A complete 2026 guide to the discontinuation of ASCP Route 3 — what it was, when and why it was retired, and the active routes that replace it for anyone trying to navigate MLS certification today.
ASCP Route 3 was discontinued on January 1, 2023. It was the eligibility route built specifically for holders of the now-retired Certified Laboratory Assistant (CLA) credential, which the ASCP itself stopped issuing back in 1982. With the CLA population shrinking to near-zero through natural attrition, ASCP retired the route. The same change applied to MLT Route 2 on the same date — it had the same CLA-based structure.
If you’ve encountered Route 3 in your research and are trying to figure out what to do now, the answer depends on your background. There are five other active routes to MLS certification, and at least one of them almost certainly applies to you. This guide walks through what Route 3 was, why it was retired, and exactly which active route you should pursue instead.
| If you held a valid CLA(ASCP) credential through 2022 Your fastest replacement path is ASCP Route 4 — bachelor’s degree + 16 biology / 16 chemistry coursework + 5 years clinical experience. If you also hold MLT certification, Route 2 is faster (only 2 years experience needed). Both routes accept the same prerequisite coursework, which can be completed online through regionally accredited programs in months rather than years. |
To understand why Route 3 was discontinued, you need a bit of historical context — and the history reveals a credential category that quietly faded out over four decades.
Per the official ASCP BOC history, the Certified Laboratory Assistant (CLA) credential was established in 1963 as the second generalist-level certification in clinical laboratory science. It replaced an older credential called the Laboratory Aide (LA), and was positioned as a mid-level qualification between phlebotomy/MLA-tier roles and the full MLT or MT (later MLS) credentials.
But the CLA had a short institutional life. By 1982, ASCP had discontinued the credential, replacing it functionally with the more rigorous MLT(ASCP) certification (which had been established in 1969). Anyone who earned a CLA before 1982 retained the credential — but no new CLA certifications were issued after that date.
ASCP Route 3 existed as a path for the dwindling population of working CLA holders to upgrade to MLS certification. Specifically, Route 3 required:
The structure was nearly identical to Route 4, with one key difference: Route 3 used the CLA credential as the gating criterion, while Route 4 (then and now) requires no prior credential beyond the bachelor’s degree and coursework.
By the early 2020s, ASCP recognized two realities about Route 3 and the parallel MLT Route 2:
On January 1, 2023, ASCP officially discontinued both MLS Route 3 and MLT Route 2. The discontinuation does not affect anyone who passed the MLS exam through Route 3 prior to 2023 — those credentials remain valid and active. It only means new applicants can no longer use this specific pathway to MLS or MLT certification.
The discontinuation directly affects a smaller group of people than the volume of search traffic on this topic might suggest. Most readers who land on this article fall into one of three categories — and the implications differ for each.
This is the only group that lost a previously available option. If you held a valid CLA(ASCP) credential through the end of 2022 and were planning to use Route 3 to upgrade to MLS, that specific path closed on January 1, 2023. The CLA credential itself remains valid for anyone who currently holds it — but it is no longer accepted as the gating credential for MLS Route 3 (or MLT Route 2).
Realistically, this is a small population. Anyone who earned a CLA in the program’s final year of issuance (1982) is now in their mid-60s or older. Many have retired. Some upgraded to MLT or MLS years ago. A few held the CLA continuously for decades while working in labs and were planning a late-career credential upgrade. For this last group, the next two sections offer concrete replacement paths.
A surprising amount of MLS exam-prep material online still references Route 3 as if it were active. If you’ve encountered Route 3 mentioned in a study guide, an academic advising document, a blog post from before 2023, or a Reddit thread referencing the old eligibility framework, you’ve likely landed on outdated information. Route 3 doesn’t apply to you simply because it doesn’t exist anymore — but the rest of the route framework (Routes 1, 2, 4, 5, and 6) still does.
The active route that applies to you depends on your background. Section 3 walks through the decision tree.
If you’re researching MLS certification for the first time and Route 3 came up as part of your overview reading, it does not affect your path because it would not have applied to you anyway — Route 3 only ever applied to CLA holders. Your active route is almost certainly Route 1 (NAACLS program), Route 2 (MLT-to-MLS bridge), or Route 4 (5-year experience pathway).
| Quick self-identification Were you ever issued a CLA(ASCP) certification (between 1963 and 1982)? → Yes — Section 3 applies directly to you. Skip ahead. → No — You’re researching the route framework. Section 4 has the broader “which route applies to me” guide. Route 3 was never going to be your path. |
For former CLA holders looking to upgrade to MLS now that Route 3 is closed, two active routes provide essentially the same destination — and at least one of them applies to almost everyone in this position.
Route 4 is the active pathway that most closely mirrors what Route 3 used to do. It does not require any prior ASCP credential — meaning it accepts you regardless of whether your CLA was current at retirement, has lapsed, or is still active. Per the official ASCP MLS credential page, Route 4 requires:
For someone who held a CLA and worked in clinical laboratories for decades, the 5-year experience requirement is generally the easiest piece — most former CLA holders accumulated far more than 5 years of qualifying experience over their careers. The bachelor’s degree and the 16+16 coursework are usually the bigger gaps.
If you upgraded from CLA to MLT(ASCP) at some point in your career — which many former CLA holders did when MLT was established as the replacement credential — Route 2 is a faster path than Route 4. Per the ASCP MLS Route 2 documentation, you need:
If your MLT(ASCP) credential is currently valid and you have at least 2 years of recent qualifying experience, Route 2 cuts your experience requirement in half compared to Route 4.
| Requirement | Route 2 (if you have MLT) | Route 4 (no prior credential needed) |
| Bachelor’s degree | Required (any field) | Required (any field) |
| 16+16 prerequisite coursework | Required | Required |
| Prior credential | Valid MLT(ASCP) required | Not required |
| Clinical experience | 2 years in last 5 | 5 years in last 10 |
| Application fee | $260 | $260 |
If both routes apply to you, choose Route 2 — the experience requirement is meaningfully easier to meet, especially if your active clinical work is concentrated in the last several years.
ASCP currently maintains five active routes to the MLS credential plus a discontinued sixth (Route 3). Here’s the complete map of what exists today, drawn directly from the official MLS credential page:
| Route | Who it’s for | Core requirements |
| Route 1 | Traditional MLS graduates | Bachelor’s + completion of a NAACLS-accredited MLS program in the last 5 years |
| Route 2 | MLT-to-MLS bridge applicants | Valid MLT(ASCP) + bachelor’s + 16+16 + 2 years clinical experience in last 5 |
| Route 3 | DISCONTINUED Jan 1, 2023 | Was for CLA(ASCP) holders. No longer available — see Routes 2, 4, or 6 instead. |
| Route 4 | Experienced lab professionals (no prior credential required) | Bachelor’s + 16+16 + 5 years clinical experience in last 10 |
| Route 5 | MLS(ASCPi) international transition | Valid MLS(ASCPi) + transcript evaluation + 5 years experience in last 10 |
| Route 6 | US military lab professionals | 50-week US military lab training course in last 10 years + bachelor’s + 16+16 + 1 year clinical experience |
If multiple routes apply, the one with the lighter clinical experience requirement is usually preferred. ASCP also offers a free Eligibility Assistant tool that walks you through the decision interactively.
All five active MLS routes — Routes 1, 2, 4, 5, and 6 — share the same 16+16 prerequisite coursework requirement. So whatever your replacement route, the prerequisite gap-closing work is identical to what someone using the discontinued Route 3 would have faced.
16 semester hours of biology including microbiology, and 16 semester hours of chemistry including organic chemistry or biochemistry. The full breakdown is covered in our complete guide to the ASCP 16+16 requirement, but here’s the short version of what most applicants need.
| Gap | Course to take | Why it matters |
| Missing microbiology | BIO 210 Microbiology w/ Lab | Required specialization within 16 biology hours |
| Missing organic or biochemistry | CHEM 330 Biochemistry I | Required specialization within 16 chemistry hours |
| Short on biology credits | BIO 270 A&P I BIO 275 A&P II | 8 credits toward 16-hour total |
| Short on chemistry credits | CHEM 151 Gen Chem I CHEM 152 Gen Chem II | 8 credits toward 16-hour total |
| Full prerequisite rebuild | Browse the full catalog | 8 courses cover the entire 16+16 requirement in 4–8 months |
If you earned your CLA in the late 1970s or 1981–1982, your original biology and chemistry coursework is now 40+ years old. Even if those courses appear on your transcript and would technically count toward the 16+16 ASCP requirement, individual NAACLS programs increasingly impose recency rules on prerequisite coursework — typically 5 to 10 years.
Route 4 itself does not impose a recency rule on the prerequisite coursework — only on the 5 years of clinical experience. So for ASCP exam eligibility purposes alone, you may technically qualify with old coursework. But if you are also applying to a NAACLS-accredited program for clinical training, the recency rule may still apply. Our pillar guide on refreshing an expired science degree walks through this distinction in detail.
| Self-paced online prerequisites are the fastest path Each course on PrereqCourses.com starts on the first of every month, is fully self-paced (typically 4–8 weeks per course), and is offered through Upper Iowa University — a regionally accredited (HLC) four-year institution. The official UIU transcript satisfies ASCP’s “regionally or nationally accredited college/university” requirement without exception, regardless of which active route you use. |
Yes. The discontinuation only affects new applications. MLS credentials earned through Route 3 prior to January 1, 2023 remain valid and active, subject to the standard ASCP Credential Maintenance Program (CMP) renewal requirements. You don’t need to re-apply or do anything different — just continue your normal CMP cycle.
Not exactly. The CLA credential itself was discontinued in 1982 — meaning ASCP stopped issuing new CLA certifications back then. If you held an active CLA after 1982, that credential remains valid (though not currently subject to renewal in the way credentials issued after 2004 are). What changed in January 2023 is that the CLA credential can no longer be used as the gating credential for MLS Route 3 or MLT Route 2.
MLT Route 2 (the CLA-based MLT bridge) was discontinued on the same date as MLS Route 3. Active MLT routes today are listed on the ASCP MLT credential page — the most relevant for former CLA holders are Route 1 (NAACLS or ABHES MLT program completion) and Route 3 (associate degree or 60 credit hours + 6 chemistry + 6 biology + completion of an accredited MLT program).
ASCP announced the discontinuation in advance of the January 1, 2023 effective date, which gave CLA holders some lead time to either complete a Route 3 application or pivot to an alternative pathway. As of 2026, the route is fully closed — there is no current grandfathering provision for new applications.
Verify directly with the official ASCP source. Any third-party content (textbooks, blog posts, advising documents, study guides, exam prep materials) created before 2023 may still reference Route 3 as if it were active. The authoritative current information is on the ASCP MLS credential page itself, which clearly states the discontinuation.
MLT Route 2 was the equivalent CLA-based pathway for the MLT credential — it allowed CLA holders to sit for the MLT exam. Like MLS Route 3, it was discontinued on January 1, 2023. If you were planning to use MLT Route 2, the active alternatives are MLT Route 1 (program completion) or MLT Route 3 (60 credit hours + 6 chem + 6 bio + accredited program completion).
Yes — provided that at least 5 of those years occurred within the last 10 years. Route 4 specifically requires “5 years of full-time acceptable clinical experience…within the last 10 years.” If you’ve been actively working in a clinical lab through the recent past, you almost certainly meet this requirement. If you retired from lab work more than 10 years ago, you may need to re-engage in clinical practice to qualify.
Yes. ASCP defines acceptable clinical laboratories as those holding CMS CLIA accreditation, DoD CLIP accreditation, JCI accreditation, or accreditation under ISO 15189. The vast majority of US clinical labs operate under CLIA, so this is rarely a problem for domestic experience — but it’s worth verifying with your former lab if there’s any uncertainty.
ASCP publishes detailed content guidelines and reading lists for the MLS exam covering blood banking, chemistry, hematology, immunology, microbiology, molecular biology, and urinalysis/body fluids. Most applicants studying for the MLS exam after Route 4 approval spend 3–6 months in dedicated preparation. The 16+16 prerequisite coursework is foundational to that prep — fresher coursework generally translates to easier exam preparation.
Route 3’s discontinuation isn’t the obstacle it might first appear to be. The route applied to a small and shrinking population — holders of a credential ASCP itself stopped issuing back in 1982. For everyone else, Route 3 was never going to be your path anyway.
If you held a CLA(ASCP) and were planning to bridge to MLS, Route 4 (no prior credential needed) or Route 2 (if you also have MLT) provides a near-identical path. Both require the same 16+16 prerequisite coursework — completable in months, not years, through self-paced online programs from regionally accredited four-year universities.
If you’re a researcher who just hit Route 3 in your reading and were trying to figure out where it fits, the answer is: it doesn’t anymore. The active route framework today is Routes 1, 2, 4, 5, and 6 — and at least one of them applies to you.
| Ready to move forward? If your replacement route requires the 16+16 prerequisite coursework, browse the PrereqCourses.com course catalog or use the free Advisory Service to map your specific transcript against the requirement and identify which courses you need. New sessions begin on the 1st of every month, and Upper Iowa University issues the official transcript directly to ASCP BOC. |
About this guide: Last updated April 2026. Route 3 discontinuation, route requirements, and historical credential information are drawn directly from the ASCP Board of Certification’s official documentation and ASCP BOC History. Always verify current requirements at ascp.org/boc before submitting an application.
