Glutamine (Endari) Shortage: What Providers and Prescribers Need to Know in 2026

For hematologists, oncologists, pediatricians, and primary care providers managing patients with sickle cell disease (SCD), L-glutamine (Endari) represents both an important therapeutic option and a significant access challenge. While there is no active FDA shortage of Glutamine as of 2026, a complex web of insurance requirements, specialty pharmacy restrictions, and high costs means many patients never successfully fill their prescriptions.

This guide provides an up-to-date overview of the Glutamine access landscape for prescribers — including what's changed in 2024–2026, what insurance payers require, and how to navigate the process efficiently for your patients.

Clinical Context: Where Glutamine Fits in SCD Treatment

Glutamine (L-glutamine oral powder, brand Endari) was approved by the FDA in July 2017 for the reduction of acute complications of sickle cell disease in adults and pediatric patients 5 years of age and older. It was the first new SCD treatment in nearly 20 years and remains one of six FDA-approved pharmacotherapies for SCD alongside hydroxyurea, crizanlizumab, and two gene therapies (Casgevy and Lyfgenia).

Glutamine's mechanism involves increasing the NAD redox potential in sickle red blood cells by improving glutathione availability, thereby reducing oxidative damage and the frequency of vaso-occlusive crises (VOCs). The Phase 3 trial demonstrated a statistically significant reduction in pain crises (median 3 vs. 4 with placebo, p=0.005) and a 33% reduction in hospitalizations over 48 weeks.

Importantly, 63.4% of trial patients were on concurrent hydroxyurea, confirming that Glutamine can be safely used alongside the mainstay of SCD pharmacotherapy.

The Access Gap: What Real-World Data Shows

A 10-month observational study at Montefiore Medical Center following 101 patients prescribed L-glutamine found that:

Only 21% were actively taking the medication at follow-up

43% had discontinued treatment

33% never filled the prescription

Insurance-related barriers were among the top contributing factors. This study highlights that prescribing Glutamine is only the first step — helping patients successfully obtain it requires proactive pharmacy and payer navigation.

Insurance Coverage Requirements (2025–2026)

Glutamine (Endari) is classified as a specialty medication and placed on Tier 5 of most Medicare Part D formularies — the highest-cost tier. Commercial formularies vary but generally require prior authorization.

UnitedHealthcare Commercial (effective 5/1/2025): Requires diagnosis of SCD AND either (a) concurrent hydroxyurea therapy, or (b) documented contraindication or intolerance to hydroxyurea.

Molina Healthcare: Requires PA; notes limited evidence for pharmaceutical-grade glutamine over OTC supplements and no head-to-head comparisons with hydroxyurea.

Medicare Part D: Tier 5 placement; requires prior authorization and quantity limits at most plans. With the Part D $2,000 OOP cap effective 2025, cost burden may be lower for Medicare patients who reach the cap.

Prior Authorization Best Practices for Prescribers

When submitting a prior authorization for Glutamine, include:

Confirmed diagnosis of sickle cell disease (ICD-10: D57.0, D57.1, D57.2, D57.4, D57.8)

Documentation of current or prior hydroxyurea use, or clinical rationale for inability to use hydroxyurea

History of VOCs: frequency, severity, hospitalizations in past 12 months

Intended dose (weight-based: 0.3 g/kg twice daily, max 30 g/day)

Reference the Phase 3 published trial (Niihara et al., NEJM 2018) for clinical justification

2024 Update: Generic Availability and Impact of Voxelotor Withdrawal

Two significant events in 2024 affected the SCD treatment landscape:

July 2024: ANI Pharmaceuticals launched the first FDA-approved AA-rated generic L-glutamine oral powder. U.S. annual sales are approximately $20 million. Generic availability may improve long-term pricing and insurance formulary positioning, though specialty pharmacy requirements remain.

September 2024: Pfizer voluntarily withdrew voxelotor (Oxbryta) due to safety concerns (higher VOC-related death rate in post-approval trial). Providers should transition affected patients to remaining approved options. Glutamine and crizanlizumab remain available; hydroxyurea continues as first-line standard of care.

Patient Assistance Resources to Share With Your Patients

Endari Copay Assistance Program: Commercially insured patients pay as little as $10/month. Call 855-723-5646 or visit endarirx.com/copay-assistance.

Endari Support Program: For uninsured/underinsured patients — minimal or no-cost medication. Call 1-855-723-5646.

GoodRx coupons: Can reduce cash price from ~$3,200 to ~$1,013 per 30-day supply at participating specialty pharmacies.

medfinder: A service that calls pharmacies near patients to check which ones have Glutamine in stock — reducing the frustration of pharmacy searches for patients and their caregivers.

When to Consider Alternatives to Glutamine

If insurance denials are sustained after appeal, or if the patient cannot access or afford Glutamine despite assistance programs, consider:

Hydroxyurea optimization: Many patients are underdosed on hydroxyurea. Optimizing to maximum tolerated dose may reduce VOC burden.

Crizanlizumab (Adakveo): Monthly IV infusion for ages 16+. Different mechanism (P-selectin inhibition) with strong evidence for VOC reduction.

Gene therapy referral: For appropriate candidates, refer to a center offering Casgevy (exa-cel) or Lyfgenia (lov-cel) evaluation.

Help your patients access their medications more easily. Learn about medfinder for providers or read our provider's guide to helping patients find Glutamine in stock.