diff --git a/src/components/targets/__tests__/range-bar.test.tsx b/src/components/targets/__tests__/range-bar.test.tsx
index bb045a3a4..2f4f2df3e 100644
--- a/src/components/targets/__tests__/range-bar.test.tsx
+++ b/src/components/targets/__tests__/range-bar.test.tsx
@@ -58,6 +58,19 @@ describe("<RangeBar>", () => {
     expect(html).toContain("var(--destructive)");
   });
 
+  it("keeps a lab outlier clear of the bar edge", () => {
+    const html = render({
+      value: 6.8,
+      min: 30,
+      max: 100,
+      unit: "ng/mL",
+      compact: true,
+      tone: "lab",
+    });
+
+    expect(html).not.toContain("left: 4%");
+  });
+
   it("makes the marker focusable with a text alternative for the value + range (2026-07-17 a11y audit M1)", () => {
     const html = render({
       value: 72,
diff --git a/src/components/targets/range-bar.tsx b/src/components/targets/range-bar.tsx
index d7b776a5b..a4a992117 100644
--- a/src/components/targets/range-bar.tsx
+++ b/src/components/targets/range-bar.tsx
@@ -54,6 +54,8 @@ export function RangeBar({
   const effectiveOrangeMax =
     orangeMax != null ? Math.max(orangeMax, max) : computedOrangeMax;
 
+  // Keep zero-width ranges from producing invalid percentages. The lab
+  // adapter currently avoids this by adding a synthetic bound when needed.
   const orangeSpan = Math.max(
     isLab ? Number.EPSILON : 1,
     effectiveOrangeMax - effectiveOrangeMin,
@@ -67,7 +69,11 @@ export function RangeBar({
   // Lab values can sit far outside a narrow reference window (for example
   // vitamin D at 6.8 against a minimum of 30). Expand the visible scale to
   // include the actual value instead of pinning its marker to the edge.
-  const outlierPadding = Math.max(span * 0.06, Number.EPSILON);
+  const baseVisualSpan = Math.max(
+    baseVisualMax - baseVisualMin,
+    Number.EPSILON,
+  );
+  const outlierPadding = Math.max(baseVisualSpan * 0.06, Number.EPSILON);
   const visualMin = isLab
     ? Math.min(baseVisualMin, value - outlierPadding)
     : baseVisualMin;