If you bill glucose monitors and diabetic testing supplies to Medicare, the KS and KX modifiers decide how a claim is classified. They look similar but mean opposite things about the patient, and getting them backwards is an easy way to create a denial. This guide explains what each one means and how they relate to quantity limits.
Last reviewed: October 2026. The policy documents cited below are revised periodically; check the current version before billing.
KS vs. KX in one table
| Modifier | Meaning on glucose monitor claims | Use for |
|---|---|---|
| KX | Insulin-treated beneficiary (requirements specified in the medical policy have been met) | Patients who are treated with insulin |
| KS | Glucose monitor supply for diabetic beneficiary not treated with insulin | Patients who are not treated with insulin |
Key point: in this policy, KX is an insulin-status flag, not an “exceeds the quantity limit” flag. Use KX if the patient is insulin treated and KS if the patient is not.
Which claims need one of them
According to Noridian’s guidance, one of these modifiers is required on every claim for glucose monitors, related supplies, continuous glucose monitors and supply allowances. The guidance lists the monitor codes E0607, E2100 and E2101, the continuous glucose monitor codes E2102 and E2103, and the supply allowance codes A4238 and A4239, along with the related test strips and lancets. KS goes on the monitor code and on each related supply on each claim. The same Noridian article also covers the CG and KF modifiers used with these products.
Do not report KX for a beneficiary who is treated exclusively with oral hypoglycemic agents. That patient is non-insulin treated, so KS is the correct modifier.
Quantity limits
Once the basic coverage criteria are met (a diabetes diagnosis, and the practitioner concludes that the patient or caregiver is trained to use the device), the Local Coverage Determination for glucose monitors (L33822) sets these amounts per three months:
- Not treated with insulin: up to 100 test strips and 100 lancets.
- Treated with insulin: up to 300 test strips and 300 lancets.
Billing above the limits
Claims above those amounts are denied unless all of the following are met:
- The basic coverage criteria are met.
- The treating practitioner had an in-person or Medicare-approved telehealth visit within the six months before ordering the excess quantity, evaluating diabetes control and the need for the quantity.
- Every six months the practitioner verifies that the patient is actually using the supplies as ordered before further supplies are dispensed.
On request, suppliers are expected to produce the standard written order, beneficiary authorization, proof of delivery, evidence of continued need and use, the meter on file, and the practitioner’s records.
Tip: track each patient’s insulin status in the billing record and re-confirm it at every reorder. A change in treatment changes both the modifier and the quantity limit.
Other test strip billing points
- One unit of A4253 equals 50 strips, so check unit conversion when ordering by box. Do not use A4253 for visual-reading strips that are not used in a glucose monitor.
- Only one spring-powered lancet device (A4258) is covered per six months.
- Test strip claims that overlap an inpatient or skilled nursing facility stay are denied.
- A missing diabetes diagnosis code is a common reason test strip claims are denied, according to CMS compliance guidance.
Related guides
- KX Modifier Explained: When to Use It and When Not To
- DME Billing Modifiers: NU, RR, KX, GA/GZ, KH/KI/KJ Guide
- NU, UE and RR Modifiers: Meaning and When to Use Each
- ABN Forms Explained
- Free denial code lookup
Sources
- Noridian, KS modifier: noridianmedicare.com
- Noridian, glucose monitor modifiers CG, KF, KS and KX (updated December 2024): noridianmedicare.com
- LCD L33822, Glucose Monitors (revision effective October 1, 2024): cms.gov
- Policy Article A52464, Glucose Monitors Policy Article: cms.gov
- CMS MLN compliance tips, glucose monitoring supplies: cms.gov
This article is educational and is not legal or coding advice. Always confirm current rules with your DME MAC and the Medicare Coverage Database.