diff --git a/frontend/src/components/SharedSchedule.tsx b/frontend/src/components/SharedSchedule.tsx
index 6ec468f..76c1f16 100644
--- a/frontend/src/components/SharedSchedule.tsx
+++ b/frontend/src/components/SharedSchedule.tsx
@@ -535,6 +535,7 @@ export function SharedSchedule() {
 										)
 									);
 									// Count missed doses (not taken AND not dismissed)
+									// Note: SharedSchedule doesn't have updatedAt info, so we only check dismissed status
 									const missedPastDoses = totalPastDoses.filter((id) => {
 										if (takenDoses.has(id)) return false;
 										// Check if this dose is dismissed
diff --git a/frontend/src/context/AppContext.tsx b/frontend/src/context/AppContext.tsx
index 813cf7c..4a51fc3 100644
--- a/frontend/src/context/AppContext.tsx
+++ b/frontend/src/context/AppContext.tsx
@@ -419,12 +419,35 @@ export function AppProvider({ children }: { children: React.ReactNode }) {
 		return doseDateStr <= dismissedUntilDate;
 	}, []);
 
+	// Helper to check if a dose was scheduled BEFORE the medication was last updated
+	// If so, it's from a previous schedule configuration and shouldn't count as "missed"
+	const isDoseFromPreviousSchedule = useCallback(
+		(doseId: string, medUpdatedAt: string | number | null | undefined): boolean => {
+			if (!medUpdatedAt) return false; // No updatedAt means it was never changed, all doses are valid
+
+			// Extract timestamp from dose ID (format: medId-blisterIdx-timestamp or medId-blisterIdx-timestamp-person)
+			const parts = doseId.split("-");
+			if (parts.length < 3) return false;
+			const doseTimestamp = parseInt(parts[2], 10);
+			if (Number.isNaN(doseTimestamp)) return false;
+
+			// Convert updatedAt to timestamp
+			const updatedAtTimestamp = typeof medUpdatedAt === "number" ? medUpdatedAt : new Date(medUpdatedAt).getTime();
+			if (Number.isNaN(updatedAtTimestamp)) return false;
+
+			// If the dose was scheduled before the medication was updated, it's from a previous schedule
+			return doseTimestamp < updatedAtTimestamp;
+		},
+		[]
+	);
+
 	const missedPastDoseIds = useMemo(() => {
 		const totalPastDoses = pastDays.flatMap((d) =>
 			d.meds.flatMap((m) => {
-				// Find the medication to get its dismissedUntil
+				// Find the medication to get its dismissedUntil and updatedAt
 				const med = medications.meds.find((med) => med.name === m.medName);
 				const dismissedUntilDate = med?.dismissedUntil ?? undefined;
+				const medUpdatedAt = med?.updatedAt;
 
 				return m.doses.flatMap((dose) => {
 					// Check if this dose is on or before the dismissed date for this medication
@@ -432,13 +455,19 @@ export function AppProvider({ children }: { children: React.ReactNode }) {
 						return [];
 					}
 
+					// Check if this dose is from a previous schedule configuration
+					// (scheduled before the medication was last updated)
+					if (isDoseFromPreviousSchedule(dose.id, medUpdatedAt)) {
+						return [];
+					}
+
 					return (dose.takenBy || []).length > 0 ? dose.takenBy.map((p: string) => `${dose.id}-${p}`) : [dose.id];
 				});
 			})
 		);
 		// Also filter out doses that are marked as taken or individually dismissed (legacy)
 		return totalPastDoses.filter((id) => !doses.takenDoses.has(id) && !doses.dismissedDoses.has(id));
-	}, [pastDays, medications.meds, doses.takenDoses, doses.dismissedDoses, isDoseDismissed]);
+	}, [pastDays, medications.meds, doses.takenDoses, doses.dismissedDoses, isDoseDismissed, isDoseFromPreviousSchedule]);
 
 	// Modal helpers with browser history support
 	const openMedDetail = useCallback(
diff --git a/frontend/src/pages/SchedulePage.tsx b/frontend/src/pages/SchedulePage.tsx
index 6f2012c..6b6c0bb 100644
--- a/frontend/src/pages/SchedulePage.tsx
+++ b/frontend/src/pages/SchedulePage.tsx
@@ -63,6 +63,7 @@ export function SchedulePage() {
 		manuallyExpandedDays,
 		toggleDayCollapse,
 		openUserFilter,
+		missedPastDoseIds,
 	} = useAppContext();
 
 	return (
@@ -88,17 +89,11 @@ export function SchedulePage() {
 					{/* Past days toggle */}
 					{pastDays.length > 0 &&
 						(() => {
-							const totalPastDoses = pastDays.flatMap((d) =>
-								d.meds.flatMap((m) =>
-									m.doses.flatMap((dose) =>
-										(dose.takenBy || []).length > 0 ? dose.takenBy.map((p) => `${dose.id}-${p}`) : [dose.id]
-									)
-								)
-							);
-							const missedPastDoses = totalPastDoses.filter((id) => !takenDoses.has(id)).length;
+							// Use context's missedPastDoseIds which handles dismissed doses and previous schedule detection
+							const missedCount = missedPastDoseIds.length;
 							return (
 								<div
-									className={`past-days-toggle ${showPastDays ? "expanded" : ""} ${missedPastDoses > 0 ? "has-missed" : ""}`}
+									className={`past-days-toggle ${showPastDays ? "expanded" : ""} ${missedCount > 0 ? "has-missed" : ""}`}
 									onClick={() => setShowPastDays(!showPastDays)}
 								>
 									<span className="past-days-icon">{showPastDays ? "▼" : "▶"}</span>
@@ -108,12 +103,12 @@ export function SchedulePage() {
 									<span className="past-days-count">
 										({t("dashboard.schedules.pastDaysCount", { count: pastDays.length })})
 									</span>
-									{missedPastDoses > 0 && (
+									{missedCount > 0 && (
 										<span
 											className="past-days-warning"
-											title={t("dashboard.schedules.missedDoses", { count: missedPastDoses })}
+											title={t("dashboard.schedules.missedDoses", { count: missedCount })}
 										>
-											⚠️ {missedPastDoses}
+											⚠️ {missedCount}
 										</span>
 									)}
 								</div>
diff --git a/frontend/src/test/pages/SchedulePage.test.tsx b/frontend/src/test/pages/SchedulePage.test.tsx
index eeebcd0..dcdecd5 100644
--- a/frontend/src/test/pages/SchedulePage.test.tsx
+++ b/frontend/src/test/pages/SchedulePage.test.tsx
@@ -101,6 +101,7 @@ const createMockContext = (overrides = {}) => ({
 	manuallyExpandedDays: new Set(),
 	toggleDayCollapse: vi.fn(),
 	openUserFilter: vi.fn(),
+	missedPastDoseIds: [],
 	...overrides,
 });
 
@@ -436,6 +437,7 @@ describe("SchedulePage with past days", () => {
 			futureDays: mockFutureDays,
 			coverageByMed: mockCoverageByMed,
 			showPastDays: false,
+			missedPastDoseIds: [`1-0-${Date.now() - 86400000}-John`], // One missed dose
 		});
 	});
 
@@ -467,6 +469,7 @@ describe("SchedulePage with past days", () => {
 			pastDays: mockPastDays,
 			showPastDays: false,
 			setShowPastDays,
+			missedPastDoseIds: [],
 		});
 
 		render(