fix(glucose): state band edges in the reader's glucose unit

The time-in-range labels in the doctor report, the target caption on
the glucose panel, the glucose page description and the fasting
explainer printed fixed mg/dL figures, so a reader on mmol/L saw
"Low (< 70 mg/dL)" beside values in mmol/L.

The cut-points now live in one place (`GLUCOSE_TIR_CUT_POINTS`,
`GLUCOSE_FASTING_CUT_POINTS`) with the SI figure each guideline prints,
the analytics engine counts its bands from the same constants, and
every sentence takes the band edges and unit as parameters through
`glucoseBandParams`, formatted with the reader's number format.

The unit-preference guard now also reads the locale bundles: a string
that names mg/dL or mmol/L fails unless it is allowlisted with a
reason.

Refs #1067

src/__tests__/unit-preference-display-guard.test.ts

@@ -10,7 +10,7 @@
  *
  * Mutation check: add `unit="kg"` back to any swept page and this goes red.
  */
-import { readFileSync } from "node:fs";
+import { readdirSync, readFileSync } from "node:fs";
 import { join } from "node:path";
 
 import { stripComments, walkSourceFiles } from "./helpers/source-files";
@@ -515,3 +515,74 @@ describe("unit-preference display guard — AI and Coach producers", () => {
     expect(offenders).toEqual([]);
   });
 });
+
+/**
+ * Locale strings that may name a glucose unit literally, each with the reason
+ * it is not a reading shown in the reader's unit. Keys are dotted paths and
+ * apply to every locale bundle.
+ */
+const GLUCOSE_UNIT_LITERAL_ALLOWLIST: Record<string, string> = {
+  "dashboard.metric.unit.glucose":
+    "the unit token the dashboard summary wire hands the native client; the web resolves the glucose unit from the account instead",
+  "labs.biomarker.form.unitPlaceholder":
+    "an example of a free-text lab unit in an input placeholder, not a reading",
+};
+
+const GLUCOSE_UNIT_LITERAL = /mg\/dl|mmol\/l\b/i;
+
+function flattenStrings(
+  node: unknown,
+  path: string,
+  out: Array<[string, string]>,
+): void {
+  if (typeof node === "string") {
+    out.push([path, node]);
+  } else if (node && typeof node === "object") {
+    for (const [key, value] of Object.entries(node)) {
+      flattenStrings(value, path ? `${path}.${key}` : key, out);
+    }
+  }
+}
+
+describe("unit-preference display guard — locale strings", () => {
+  const MESSAGES = join(process.cwd(), "messages");
+  const bundles = readdirSync(MESSAGES).filter((f) => f.endsWith(".json"));
+
+  it("reads every locale bundle", () => {
+    expect(bundles.length).toBeGreaterThanOrEqual(7);
+  });
+
+  it("no locale string fixes a glucose unit outside the allowlist", () => {
+    // A sentence that prints "70–180 mg/dL" shows mg/dL to a reader who
+    // chose mmol/L. Band and unit go in as parameters (`glucoseBandParams`).
+    const offenders: string[] = [];
+    for (const file of bundles) {
+      const entries: Array<[string, string]> = [];
+      flattenStrings(
+        JSON.parse(readFileSync(join(MESSAGES, file), "utf8")),
+        "",
+        entries,
+      );
+      for (const [key, value] of entries) {
+        if (key in GLUCOSE_UNIT_LITERAL_ALLOWLIST) continue;
+        if (GLUCOSE_UNIT_LITERAL.test(value)) offenders.push(`${file}: ${key}`);
+      }
+    }
+    expect(offenders).toEqual([]);
+  });
+
+  it("every allowlisted key still exists and still names a unit", () => {
+    // An entry whose string was reworded or removed is a stale exemption.
+    const en: Array<[string, string]> = [];
+    flattenStrings(
+      JSON.parse(readFileSync(join(MESSAGES, "en.json"), "utf8")),
+      "",
+      en,
+    );
+    const byKey = new Map(en);
+    const stale = Object.keys(GLUCOSE_UNIT_LITERAL_ALLOWLIST).filter(
+      (key) => !GLUCOSE_UNIT_LITERAL.test(byKey.get(key) ?? ""),
+    );
+    expect(stale).toEqual([]);
+  });
+});

src/app/insights/blood-glucose/page.tsx

@@ -5,8 +5,12 @@ import { Droplet } from "lucide-react";
 import { HealthKitMetricPage } from "@/components/insights/healthkit-metric-page";
 import { GlucoseClinicalPanel } from "@/components/insights/glucose/glucose-clinical-panel";
 import { useAuth } from "@/hooks/use-auth";
-import { useTranslations } from "@/lib/i18n/context";
-import { MGDL_PER_MMOL, resolveGlucoseUnit } from "@/lib/glucose";
+import { useFormatters, useTranslations } from "@/lib/i18n/context";
+import {
+  glucoseBandParams,
+  MGDL_PER_MMOL,
+  resolveGlucoseUnit,
+} from "@/lib/glucose";
 
 /**
  * v1.7.0 — `/insights/blood-glucose`.
@@ -27,6 +31,7 @@ import { MGDL_PER_MMOL, resolveGlucoseUnit } from "@/lib/glucose";
 export default function InsightsBlutzuckerPage() {
   const { user } = useAuth();
   const { t } = useTranslations();
+  const fmt = useFormatters();
   const glucoseUnit = resolveGlucoseUnit(user?.glucoseUnit ?? null);
   const isMmol = glucoseUnit === "mmol/L";
 
@@ -38,6 +43,9 @@ export default function InsightsBlutzuckerPage() {
       chartKey="bloodGlucose"
       i18nPrefix="insights.bloodGlucose"
       explainerMetric="bloodGlucose"
+      // The definition names the fasting cut-points; they follow the
+      // reader's glucose unit like the chart does.
+      explainerParams={glucoseBandParams(glucoseUnit, fmt.number)}
       color="var(--chart-3)"
       unit={glucoseUnit}
       yAxisUnit={glucoseUnit}

src/components/insights/__tests__/sub-page-shell.test.tsx

@@ -2,6 +2,8 @@ import { describe, it, expect, vi } from "vitest";
 import { renderToStaticMarkup } from "react-dom/server";
 
 import { I18nProvider } from "@/lib/i18n/context";
+import { glucoseBandParams } from "@/lib/glucose";
+import { makeFormatters } from "@/lib/format-locale";
 import { SubPageShell } from "../sub-page-shell";
 
 vi.mock("next/navigation", () => ({
@@ -68,6 +70,27 @@ describe("<SubPageShell>", () => {
     );
   });
 
+  it("fills the explainer's figures from the explainer parameters", () => {
+    // The glucose definition names the fasting cut-points; a reader on
+    // mmol/L reads them in mmol/L, never a fixed "100 mg/dL".
+    const html = render(
+      <SubPageShell
+        title="Blood glucose"
+        explainerMetric="bloodGlucose"
+        explainerParams={glucoseBandParams(
+          "mmol/L",
+          makeFormatters("en", "UTC", "AUTO", "AUTO").number,
+        )}
+      >
+        <span />
+      </SubPageShell>,
+    );
+    expect(html).toContain(
+      "a fasting reading under 5.6 mmol/L is normal, 5.6–6.9 is prediabetes, and 7.0 or above",
+    );
+    expect(html).not.toContain("{");
+  });
+
   it("no longer paints the round `?` explainer trigger next to the heading", () => {
     const html = render(
       <SubPageShell title="Blood pressure" explainerMetric="bloodPressure">

src/components/insights/glucose/__tests__/glucose-clinical-panel.test.tsx

@@ -148,6 +148,30 @@ describe("<GlucoseClinicalPanel> asserted state", () => {
     expect(html).toContain("J-index");
   });
 
+  it("states the target band in the reader's unit and number format", () => {
+    // The caption used to print "70–180 mg/dL" to every reader, beside
+    // values the panel had already converted to mmol/L.
+    authMock.mockReturnValue({
+      user: { glucoseUnit: "mmol/L" },
+      isAuthenticated: true,
+    });
+    analyticsMock.mockReturnValue({
+      isLoading: false,
+      data: { glucoseClinical: assertedClinical(), glucoseByContext: {} },
+    });
+    const de = render(<GlucoseClinicalPanel />, "de");
+    expect(de).toContain("(3,9–10,0 mmol/L ist das Ziel)");
+    expect(de).not.toMatch(/mg\/dl/i);
+
+    authMock.mockReturnValue({
+      user: { glucoseUnit: "mg/dL" },
+      isAuthenticated: true,
+    });
+    expect(render(<GlucoseClinicalPanel />)).toContain(
+      "(70–180 mg/dL is the target)",
+    );
+  });
+
   it("flags the CV badge unstable at CV% >= 36", () => {
     // wide spread → CV well above 36
     const values = Array.from({ length: 20 }, (_, i) =>

src/components/insights/glucose/glucose-clinical-panel.tsx

@@ -12,8 +12,12 @@ import { LearnMoreLink } from "@/components/ui/learn-more-link";
 import { Skeleton } from "@/components/ui/skeleton";
 import { useAuth } from "@/hooks/use-auth";
 import { useAnalyticsQuery } from "@/lib/queries/use-analytics-query";
-import { useTranslations } from "@/lib/i18n/context";
-import { convertGlucose, resolveGlucoseUnit } from "@/lib/glucose";
+import { useFormatters, useTranslations } from "@/lib/i18n/context";
+import {
+  convertGlucose,
+  glucoseBandParams,
+  resolveGlucoseUnit,
+} from "@/lib/glucose";
 import type { DataSummary } from "@/lib/analytics/trends";
 import { GlucoseTirBar } from "./glucose-tir-bar";
 import { GlucoseAdvancedDisclosure } from "./glucose-advanced-disclosure";
@@ -41,6 +45,7 @@ import { GlucoseAdvancedDisclosure } from "./glucose-advanced-disclosure";
 export function GlucoseClinicalPanel() {
   const { user, isAuthenticated } = useAuth();
   const { t } = useTranslations();
+  const fmt = useFormatters();
   const query = useAnalyticsQuery({});
 
   const glucoseUnit = resolveGlucoseUnit(user?.glucoseUnit ?? null);
@@ -158,7 +163,10 @@ export function GlucoseClinicalPanel() {
             </div>
             <GlucoseTirBar distribution={dist} />
             <p className="text-muted-foreground text-xs">
-              {t("insights.bloodGlucose.clinical.tir.caption")}
+              {t(
+                "insights.bloodGlucose.clinical.tir.caption",
+                glucoseBandParams(glucoseUnit, fmt.number),
+              )}
             </p>
           </section>
         ) : null}

src/components/insights/healthkit-metric-page.tsx

@@ -153,6 +153,8 @@ export interface HealthKitMetricPageProps {
    * Resolves `insights.subPage.explainer.<explainerMetric>{Title,Body}`.
    */
   explainerMetric?: string;
+  /** Interpolation values for the explainer sentence (`SubPageShell`). */
+  explainerParams?: Record<string, string>;
   /**
    * v1.8.5 W5 — when set, renders `<MetricTargetSummary slug=…>` beneath
    * the chart. Used by blood glucose, whose per-context ADA / DDG bands
@@ -227,6 +229,7 @@ export function HealthKitMetricPage({
   coachPrefill,
   valueScale,
   explainerMetric,
+  explainerParams,
   targetSummarySlug,
   statusMetric,
   statIcon,
@@ -334,7 +337,10 @@ export function HealthKitMetricPage({
       : rawSummary;
 
   const title = t(`${i18nPrefix}.title`);
-  const description = t(`${i18nPrefix}.description`);
+  // A description that names its unit ("in mg/dL") reads the resolved one.
+  const description = t(`${i18nPrefix}.description`, {
+    unit: resolvedUnit ?? "",
+  });
 
   // v1.12.7 — in-flight skeleton. The page consumed only `{data, isEmpty}`
   // before, so the ~30 HealthKit sub-pages painted nothing until the
@@ -347,6 +353,7 @@ export function HealthKitMetricPage({
         title={title}
         description={description}
         explainerMetric={explainerMetric}
+        explainerParams={explainerParams}
         statStrip={<StatStripSkeleton />}
       >
         <ChartSkeleton />
@@ -364,6 +371,7 @@ export function HealthKitMetricPage({
         title={title}
         description={description}
         explainerMetric={explainerMetric}
+        explainerParams={explainerParams}
       >
         <QueryErrorRow
           slot="healthkit-metric-error"
@@ -389,6 +397,7 @@ export function HealthKitMetricPage({
         title={title}
         description={description}
         explainerMetric={explainerMetric}
+        explainerParams={explainerParams}
       >
         <MetricEmptyState
           icon={emptyStateIcon}
@@ -406,6 +415,7 @@ export function HealthKitMetricPage({
       title={title}
       description={description}
       explainerMetric={explainerMetric}
+      explainerParams={explainerParams}
       statStrip={
         <MetricStatStrip
           summary={summary}

src/components/insights/sub-page-shell.tsx

@@ -70,6 +70,11 @@ export interface SubPageShellProps {
    * one- to two-sentence definition, no tap required.
    */
   explainerMetric?: string;
+  /**
+   * Interpolation values for the explainer sentence, for a definition that
+   * names figures in the reader's own unit (the glucose cut-points).
+   */
+  explainerParams?: Record<string, string>;
   /**
    * v1.4.27 MB7 / CF-35 — opt-in programmatic focus on mount.
    *
@@ -155,6 +160,7 @@ export function SubPageShell({
   badge,
   description,
   explainerMetric,
+  explainerParams,
   focusOnMount = false,
   statStrip,
   coachReadStrip,
@@ -385,7 +391,10 @@ export function SubPageShell({
               data-slot="metric-explainer-inline"
               className="text-foreground text-sm leading-relaxed"
             >
-              {t(`insights.subPage.explainer.${explainerMetric}Body`)}
+              {t(
+                `insights.subPage.explainer.${explainerMetric}Body`,
+                explainerParams,
+              )}
             </p>
           ) : null}
           {description && !explainerMetric ? (

src/lib/__tests__/doctor-report-pdf-core.test.ts

@@ -594,6 +594,30 @@ describe("doctor-report clinical glucose panel", () => {
     expect(text).toContain("Glucose Management Indicator");
   });
 
+  it("labels the time-in-range bands in the owner's glucose unit", async () => {
+    // The band labels used to read "Low (< 70 mg/dL)" in a report whose
+    // values were all in mmol/L.
+    const data = makeData({
+      glucoseUnit: "mmol/L",
+      glucoseClinical: computeGlucoseClinicalMetrics(denseReadings(), {
+        now: FIXED_NOW,
+        windowDays: 90,
+      }),
+    });
+    const bytes = renderDoctorReportPdfBytes(data, {
+      timeFormat: "AUTO",
+      dateFormat: "AUTO",
+      t: getServerTranslator("de").t,
+      locale: "de",
+      now: FIXED_NOW,
+    });
+    const text = await extractText(bytes);
+    expect(text).toContain("Zeit im Zielbereich (3,9–10,0 mmol/L)");
+    expect(text).toContain("Sehr niedrig (< 3,0 mmol/L)");
+    expect(text).toContain("Sehr hoch (> 13,9 mmol/L)");
+    expect(text).not.toMatch(/mg\/dl/i);
+  });
+
   it("omits the clinical panel when there are no glucose readings", async () => {
     const data = makeData(); // empty (zero-reading) glucose panel
     const bytes = renderDoctorReportPdfBytes(data, {

src/lib/__tests__/glucose.test.ts

@@ -9,7 +9,11 @@ import {
   glucoseContextBucket,
   groupByGlucoseContext,
   GLUCOSE_CONTEXT_UNSPECIFIED,
+  GLUCOSE_FASTING_CUT_POINTS,
+  GLUCOSE_TIR_CUT_POINTS,
+  glucoseBandParams,
 } from "../glucose";
+import { makeFormatters } from "../format-locale";
 
 describe("glucose conversion", () => {
   it("converts mg/dL to mmol/L with 1 decimal", () => {
@@ -157,3 +161,45 @@ describe("glucose context buckets (#943)", () => {
     );
   });
 });
+
+describe("glucose band parameters", () => {
+  const de = makeFormatters("de", "UTC", "AUTO", "AUTO").number;
+  const en = makeFormatters("en", "UTC", "AUTO", "AUTO").number;
+
+  it("states the consensus bands in mg/dL as whole numbers", () => {
+    expect(glucoseBandParams("mg/dL", en)).toMatchObject({
+      unit: "mg/dL",
+      veryLow: "54",
+      low: "70",
+      high: "180",
+      veryHigh: "250",
+      prediabetesFrom: "100",
+      prediabetesTo: "125",
+      diabetesFrom: "126",
+    });
+  });
+
+  it("states them in mmol/L with the locale's decimal separator", () => {
+    expect(glucoseBandParams("mmol/L", de)).toMatchObject({
+      unit: "mmol/L",
+      veryLow: "3,0",
+      low: "3,9",
+      high: "10,0",
+      veryHigh: "13,9",
+      prediabetesFrom: "5,6",
+      prediabetesTo: "6,9",
+      diabetesFrom: "7,0",
+    });
+  });
+
+  it("carries SI figures that agree with the conversion", () => {
+    // The consensus bands convert exactly; the ADA cut-points are within
+    // one rounding step of it (100 mg/dL is printed as 5.6, converts to 5.5).
+    for (const point of Object.values(GLUCOSE_TIR_CUT_POINTS)) {
+      expect(point.mmol).toBe(mgdlToMmol(point.mgdl));
+    }
+    for (const point of Object.values(GLUCOSE_FASTING_CUT_POINTS)) {
+      expect(Math.abs(point.mmol - point.mgdl / 18.0182)).toBeLessThan(0.1);
+    }
+  });
+});

src/lib/analytics/glucose-metrics.ts

@@ -39,6 +39,8 @@
  *     Diabetes Care 29(11):2433-2438, DOI 10.2337/dc06-1085.
  */
 
+import { GLUCOSE_TIR_CUT_POINTS } from "@/lib/glucose";
+
 // ── Inputs ───────────────────────────────────────────────
 
 /** A single spot blood-glucose reading. Value is canonical mg/dL. */
@@ -79,11 +81,13 @@ export interface GlucoseMetricsOptions {
 }
 
 // ── Consensus thresholds (Battelino 2019) ────────────────
-// Bands in mg/dL. These are consensus FACTS, cited above.
-const TBR_LEVEL2_MAX = 54; // very low: G < 54
-const TBR_LEVEL1_MAX = 70; // low: G < 70 (level-1 sub-band is 54–69)
-const TAR_LEVEL1_MIN = 180; // high: G > 180 (level-1 sub-band is 181–250)
-const TAR_LEVEL2_MIN = 250; // very high: G > 250
+// Bands in mg/dL. These are consensus FACTS, cited above. The values live in
+// `GLUCOSE_TIR_CUT_POINTS` so the band labels a reader sees and the bands
+// this engine counts are the same numbers.
+const TBR_LEVEL2_MAX = GLUCOSE_TIR_CUT_POINTS.veryLow.mgdl; // very low: G < 54
+const TBR_LEVEL1_MAX = GLUCOSE_TIR_CUT_POINTS.low.mgdl; // low: G < 70 (level-1 sub-band is 54–69)
+const TAR_LEVEL1_MIN = GLUCOSE_TIR_CUT_POINTS.high.mgdl; // high: G > 180 (level-1 sub-band is 181–250)
+const TAR_LEVEL2_MIN = GLUCOSE_TIR_CUT_POINTS.veryHigh.mgdl; // very high: G > 250
 // Time-in-range target band is [70, 180] inclusive.
 /** The time-in-range band, mg/dL, inclusive at both ends. */
 export const TIME_IN_RANGE_MGDL = {

src/lib/doctor-report-pdf/measurements-charts-section.ts

@@ -1,7 +1,11 @@
 import type { jsPDF } from "jspdf";
 import { GLUCOSE_CONTEXT_BUCKETS } from "@/lib/glucose";
 import autoTable from "jspdf-autotable";
-import { convertGlucose, resolveGlucoseUnit } from "../glucose";
+import {
+  convertGlucose,
+  glucoseBandParams,
+  resolveGlucoseUnit,
+} from "../glucose";
 import { reportStatValue } from "../doctor-report/stat-display";
 import type { MeasurementType } from "@/generated/prisma/client";
 import { MEASUREMENT_TYPE_LABEL_KEYS } from "../measurements/type-label-keys";
@@ -303,26 +307,29 @@ export function buildMeasurementsChartsSection(
   const clinical = data.glucoseClinical;
   if (clinical && clinical.readingCount > 0 && clinical.distribution) {
     const pct = (fraction: number) => `${num(fraction * 100)} %`;
+    // The band edges follow the reader's glucose unit, like every value in
+    // the table beside them.
+    const bands = glucoseBandParams(glucoseUnit, num);
     const clinicalRows: string[][] = [];
     const dist = clinical.distribution;
     clinicalRows.push([
-      t("doctorReport.glucoseClinical.tirInRange"),
+      t("doctorReport.glucoseClinical.tirInRange", bands),
       pct(dist.tir),
     ]);
     clinicalRows.push([
-      t("doctorReport.glucoseClinical.tirLow"),
+      t("doctorReport.glucoseClinical.tirLow", bands),
       pct(dist.tbrLevel1),
     ]);
     clinicalRows.push([
-      t("doctorReport.glucoseClinical.tirVeryLow"),
+      t("doctorReport.glucoseClinical.tirVeryLow", bands),
       pct(dist.tbrLevel2),
     ]);
     clinicalRows.push([
-      t("doctorReport.glucoseClinical.tirHigh"),
+      t("doctorReport.glucoseClinical.tirHigh", bands),
       pct(dist.tarLevel1),
     ]);
     clinicalRows.push([
-      t("doctorReport.glucoseClinical.tirVeryHigh"),
+      t("doctorReport.glucoseClinical.tirVeryHigh", bands),
       pct(dist.tarLevel2),
     ]);
     if (clinical.meanMgdl !== null) {

src/lib/glucose.ts

@@ -42,6 +42,59 @@ export function toCanonicalMgdl(value: number, from: GlucoseUnit): number {
   return from === "mmol/L" ? mmolToMgdl(value) : Math.round(value);
 }
 
+/**
+ * A published glucose cut-point, in both units as its source states it.
+ *
+ * The SI figure is carried rather than converted because a guideline prints
+ * its own rounding: ADA's fasting cut-point is 100 mg/dL and 5.6 mmol/L, and
+ * `mgdlToMmol(100)` gives 5.5. A reader on mmol/L must see the number their
+ * own guideline prints, not a re-rounded neighbour of it.
+ */
+export interface GlucoseCutPoint {
+  mgdl: number;
+  mmol: number;
+}
+
+/** Consensus time-in-range band edges (Battelino 2019). */
+export const GLUCOSE_TIR_CUT_POINTS = {
+  veryLow: { mgdl: 54, mmol: 3.0 },
+  low: { mgdl: 70, mmol: 3.9 },
+  high: { mgdl: 180, mmol: 10.0 },
+  veryHigh: { mgdl: 250, mmol: 13.9 },
+} as const satisfies Record<string, GlucoseCutPoint>;
+
+/** Fasting-glucose diagnostic cut-points for adults (ADA 2024). */
+export const GLUCOSE_FASTING_CUT_POINTS = {
+  prediabetesFrom: { mgdl: 100, mmol: 5.6 },
+  prediabetesTo: { mgdl: 125, mmol: 6.9 },
+  diabetesFrom: { mgdl: 126, mmol: 7.0 },
+} as const satisfies Record<string, GlucoseCutPoint>;
+
+/**
+ * The interpolation parameters every glucose band sentence takes: each
+ * cut-point in the reader's unit, formatted by the caller's locale-aware
+ * number formatter, plus the unit symbol. A sentence that names a band
+ * reads its numbers from here, so no locale string carries a fixed unit.
+ */
+export function glucoseBandParams(
+  unit: GlucoseUnit,
+  formatNumber: (value: number, fractionDigits: number) => string,
+): Record<string, string> {
+  const digits = unit === "mmol/L" ? 1 : 0;
+  const v = (point: GlucoseCutPoint) =>
+    formatNumber(unit === "mmol/L" ? point.mmol : point.mgdl, digits);
+  return {
+    unit,
+    veryLow: v(GLUCOSE_TIR_CUT_POINTS.veryLow),
+    low: v(GLUCOSE_TIR_CUT_POINTS.low),
+    high: v(GLUCOSE_TIR_CUT_POINTS.high),
+    veryHigh: v(GLUCOSE_TIR_CUT_POINTS.veryHigh),
+    prediabetesFrom: v(GLUCOSE_FASTING_CUT_POINTS.prediabetesFrom),
+    prediabetesTo: v(GLUCOSE_FASTING_CUT_POINTS.prediabetesTo),
+    diabetesFrom: v(GLUCOSE_FASTING_CUT_POINTS.diabetesFrom),
+  };
+}
+
 export function resolveGlucoseUnit(
   userPreference: string | null | undefined,
 ): GlucoseUnit {