidebar */}
+            <aside className="sidebar">
+                <div className="sidebar-header">
+                    <img src="/logo.svg" alt="zhealth" className="sidebar-logo" />
+                    <span className="sidebar-title">zhealth</span>
+                </div>
+
+                <nav className="sidebar-nav">
+                    {navItems.map(item => (
+                        <Link
+                            key={item.path}
+                            to={item.disabled ? '#' : item.path}
+                            className={`sidebar-link ${location.pathname === item.path ? 'active' : ''} ${item.disabled ? 'disabled' : ''}`}
+                            onClick={e => item.disabled && e.preventDefault()}
+                        >
+                            <span className="sidebar-icon">{item.icon}</span>
+                            <span className="sidebar-label">{item.label}</span>
+                            {item.disabled && <span className="sidebar-badge">Soon</span>}
+                        </Link>
+                    ))}
+                </nav>
+
+                {/* Admin link for admins */}
+                {user.role === 'admin' && (
+                    <div className="sidebar-section">
+                        <div className="sidebar-section-title">Admin</div>
+                        <Link
+                            to="/admin"
+                            className={`sidebar-link ${location.pathname === '/admin' ? 'active' : ''}`}
+                        >
+                            <span className="sidebar-icon">⚙️</span>
+                            <span className="sidebar-label">Manage Users</span>
+                        </Link>
+                    </div>
+                )}
+
+                <div className="sidebar-footer">
+                    <div className="sidebar-user">
+                        <div className="sidebar-user-name">{displayName}</div>
+                        <div className="sidebar-user-role">
+                            <span className={`indicator indicator-${user.role === 'admin' ? 'warning' : 'info'}`}>
+                                {user.role}
+                            </span>
+                        </div>
+                    </div>
+                    <div className="sidebar-actions">
+                        <button
+                            className="sidebar-btn"
+                            onClick={toggleTheme}
+                            title={theme === 'dark' ? 'Light mode' : 'Dark mode'}
+                        >
+                            {theme === 'dark' ? '☀️' : '🌙'}
+                        </button>
+                        <button
+                            className="sidebar-btn"
+                            onClick={handleLogout}
+                            title="Logout"
+                        >
+                            🚪
+                        </button>
+                    </div>
+                </div>
+            </aside>
+
+            {/* Main Content */}
+            <main className="main-content">
+                {children}
+            </main>
+        </div>
+    )
+}
diff --git a/frontend/src/index.css b/frontend/src/index.css
index 3341371..d62e6d6 100644
--- a/frontend/src/index.css
+++ b/frontend/src/index.css
@@ -420,4 +420,186 @@ select.input {
 .biomarker-unit {
   color: var(--text-secondary);
   font-size: 11px;
+}
+
+/* App Layout with Sidebar */
+.app-layout {
+  display: flex;
+  min-height: 100vh;
+}
+
+.layout-loading {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  min-height: 100vh;
+  color: var(--text-secondary);
+}
+
+/* Sidebar */
+.sidebar {
+  width: 240px;
+  background: var(--bg-secondary);
+  border-right: 1px solid var(--border);
+  display: flex;
+  flex-direction: column;
+  position: fixed;
+  height: 100vh;
+  left: 0;
+  top: 0;
+}
+
+.sidebar-header {
+  padding: var(--space-md);
+  display: flex;
+  align-items: center;
+  gap: var(--space-sm);
+  border-bottom: 1px solid var(--border);
+}
+
+.sidebar-logo {
+  width: 28px;
+  height: 28px;
+}
+
+.sidebar-title {
+  font-size: 18px;
+  font-weight: 600;
+}
+
+.sidebar-nav {
+  flex: 1;
+  padding: var(--space-sm);
+  overflow-y: auto;
+}
+
+.sidebar-link {
+  display: flex;
+  align-items: center;
+  gap: var(--space-sm);
+  padding: var(--space-sm) var(--space-md);
+  border-radius: var(--radius-md);
+  color: var(--text-secondary);
+  text-decoration: none;
+  font-size: 14px;
+  margin-bottom: 2px;
+  transition: background-color 0.15s, color 0.15s;
+}
+
+.sidebar-link:hover {
+  background-color: var(--bg-primary);
+  color: var(--text-primary);
+  text-decoration: none;
+}
+
+.sidebar-link.active {
+  background-color: var(--accent);
+  color: white;
+}
+
+.sidebar-link.disabled {
+  opacity: 0.5;
+  cursor: not-allowed;
+}
+
+.sidebar-link.disabled:hover {
+  background-color: transparent;
+  color: var(--text-secondary);
+}
+
+.sidebar-icon {
+  font-size: 16px;
+}
+
+.sidebar-label {
+  flex: 1;
+}
+
+.sidebar-badge {
+  font-size: 10px;
+  padding: 2px 6px;
+  background: var(--border);
+  color: var(--text-secondary);
+  border-radius: 9999px;
+}
+
+.sidebar-section {
+  padding: var(--space-sm);
+  border-top: 1px solid var(--border);
+}
+
+.sidebar-section-title {
+  font-size: 11px;
+  text-transform: uppercase;
+  color: var(--text-secondary);
+  padding: var(--space-xs) var(--space-md);
+  margin-bottom: var(--space-xs);
+}
+
+.sidebar-footer {
+  padding: var(--space-md);
+  border-top: 1px solid var(--border);
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+}
+
+.sidebar-user {
+  min-width: 0;
+  display: flex;
+  align-items: center;
+  gap: var(--space-sm);
+}
+
+.sidebar-user-name {
+  font-size: 14px;
+  font-weight: 500;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.sidebar-actions {
+  display: flex;
+  gap: var(--space-xs);
+}
+
+.sidebar-btn {
+  background: none;
+  border: 1px solid var(--border);
+  padding: var(--space-xs);
+  border-radius: var(--radius-md);
+  cursor: pointer;
+  font-size: 14px;
+  transition: background 0.15s;
+}
+
+.sidebar-btn:hover {
+  background: var(--bg-primary);
+}
+
+/* Main Content */
+.main-content {
+  flex: 1;
+  margin-left: 240px;
+  min-height: 100vh;
+  background: var(--bg-primary);
+}
+
+/* Page wrapper */
+.page {
+  padding: var(--space-lg);
+}
+
+.page-header {
+  margin-bottom: var(--space-xl);
+}
+
+.page-header h1 {
+  margin-bottom: var(--space-xs);
+}
+
+.page-loading {
+  padding: var(--space-lg);
+  color: var(--text-secondary);
 }
\ No newline at end of file
diff --git a/frontend/src/pages/Dashboard.tsx b/frontend/src/pages/Dashboard.tsx
index 4569e52..005acfe 100644
--- a/frontend/src/pages/Dashboard.tsx
+++ b/frontend/src/pages/Dashboard.tsx
@@ -1,12 +1,4 @@
 import { useEffect, useState } from 'react'
-import { useNavigate, Link } from 'react-router-dom'
-
-interface User {
-    id: number
-    username: string
-    name: string | null
-    role: string
-}
 
 interface Category {
     id: number
@@ -23,62 +15,22 @@ interface Biomarker {
     methodology: string | null
 }
 
-export function Dashboard() {
-    const navigate = useNavigate()
-    const [user, setUser] = useState<User | null>(null)
-    const [loading, setLoading] = useState(true)
-    const [theme, setTheme] = useState(() =>
-        document.documentElement.getAttribute('data-theme') || 'light'
-    )
+export function DashboardPage() {
     const [categories, setCategories] = useState<Category[]>([])
     const [biomarkers, setBiomarkers] = useState<Biomarker[]>([])
     const [expandedCategories, setExpandedCategories] = useState<Set<number>>(new Set())
+    const [loading, setLoading] = useState(true)
 
     useEffect(() => {
-        // First get auth info, then fetch full user profile for name
-        fetch('/api/auth/me', { credentials: 'include' })
-            .then(res => res.json())
-            .then(data => {
-                if (!data.user) {
-                    navigate('/login')
-                    return null
-                }
-                // Fetch full user profile to get name
-                return fetch(`/api/users/${data.user.id}`, { credentials: 'include' })
-                    .then(res => res.json())
-            })
-            .then((profile) => {
-                if (profile) {
-                    setUser(profile)
-                }
-            })
-            .catch(() => navigate('/login'))
-            .finally(() => setLoading(false))
-
-        // Fetch categories and biomarkers
         Promise.all([
             fetch('/api/categories', { credentials: 'include' }).then(r => r.json()),
             fetch('/api/biomarkers', { credentials: 'include' }).then(r => r.json()),
         ]).then(([cats, bms]) => {
             setCategories(cats)
             setBiomarkers(bms)
+            setLoading(false)
         })
-    }, [navigate])
-
-    const handleLogout = async () => {
-        await fetch('/api/auth/logout', {
-            method: 'POST',
-            credentials: 'include',
-        })
-        navigate('/login')
-    }
-
-    const toggleTheme = () => {
-        const newTheme = theme === 'dark' ? 'light' : 'dark'
-        document.documentElement.setAttribute('data-theme', newTheme)
-        localStorage.setItem('theme', newTheme)
-        setTheme(newTheme)
-    }
+    }, [])
 
     const toggleCategory = (categoryId: number) => {
         setExpandedCategories(prev => {
@@ -97,69 +49,18 @@ export function Dashboard() {
     }
 
     if (loading) {
-        return <div style={{ padding: 'var(--space-lg)' }}>Loading...</div>
+        return <div className="page-loading">Loading biomarkers...</div>
     }
 
-    if (!user) {
-        return null
-    }
-
-    // Display name or username fallback
-    const displayName = user.name || user.username
-
     return (
-        <div style={{ padding: 'var(--space-lg)' }}>
-            <header style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'center', marginBottom: 'var(--space-xl)' }}>
-                <div style={{ display: 'flex', alignItems: 'center', gap: 'var(--space-sm)' }}>
-                    <img src="/logo.svg" alt="zhealth" style={{ width: '32px', height: '32px' }} />
-                    <h1>zhealth</h1>
-                </div>
-                <div style={{ display: 'flex', gap: 'var(--space-sm)' }}>
-                    <button
-                        className="btn btn-secondary"
-                        onClick={toggleTheme}
-                        title={theme === 'dark' ? 'Switch to light mode' : 'Switch to dark mode'}
-                        style={{ fontSize: '18px', padding: 'var(--space-sm)' }}
-                    >
-                        {theme === 'dark' ? '☀️' : '🌙'}
-                    </button>
-                    <button className="btn btn-secondary" onClick={handleLogout}>
-                        Logout
-                    </button>
-                </div>
+        <div className="page">
+            <header className="page-header">
+                <h1>Dashboard</h1>
+                <p className="text-secondary">View all biomarker categories and their reference markers</p>
             </header>
 
-            <main>
-                {/* User Welcome Card */}
-                <div className="card" style={{ marginBottom: 'var(--space-lg)' }}>
-                    <div style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'flex-start' }}>
-                        <div>
-                            <h3 style={{ marginBottom: 'var(--space-sm)' }}>Welcome, {displayName}</h3>
-                            <p className="text-secondary text-sm">
-                                Role: <span className="indicator indicator-info">{user.role}</span>
-                            </p>
-                        </div>
-                        <Link to="/profile" className="btn btn-secondary">
-                            Edit Profile
-                        </Link>
-                    </div>
-                </div>
-
-                {/* Admin Section */}
-                {user.role === 'admin' && (
-                    <div className="card" style={{ marginBottom: 'var(--space-lg)' }}>
-                        <h3 style={{ marginBottom: 'var(--space-sm)' }}>Admin</h3>
-                        <p className="text-secondary text-sm" style={{ marginBottom: 'var(--space-md)' }}>
-                            Manage users and system settings
-                        </p>
-                        <Link to="/admin" className="btn btn-secondary">
-                            Manage Users
-                        </Link>
-                    </div>
-                )}
-
-                {/* Biomarker Categories */}
-                <h2 style={{ marginBottom: 'var(--space-md)' }}>Biomarkers</h2>
+            <section>
+                <h2 style={{ marginBottom: 'var(--space-md)' }}>Biomarker Categories</h2>
                 <div style={{ display: 'flex', flexDirection: 'column', gap: 'var(--space-sm)' }}>
                     {categories.map(category => {
                         const categoryBiomarkers = getBiomarkersForCategory(category.id)
@@ -167,7 +68,6 @@ export function Dashboard() {
 
                         return (
                             <div key={category.id} className="card" style={{ padding: 0 }}>
-                                {/* Category Header - Clickable */}
                                 <button
                                     className="collapsible-header"
                                     onClick={() => toggleCategory(category.id)}
@@ -195,7 +95,6 @@ export function Dashboard() {
                                     </span>
                                 </button>
 
-                                {/* Biomarkers List - Collapsible */}
                                 {isExpanded && (
                                     <div style={{ borderTop: '1px solid var(--border)', padding: 'var(--space-sm)' }}>
                                         {categoryBiomarkers.length === 0 ? (
@@ -222,7 +121,7 @@ export function Dashboard() {
                         )
                     })}
                 </div>
-            </main>
+            </section>
         </div>
     )
 }
diff --git a/frontend/src/pages/Insights.tsx b/frontend/src/pages/Insights.tsx
new file mode 100644
index 0000000..c187bce
--- /dev/null
+++ b/frontend/src/pages/Insights.tsx
@@ -0,0 +1,18 @@
+export function InsightsPage() {
+    return (
+        <div className="page">
+            <header className="page-header">
+                <h1>Insights</h1>
+                <p className="text-secondary">AI-powered analysis of your health data</p>
+            </header>
+
+            <div className="card" style={{ textAlign: 'center', padding: 'var(--space-xl)' }}>
+                <div style={{ fontSize: '48px', marginBottom: 'var(--space-md)' }}>🚀</div>
+                <h3>Coming Soon</h3>
+                <p className="text-secondary">
+                    AI-generated health insights and recommendations based on your biomarker data.
+                </p>
+            </div>
+        </div>
+    )
+}
diff --git a/frontend/src/pages/Profile.tsx b/frontend/src/pages/Profile.tsx
index a2916b7..4c70117 100644
--- a/frontend/src/pages/Profile.tsx
+++ b/frontend/src/pages/Profile.tsx
@@ -1,5 +1,4 @@
 import { useEffect, useState } from 'react'
-import { useNavigate, Link } from 'react-router-dom'
 
 interface Diet {
     id: number
@@ -21,7 +20,6 @@ interface UserProfile {
 }
 
 export function ProfilePage() {
-    const navigate = useNavigate()
     const [loading, setLoading] = useState(true)
     const [saving, setSaving] = useState(false)
     const [message, setMessage] = useState<{ type: 'success' | 'error'; text: string } | null>(null)
@@ -39,19 +37,16 @@ export function ProfilePage() {
     const [dietId, setDietId] = useState<number | null>(null)
 
     useEffect(() => {
-        // Fetch current user and diets
+        // Fetch current user and diets (Layout already ensures auth)
         Promise.all([
             fetch('/api/auth/me', { credentials: 'include' }).then(r => r.json()),
             fetch('/api/diets', { credentials: 'include' }).then(r => r.json()),
         ])
             .then(([authData, dietsData]) => {
-                if (!authData.user) {
-                    navigate('/login')
-                    return
-                }
+                if (!authData.user) return
                 setDiets(dietsData)
 
-                // Now fetch full user profile
+                // Fetch full user profile
                 return fetch(`/api/users/${authData.user.id}`, { credentials: 'include' })
                     .then(r => r.json())
                     .then((profile: UserProfile) => {
@@ -68,9 +63,8 @@ export function ProfilePage() {
                         setDietId(diet?.id || null)
                     })
             })
-            .catch(() => navigate('/login'))
             .finally(() => setLoading(false))
-    }, [navigate])
+    }, [])
 
     const handleSubmit = async (e: React.FormEvent) => {
         e.preventDefault()
@@ -108,14 +102,14 @@ export function ProfilePage() {
     }
 
     if (loading) {
-        return <div style={{ padding: 'var(--space-lg)' }}>Loading...</div>
+        return <div className="page-loading">Loading...</div>
     }
 
     return (
-        <div style={{ padding: 'var(--space-lg)', maxWidth: '600px', margin: '0 auto' }}>
-            <header style={{ marginBottom: 'var(--space-xl)' }}>
-                <Link to="/" className="text-secondary text-sm">← Back to Dashboard</Link>
-                <h1 style={{ marginTop: 'var(--space-sm)' }}>Profile</h1>
+        <div className="page" style={{ maxWidth: '600px' }}>
+            <header className="page-header">
+                <h1>Profile</h1>
+                <p className="text-secondary">Manage your account and health information</p>
             </header>
 
             <form onSubmit={handleSubmit}>
diff --git a/frontend/src/pages/Sources.tsx b/frontend/src/pages/Sources.tsx
new file mode 100644
index 0000000..edcacc0
--- /dev/null
+++ b/frontend/src/pages/Sources.tsx
@@ -0,0 +1,41 @@
+export function SourcesPage() {
+    return (
+        <div className="page">
+            <header className="page-header">
+                <h1>Sources</h1>
+                <p className="text-secondary">Upload and manage your health data sources</p>
+            </header>
+
+            <div className="card">
+                <h3 style={{ marginBottom: 'var(--space-md)' }}>Upload Data</h3>
+                <p className="text-secondary text-sm" style={{ marginBottom: 'var(--space-lg)' }}>
+                    Upload lab reports in PDF, CSV, or Excel format to import your biomarker data.
+                </p>
+
+                <div
+                    className="upload-zone"
+                    style={{
+                        border: '2px dashed var(--border)',
+                        borderRadius: 'var(--radius-md)',
+                        padding: 'var(--space-xl)',
+                        textAlign: 'center',
+                        cursor: 'pointer',
+                    }}
+                >
+                    <div style={{ fontSize: '36px', marginBottom: 'var(--space-sm)' }}>📤</div>
+                    <p className="text-secondary">
+                        Drag & drop files here, or click to browse
+                    </p>
+                    <p className="text-secondary text-xs" style={{ marginTop: 'var(--space-sm)' }}>
+                        Supported: PDF, CSV, XLSX
+                    </p>
+                </div>
+            </div>
+
+            <div className="card" style={{ marginTop: 'var(--space-lg)' }}>
+                <h3 style={{ marginBottom: 'var(--space-md)' }}>Recent Uploads</h3>
+                <p className="text-secondary text-sm">No files uploaded yet.</p>
+            </div>
+        </div>
+    )
+}