diff --git a/scripts/seed-demo.ts b/scripts/seed-demo.ts
index 44d4db708..7bc70996b 100644
--- a/scripts/seed-demo.ts
+++ b/scripts/seed-demo.ts
@@ -13,6 +13,7 @@
  */
 
 import pg from "pg";
+import { VALUE_RANGES } from "../src/lib/validations/measurement";
 
 const DATABASE_URL = process.env.DATABASE_URL;
 if (!DATABASE_URL) {
@@ -55,13 +56,20 @@ function randomWalk(
   target: number,
   days: number,
   volatility: number,
+  // Optional physiological band. A free walk can drift below the floor and
+  // mint an out-of-range row (a systolic-0 BP reading was observed in a
+  // fresh seed — iOS #33); clamping every step keeps the series inside the
+  // same band the input validator enforces.
+  clamp?: { min: number; max: number },
 ): number[] {
   const values: number[] = [start];
   for (let i = 1; i < days; i++) {
     const prev = values[i - 1];
     const drift = (target - prev) * 0.03; // mean reversion
     const noise = (Math.random() - 0.5) * volatility;
-    values.push(Math.round((prev + drift + noise) * 10) / 10);
+    let next = Math.round((prev + drift + noise) * 10) / 10;
+    if (clamp) next = Math.min(clamp.max, Math.max(clamp.min, next));
+    values.push(next);
   }
   return values;
 }
@@ -124,10 +132,10 @@ async function seed() {
 
     // Weight: 86.5 → trending down to ~82.5
     const weights = randomWalk(86.5, 82.0, days, 0.6);
-    // Systolic BP: 132 → improving to ~124
-    const sysBP = randomWalk(132, 124, days, 4);
-    // Diastolic BP: 85 → improving to ~78
-    const diaBP = randomWalk(85, 78, days, 3);
+    // Systolic BP: 132 → improving to ~124 (clamped to the physiological band)
+    const sysBP = randomWalk(132, 124, days, 4, VALUE_RANGES.BLOOD_PRESSURE_SYS);
+    // Diastolic BP: 85 → improving to ~78 (clamped to the physiological band)
+    const diaBP = randomWalk(85, 78, days, 3, VALUE_RANGES.BLOOD_PRESSURE_DIA);
     // Pulse: 72 → slight improvement to ~68
     const pulse = randomWalk(72, 68, days, 3);
     // Body fat: 24.5% → trending to ~22%
diff --git a/src/app/api/measurements/series/route.ts b/src/app/api/measurements/series/route.ts
index 916f9a82e..e782360e0 100644
--- a/src/app/api/measurements/series/route.ts
+++ b/src/app/api/measurements/series/route.ts
@@ -23,6 +23,7 @@ import { summarize, type DataPoint } from "@/lib/analytics/trends";
 import { redactSensitiveFields } from "@/lib/observability/redact-payload";
 import type { MeasurementType, SleepStage } from "@/generated/prisma/client";
 import { reconstructSleepNights } from "@/lib/analytics/sleep-night";
+import { VALUE_RANGES } from "@/lib/validations/measurement";
 import { loadUserSourcePriority } from "@/lib/rollups/measurement-read";
 import { resolveUserTimezone } from "@/lib/tz/resolver";
 import { convertGlucose, resolveGlucoseUnit } from "@/lib/glucose";
@@ -264,6 +265,12 @@ export const GET = apiHandler(async (request: NextRequest) => {
         };
       });
   } else if (kind === "bloodPressure") {
+    // Exclude non-physiological rows (systolic < 40 / diastolic < 20) from the
+    // series AND the implicit "latest" (the last point). BP is two rows paired
+    // client-side, so a corrupt row that slipped in before the input floor was
+    // enforced — a seed-era systolic-0, iOS #33 — must never surface as the
+    // latest reading. Floors mirror VALUE_RANGES (the input validator's min);
+    // this is a read-side selection guard, not a tightening of the write floor.
     const [sys, dia] = await Promise.all([
       prisma.measurement.findMany({
         where: {
@@ -271,6 +278,7 @@ export const GET = apiHandler(async (request: NextRequest) => {
           type: "BLOOD_PRESSURE_SYS",
           measuredAt: { gte: since },
           deletedAt: null,
+          value: { gte: VALUE_RANGES.BLOOD_PRESSURE_SYS.min },
         },
         orderBy: { measuredAt: "asc" },
         select: { id: true, value: true, measuredAt: true },
@@ -281,6 +289,7 @@ export const GET = apiHandler(async (request: NextRequest) => {
           type: "BLOOD_PRESSURE_DIA",
           measuredAt: { gte: since },
           deletedAt: null,
+          value: { gte: VALUE_RANGES.BLOOD_PRESSURE_DIA.min },
         },
         orderBy: { measuredAt: "asc" },
         select: { id: true, value: true, measuredAt: true },
diff --git a/src/lib/validations/measurement.ts b/src/lib/validations/measurement.ts
index 1e39e7cd5..ce3dc4574 100644
--- a/src/lib/validations/measurement.ts
+++ b/src/lib/validations/measurement.ts
@@ -343,7 +343,7 @@ export function getUnitForType(type: string): string {
 }
 
 // Plausible ranges per measurement type
-const VALUE_RANGES: Record<string, { min: number; max: number }> = {
+export const VALUE_RANGES: Record<string, { min: number; max: number }> = {
   WEIGHT: { min: 1, max: 500 },
   BLOOD_PRESSURE_SYS: { min: 40, max: 300 },
   BLOOD_PRESSURE_DIA: { min: 20, max: 200 },