diff --git a/apps/api/src/lib/require-user.ts b/apps/api/src/lib/require-user.ts
index 0c5dd12..3c90b90 100644
--- a/apps/api/src/lib/require-user.ts
+++ b/apps/api/src/lib/require-user.ts
@@ -4,23 +4,26 @@ import { auth } from '../auth';
 export interface SessionUser {
   id: string;
   role: string;
+  banned: boolean;
 }
 
 export async function getSessionUser(c: Context): Promise<SessionUser | null> {
   const session = await auth.api.getSession({ headers: c.req.raw.headers });
   if (!session) return null;
-  const role = (session.user as { role?: string | null }).role ?? 'worker';
-  return { id: session.user.id, role };
+  const u = session.user as { role?: string | null; banned?: boolean | null };
+  return { id: session.user.id, role: u.role ?? 'worker', banned: Boolean(u.banned) };
 }
 
 export function isAdmin(u: SessionUser | null): boolean {
   return u?.role === 'admin';
 }
 
-// Reusable gate for the whole /api/admin/* surface: 401 if unauthenticated, 403 if not an admin.
+// Reusable gate for the whole /api/admin/* surface: 401 if unauthenticated, 403 if not an
+// active admin. A banned admin is rejected even with a still-valid session (defense-in-depth
+// beyond deactivate revoking their sessions).
 export const adminGuard: MiddlewareHandler = async (c, next) => {
   const u = await getSessionUser(c);
   if (!u) return c.json({ error: 'Unauthorized' }, 401);
-  if (!isAdmin(u)) return c.json({ error: 'Forbidden' }, 403);
+  if (u.banned || !isAdmin(u)) return c.json({ error: 'Forbidden' }, 403);
   await next();
 };
diff --git a/apps/api/src/routes/admin-users.ts b/apps/api/src/routes/admin-users.ts
index e288203..928335b 100644
--- a/apps/api/src/routes/admin-users.ts
+++ b/apps/api/src/routes/admin-users.ts
@@ -57,7 +57,9 @@ adminUsersRoutes.post('/api/admin/users', async (c) => {
     return c.json({ error: 'E-mailadres bestaat al.' }, 409);
   }
 
-  const [row] = await db.select().from(user).where(eq(user.email, d.email));
+  // better-auth lowercases the email before storing, so re-select on the normalized form
+  // (zod's .email() does not lowercase) — otherwise a mixed-case email would miss and 500.
+  const [row] = await db.select().from(user).where(eq(user.email, d.email.toLowerCase()));
   return c.json(toListItem(row));
 });
 
diff --git a/apps/api/test/admin-users.test.ts b/apps/api/test/admin-users.test.ts
index 8c50f75..d43179c 100644
--- a/apps/api/test/admin-users.test.ts
+++ b/apps/api/test/admin-users.test.ts
@@ -5,6 +5,7 @@ import { authToken, bearer } from './helpers';
 import { db } from '../src/db/client';
 import { user } from '../src/db/schema';
 import { eq } from 'drizzle-orm';
+import { activeAdminsExcluding } from '../src/routes/admin-users';
 
 const PASSWORD = 'sterk-wachtwoord-123';
 
@@ -116,6 +117,23 @@ describe('POST /api/admin/users', () => {
     });
     expect(res.status).toBe(403);
   });
+
+  it('stores a mixed-case email lowercased and returns the row (no 500)', async () => {
+    const app = createApp();
+    const adminTok = await authToken(app, 'mixed-admin@example.com', 'admin');
+    const res = await app.request('/api/admin/users', {
+      method: 'POST',
+      headers: bearer(adminTok),
+      body: JSON.stringify({
+        email: 'Mixed.Case@Example.com',
+        name: 'Mixed',
+        password: PASSWORD,
+        role: 'worker',
+      }),
+    });
+    expect(res.status).toBe(200);
+    expect((await res.json()).email).toBe('mixed.case@example.com');
+  });
 });
 
 async function userIdByEmail(email: string): Promise<string> {
@@ -161,36 +179,53 @@ describe('POST /api/admin/users/:id/role', () => {
     expect((await res.json()).error).toContain('degraderen');
   });
 
-  it('refuses demoting the last active admin', async () => {
+  // Demoting *another* admin is allowed while the acting admin remains active — this is the
+  // expected 200 path. The genuine last-admin guard logic is covered as a unit test of
+  // activeAdminsExcluding below (the route branch is unreachable over HTTP because the caller
+  // is always an active admin and never the target).
+  it('allows demoting another admin while the caller stays admin', async () => {
     const app = createApp();
-    const adminTok = await authToken(app, 'role-last-admin@example.com', 'admin');
-    // Promote a worker, then that worker is the only *other* admin; demote them while the caller
-    // is also admin — but to hit the last-admin path, demote the caller's only peer after demoting caller is blocked.
-    // Simplest: single admin scenario — create a second admin, demote them (ok), then try to demote remaining peer.
+    const adminTok = await authToken(app, 'role-peer-admin@example.com', 'admin');
     await authToken(app, 'role-peer@example.com', 'admin');
     const peerId = await userIdByEmail('role-peer@example.com');
-    // Demote the peer: now caller is the only admin. Allowed (caller remains).
-    await app.request(`/api/admin/users/${peerId}/role`, {
-      method: 'POST',
-      headers: bearer(adminTok),
-      body: JSON.stringify({ role: 'worker' }),
-    });
-    // Re-promote peer, then demote caller-equivalent is blocked by self-guard; instead verify the
-    // invariant directly: ban the caller is self-blocked, so assert the helper via a constructed case.
-    // Here we assert: with only the caller as admin, demoting *any other* admin is impossible because none exist,
-    // so we validate the guard by promoting peer again and confirming a non-self demote still leaves >=1 admin (caller).
-    await app.request(`/api/admin/users/${peerId}/role`, {
-      method: 'POST',
-      headers: bearer(adminTok),
-      body: JSON.stringify({ role: 'admin' }),
-    });
     const res = await app.request(`/api/admin/users/${peerId}/role`, {
       method: 'POST',
       headers: bearer(adminTok),
       body: JSON.stringify({ role: 'worker' }),
     });
-    // caller is still admin, so demoting the peer is allowed (>=1 admin remains).
     expect(res.status).toBe(200);
+    expect((await res.json()).role).toBe('worker');
+  });
+});
+
+// Direct unit coverage of the last-admin invariant helper (the route branch that uses it is
+// unreachable over HTTP, so this is where its !banned filter + exclusion logic is actually tested).
+describe('activeAdminsExcluding', () => {
+  it('counts only active (non-banned) admins and honours the exclusion', async () => {
+    const app = createApp();
+    const before = await activeAdminsExcluding('___none___');
+
+    await authToken(app, 'aae-fresh-admin@example.com', 'admin');
+    expect(await activeAdminsExcluding('___none___')).toBe(before + 1); // a new active admin counts
+
+    const freshId = await userIdByEmail('aae-fresh-admin@example.com');
+    expect(await activeAdminsExcluding(freshId)).toBe(before); // excluding it drops the count back
+
+    await db.update(user).set({ banned: true }).where(eq(user.id, freshId));
+    expect(await activeAdminsExcluding('___none___')).toBe(before); // a banned admin is not counted
+  });
+});
+
+describe('adminGuard rejects banned admins', () => {
+  it('403s a banned admin that still holds a valid token', async () => {
+    const app = createApp();
+    const adminTok = await authToken(app, 'banned-admin@example.com', 'admin');
+    expect((await app.request('/api/admin/users', { headers: bearer(adminTok) })).status).toBe(200);
+
+    // Ban directly (not via /deactivate, which would also delete the session) so the token stays valid.
+    const id = await userIdByEmail('banned-admin@example.com');
+    await db.update(user).set({ banned: true }).where(eq(user.id, id));
+    expect((await app.request('/api/admin/users', { headers: bearer(adminTok) })).status).toBe(403);
   });
 });
 
@@ -250,10 +285,11 @@ describe('deactivate / reactivate', () => {
     expect((await res.json()).error).toContain('deactiveren');
   });
 
-  it('refuses deactivating the last active admin', async () => {
+  // Deactivating another admin is allowed (the caller remains); the caller can never deactivate
+  // themselves even as the sole remaining active admin — together these preserve the invariant.
+  it('allows deactivating another admin but always blocks self-deactivate', async () => {
     const app = createApp();
     const adminTok = await authToken(app, 'deact-last-admin@example.com', 'admin');
-    // promote a peer, deactivate caller is self-blocked; deactivate the peer is allowed (caller remains).
     await authToken(app, 'deact-peer@example.com', 'admin');
     const peerId = await userIdByEmail('deact-peer@example.com');
     const res = await app.request(`/api/admin/users/${peerId}/deactivate`, {
@@ -261,13 +297,14 @@ describe('deactivate / reactivate', () => {
       headers: bearer(adminTok),
     });
     expect(res.status).toBe(200); // caller still admin → allowed
-    // Now the peer is inactive; the caller is the only active admin. Deactivating self is blocked:
+
+    // The caller is now the only active admin; deactivating self is refused.
     const callerId = await userIdByEmail('deact-last-admin@example.com');
     const selfRes = await app.request(`/api/admin/users/${callerId}/deactivate`, {
       method: 'POST',
       headers: bearer(adminTok),
     });
-    expect(selfRes.status).toBe(400); // self-guard (which also preserves the last admin)
+    expect(selfRes.status).toBe(400);
   });
 
   it('404s on an unknown id and 403s for a worker', async () => {