diff --git a/docs/api/openapi.yaml b/docs/api/openapi.yaml
index 4e702ad03..611091141 100644
--- a/docs/api/openapi.yaml
+++ b/docs/api/openapi.yaml
@@ -71078,8 +71078,10 @@ components:
           anyOf:
             - type: string
             - type: "null"
-          description: Explicit unit token, set only on the `sleep` card (`h`, because its value is a per-night total in hours
-            rather than the canonical SLEEP_DURATION minutes). Null on every other kind.
+          description: "Explicit unit token. When set it wins over `unitKey`. Set on the `sleep` card (`h`, because its value is a
+            per-night total in hours rather than the canonical SLEEP_DURATION minutes) and, since v1.40.0, on the
+            `glucose` card: the record owner's glucose unit (`mg/dL` or `mmol/L`), with `latestValue`, `secondaryValue`
+            and `sparkline` converted to it (mmol/L to one decimal). Null on every other kind."
         sleepStages:
           anyOf:
             - type: object
diff --git a/src/app/api/dashboard/summary/__tests__/route.test.ts b/src/app/api/dashboard/summary/__tests__/route.test.ts
index e61286e5b..b1c5dc30e 100644
--- a/src/app/api/dashboard/summary/__tests__/route.test.ts
+++ b/src/app/api/dashboard/summary/__tests__/route.test.ts
@@ -561,6 +561,32 @@ describe("GET /api/dashboard/summary", () => {
     expect(glucose?.lastSeenAt).toBe(tenDaysAgo.toISOString());
   });
 
+  it("names the owner's glucose unit on the glucose card", async () => {
+    // Applied after the summary cache: the unit is the record's own choice
+    // and the card's numbers are in it (the conversion is pinned in
+    // `src/lib/dashboard/__tests__/glucose-card.test.ts`).
+    vi.mocked(getSession).mockResolvedValue({
+      ...SESSION_OK,
+      user: { ...SESSION_OK.user, glucoseUnit: "mmol/L" },
+    } as never);
+    vi.mocked(prisma.measurement.groupBy).mockResolvedValue([
+      {
+        type: "BLOOD_GLUCOSE",
+        _count: { _all: 4 },
+        _max: { measuredAt: new Date(Date.now() - 10 * 86_400_000) },
+      },
+    ] as never);
+    const res = await callGet(makeReq());
+    const body = (await res.json()) as {
+      data: { metrics: Array<{ id: string; unit: string | null }> };
+    };
+    expect(body.data.metrics.find((m) => m.id === "glucose")?.unit).toBe(
+      "mmol/L",
+    );
+    // Every other card keeps its own unit contract.
+    expect(body.data.metrics.find((m) => m.id === "weight")?.unit).toBeNull();
+  });
+
   it("emits the sleep tile as the night TIME-ASLEEP total in hours, not one stage (v1.11.4)", async () => {
     // SLEEP_DURATION is stored one row per STAGE per night (minutes). The
     // tile must SUM the asleep stages of the latest night and convert to
diff --git a/src/app/api/dashboard/summary/route.ts b/src/app/api/dashboard/summary/route.ts
index 26d76552f..40d0f9994 100644
--- a/src/app/api/dashboard/summary/route.ts
+++ b/src/app/api/dashboard/summary/route.ts
@@ -75,6 +75,8 @@ import {
 } from "@/lib/dashboard/summary-reads";
 import { resolveModuleMap } from "@/lib/modules/gate";
 import { gateMetricCardsByModules } from "@/lib/dashboard/widget-modules";
+import { glucoseCardInDisplayUnit } from "@/lib/dashboard/glucose-card";
+import { resolveGlucoseUnit } from "@/lib/glucose";
 import {
   summarizeSleepNights,
   reconstructSleepNights,
@@ -144,6 +146,9 @@ interface MetricCard {
    * `latestValue` is a per-NIGHT total expressed in HOURS (a float),
    * not the canonical `SLEEP_DURATION` minutes — see the sleep block
    * below for why the night total replaced the single-stage value.
+   * v1.40.0 — the `glucose` tile sets it to the owner's glucose unit
+   * (`"mg/dL"` or `"mmol/L"`), with its values converted to match
+   * (`glucoseCardInDisplayUnit`, applied after the cache read).
    */
   unit: string | null;
   /**
@@ -325,7 +330,10 @@ export const GET = apiHandler(async () => {
   // it off. Filtering the cached body makes the toggle effective on the very
   // next request.
   const modules = await resolveModuleMap(user.id);
-  const metrics = gateMetricCardsByModules(body.metrics, modules);
+  const glucoseUnit = resolveGlucoseUnit(user.glucoseUnit);
+  const metrics = gateMetricCardsByModules(body.metrics, modules).map((card) =>
+    glucoseCardInDisplayUnit(card, glucoseUnit),
+  );
   annotate({
     meta: {
       metrics_emitted: metrics.length,
diff --git a/src/lib/dashboard/__tests__/glucose-card.test.ts b/src/lib/dashboard/__tests__/glucose-card.test.ts
new file mode 100644
index 000000000..1257e2f64
--- /dev/null
+++ b/src/lib/dashboard/__tests__/glucose-card.test.ts
@@ -0,0 +1,47 @@
+import { describe, expect, it } from "vitest";
+
+import { glucoseCardInDisplayUnit } from "../glucose-card";
+
+const card = (over: Record<string, unknown> = {}) => ({
+  kind: "glucose",
+  latestValue: 101 as number | null,
+  secondaryValue: null as number | null,
+  sparkline: [90, 101, 126],
+  unit: null as string | null,
+  unitKey: "dashboard.metric.unit.glucose",
+  ...over,
+});
+
+describe("glucoseCardInDisplayUnit", () => {
+  it("converts the card to mmol/L and names the unit", () => {
+    expect(glucoseCardInDisplayUnit(card(), "mmol/L")).toMatchObject({
+      latestValue: 5.6,
+      secondaryValue: null,
+      sparkline: [5, 5.6, 7],
+      unit: "mmol/L",
+      unitKey: "dashboard.metric.unit.glucose",
+    });
+  });
+
+  it("keeps mg/dL values and names that unit too", () => {
+    expect(glucoseCardInDisplayUnit(card(), "mg/dL")).toMatchObject({
+      latestValue: 101,
+      sparkline: [90, 101, 126],
+      unit: "mg/dL",
+    });
+  });
+
+  it("leaves an empty card empty", () => {
+    expect(
+      glucoseCardInDisplayUnit(
+        card({ latestValue: null, sparkline: [] }),
+        "mmol/L",
+      ),
+    ).toMatchObject({ latestValue: null, sparkline: [], unit: "mmol/L" });
+  });
+
+  it("passes every other card through untouched", () => {
+    const weight = card({ kind: "weight", latestValue: 80 });
+    expect(glucoseCardInDisplayUnit(weight, "mmol/L")).toBe(weight);
+  });
+});
diff --git a/src/lib/dashboard/glucose-card.ts b/src/lib/dashboard/glucose-card.ts
new file mode 100644
index 000000000..e8ca5ab2b
--- /dev/null
+++ b/src/lib/dashboard/glucose-card.ts
@@ -0,0 +1,39 @@
+import { convertGlucose, type GlucoseUnit } from "@/lib/glucose";
+
+/** The fields of a dashboard summary card the glucose unit touches. */
+interface GlucoseConvertibleCard {
+  kind: string;
+  latestValue: number | null;
+  secondaryValue: number | null;
+  sparkline: number[];
+  unit: string | null;
+}
+
+/**
+ * Put the glucose card in the record owner's display unit.
+ *
+ * Glucose is stored in mg/dL. The summary card used to send that number with
+ * `unit: null` and a `unitKey` that reads "mg/dL", so a reader who chose
+ * mmol/L was shown 101 "mg/dL" on a client that honours the card. The card now
+ * carries its value, its secondary value and its sparkline in the chosen unit
+ * and names that unit in `unit`, the field that wins over `unitKey` (as the
+ * sleep card's `"h"` already does). Every other card passes through untouched.
+ *
+ * Applied after the summary cache is read, so changing the unit takes effect
+ * on the next request rather than after the cache window.
+ */
+export function glucoseCardInDisplayUnit<T extends GlucoseConvertibleCard>(
+  card: T,
+  unit: GlucoseUnit,
+): T {
+  if (card.kind !== "glucose") return card;
+  const show = (value: number | null) =>
+    value === null ? null : convertGlucose(value, unit);
+  return {
+    ...card,
+    latestValue: show(card.latestValue),
+    secondaryValue: show(card.secondaryValue),
+    sparkline: card.sparkline.map((value) => convertGlucose(value, unit)),
+    unit,
+  };
+}
diff --git a/src/lib/openapi/routes/dashboard.ts b/src/lib/openapi/routes/dashboard.ts
index 2779f7448..b006ee658 100644
--- a/src/lib/openapi/routes/dashboard.ts
+++ b/src/lib/openapi/routes/dashboard.ts
@@ -186,7 +186,7 @@ const dashboardMetricCard = z
       .string()
       .nullable()
       .describe(
-        "Explicit unit token, set only on the `sleep` card (`h`, because its value is a per-night total in hours rather than the canonical SLEEP_DURATION minutes). Null on every other kind.",
+        "Explicit unit token. When set it wins over `unitKey`. Set on the `sleep` card (`h`, because its value is a per-night total in hours rather than the canonical SLEEP_DURATION minutes) and, since v1.40.0, on the `glucose` card: the record owner's glucose unit (`mg/dL` or `mmol/L`), with `latestValue`, `secondaryValue` and `sparkline` converted to it (mmol/L to one decimal). Null on every other kind.",
       ),
     sleepStages: z
       .record(z.string(), z.number())