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Gwendolyn A. McMillin

Gwendolyn A. McMillin, PhD

Languages spoken: English

Academic Information

Departments Primary - Pathology

Board Certification

  • American Board of Clinical Chemistry (Sub: Clinical Chemistry)
  • American Board of Clinical Chemistry (Sub: Toxicological Chemistry)

Dr. McMillin is a Medical Director of the Toxicology and Trace Elements laboratories and Co-Medical Director of Pharmacogenetics at ARUP, as well as a Professor of Pathology at the University of Utah School of Medicine. Dr. McMillin is certified by the American Board of Clinical Chemistry in clinical chemistry and toxicological chemistry.

Education History

Postdoctoral Fellowship University of Utah School of Medicine
Postdoctoral Fellow
University of Utah
Undergraduate Grinnell College

Selected Publications

Journal Article

  1. Baryeh K, Zhou R, Brown E, McMillin GA, Krasowski MD, Johnson-Davis KL (2024). Retrospective Data Analysis Reveals Unusual Metabolism Pattern of Ethanol in Pediatrics as Compared to Adult and Geriatric Populations. J Appl Lab Med. (Read full article)
  2. McMillin GA, Morad AW, Boyd JM, Johnson-Davis KL, Metz TD, Smid MC, Krasowski MD (2024). Biological Testing and Interpretation of Laboratory Results Associated with Detecting Newborns with Substance Exposure. Clin Chem. (Read full article)
  3. Boyd JM, Kelly BN, McMillin GA (2024). Prevalence of Gabapentinoid and Opioid Copositives in a Reference Laboratory Patient Population. J Appl Lab Med. (Read full article)
  4. Watson CJ, McMillin GA, Burns MM (2024). False-Negative Confirmatory Testing in Patients With Cannabinoid-Positive Urine Drug Screens. JAMA Pediatr, 178(2), 199-201. (Read full article)
  5. Hughs ML, McMillin GA (2023). 11-Nor-9-Carboxy-Δ8-Tetrahydrocannabinol, 7-Carboxy Cannabidiol, and 11-Nor-9-Carboxy-Δ9-Tetrahydrocannabinol in Urine by LC-MS/MS. Methods Mol Biol, 2737, 161-174. (Read full article)
  6. Merrigan SD, Yang YK, McMillin GA, Boyd JM (2023). Detection of 41 Drugs and Metabolites in Urine with Internal Hydrolysis Control by Liquid Chromatography-Tandem Mass Spectrometry. Methods Mol Biol, 2737, 229-247. (Read full article)
  7. Metz TD, Allshouse AA, McMillin GA, Greene T, Chung JH, Grobman WA, Haas DM, Mercer BM, Parry S, Reddy UM, Saade GR, Simhan HN, Silver RM (2023). Cannabis Exposure and Adverse Pregnancy Outcomes Related to Placental Function. JAMA, 330(22), 2191-2199. (Read full article)
  8. Snozek CLH, McMillin GA, Nwosu A, Dizon A, Krasowski MD (2022). Nicotine and Tobacco Alkaloid Testing and Challenges: Lessons Learned From a College of American Pathologists Proficiency Testing Survey. Arch Pathol Lab Med, 147(6), 634-642. (Read full article)
  9. Bithi N, Merrigan SD, McMillin GA (2022). Does Labetalol Trigger False Positive Drug Testing Results? J Addict Med, 17(3), e209-e210. (Read full article)
  10. Pandya V, McMillin GA, Young BA (2022). Deceptively Simple: Can Urine Samples from CLIA-Waived Urine Drug Screen Devices Be Reused for Confirmatory Testing? J Appl Lab Med, 8(2), 341-346. (Read full article)
  11. Pandya V, Wilker C, McMillin GA (2021). Can Umbilical Cord and Meconium Results Be Directly Compared? Analytical Approach Matters. J Anal Toxicol, 47(1), 96-105. (Read full article)
  12. Hughs M, Kish-Trier E, OBrien A, McMillin GA (2022). Analysis of Mitragynine and Speciociliatine in Umbilical Cord by LC-MS-MS for Detecting Prenatal Exposure to Kratom. J Anal Toxicol, 46(9), 957-964. (Read full article)
  13. Marzinke MA, Clarke W, Dietzen DJ, Hoofnagle AN, McMillin GA, Willrich MAV (2022). The VALIDity of Laboratory Developed Tests: Leave it to the experts? J Mass Spectrom Adv Clin Lab, 27, 1-6. (Read full article)
  14. Smid MC, Allshouse AA, McMillin GA, Nunez K, Cavin T, Worden J, Buchi K, Muniyappa B, Varner MW, Cochran G, Metz TD (2022). Umbilical Cord Collection and Drug Testing to Estimate Prenatal Substance Exposure in Utah. Obstet Gynecol, 140(2), 153-162. (Read full article)
  15. Bajaj AO, Kushnir MM, Kish-Trier E, Law RN, Zuromski LM, Molinelli AR, McMillin GA, Johnson-Davis KL (2022). LC-MS/MS Method for Measurement of Thiopurine Nucleotides (TN) in Erythrocytes and Association of TN Concentrations With TPMT Enzyme Activity. Front Pharmacol, 13, 836812. (Read full article)
  16. Hunsaker JJH, Laulu SL, LaGrave D, Murphy W, Reichman HA, Snow TM, McMillin GA, Johnson-Davis KL, Genzen JR (2021). Tobacco and Cannabis Use During Pregnancy. Am J Clin Pathol, 157(1), 146-152. (Read full article)
  17. Langman LJ, Gaskins J, Korte E, Maluf C, Wooderchak-Donahue WL, McMillin GA, Jannetto PJ, Hartley B, Malkani A, Yakkanti M, Jortani SA (2021). Endogenous and iatrogenic sources of variability in response to opioid therapy in Post-Surgical and injured orthopedic patients. Clin Chim Acta, 522, 105-113. (Read full article)
  18. Nelson HA, Wood KE, McMillin GA, Krasowski MD (2021). Umbilical Cord Drug Screening in Multiple Births: Experience from a Reference Laboratory and Academic Medical Center. J Anal Toxicol, 46, 611-618. (Read full article)
  19. Metz TD, McMillin GA, Silver RM, Allshouse AA, Heard K, Jensen TL, Wymore EM, Stickrath E, Conageski C, Kinney GL, Binswanger IA (2022). Quantification of Prenatal Marijuana Use: Evaluation of the Correlation between Self-Report, Serum, Urine and Umbilical Cord Assays among Women Delivering at Two Urban Colorado Hospitals. Addiction, 117(1), 172-181. (Read full article)
  20. Khushman M, Patel GK, Maharjan AS, McMillin GA, Nelson C, Hosein P, Singh AP (2021). The prevalence and clinical relevance of 2R/2R TYMS genotype in patients with gastrointestinal malignancies treated with fluoropyrimidine-based chemotherapy regimens. Pharmacogenomics J, 21(3), 308-317. (Read full article)
  21. Okoye NC, McMillin GA (2020). Patterns of Neonatal Co-Exposure to Gabapentin and Commonly Abused Drugs Observed in Umbilical Cord Tissue. J Anal Toxicol, 45(5), 506-512. (Read full article)
  22. Bernard PS, Wooderchak-Donahue W, Wei M, Bray SM, Wood KC, Parikh B, McMillin GA (2021). Potential Utility of Pre-Emptive Germline Pharmacogenetics in Breast Cancer. Cancers (Basel), 13(6). (Read full article)
  23. McMillin GA, Johnson-Davis KL, Kelly BN, Scott B, Yang YK (2020). Impact of the Opioid Epidemic on Drug Testing. Ther Drug Monit, 43(1), 14-24. (Read full article)
  24. Moyer AM, McMillin GA, Long TA, Gandhi MJ, Mao R, Smock KJ, Halley JG, Weck KE (2020). Genotype and Phenotype Concordance for Pharmacogenetic Tests Through Proficiency Survey Testing. Arch Pathol Lab Med, 144(9), 1057-1066. (Read full article)
  25. Yang YK, Johnson-Davis KL, Kelly BN, McMillin GA (2020). Demand for Interpretation of a Urine Drug Testing Panel Reflects the Changing Landscape of Clinical Needs; Opportunities for the Laboratory to Provide Added Clinical Value. J Appl Lab Med, 5(5), 858-868. (Read full article)
  26. Smy L, Sadler AJ, McMillin GA (2020). Evaluation of Imatinib Concentrations in Samples Submitted for BCR-ABL1 or Imatinib Testing-Evidence to Support Therapeutic Drug Monitoring for Dose Optimization? Ther Drug Monit, 42(4), 559-564. (Read full article)
  27. Kroner GM, Johnson-Davis KL, Doyle K, McMillin GA (2019). Cannabinol (CBN) Cross-Reacts with Two Urine Immunoassays Designed to Detect Tetrahydrocannabinol (THC) Metabolite. J Appl Lab Med, 5(3), 569-574. (Read full article)
  28. Krasowski MD, McMillin GA, Melanson SEF, Dizon A, Magnani B, Snozek CLH (2019). Interpretation and Utility of Drug of Abuse Screening Immunoassays: Insights From Laboratory Drug Testing Proficiency Surveys. Arch Pathol Lab Med, 144(2), 177-184. (Read full article)
  29. Kim K, McMillin GA, Bernard PS, Tantravahi S, Walker BS, Schmidt RL (2019). Cost effectiveness of therapeutic drug monitoring for imatinib administration in chronic myeloid leukemia. PLoS One, 14(12), e0226552. (Read full article)
  30. Gaedigk A, Turner A, Everts RE, Scott SA, Aggarwal P, Broeckel U, McMillin GA, Melis R, Boone EC, Pratt VM, Kalman LV (2019). Characterization of Reference Materials for Genetic Testing of CYP2D6 Alleles: A GeT-RM Collaborative Project. J Mol Diagn, 21(6), 1034-1052. (Read full article)
  31. Gage BF, Bass AR, Lin H, Woller SC, Stevens SM, Al-Hammadi N, Anderson JL, Li J, Rodriguez T Jr, Miller JP, McMillin GA, Pendleton RC, Jaffer AK, King CR, Whipple B, Porche-Sorbet R, Napoli L, Merritt K, Thompson AM, Hyun G, Hollomon W, Barrack RL, Nunley RM, Moskowitz G, Dvila-Romn V, Eby CS (2019). Effect of Low-Intensity vs Standard-Intensity Warfarin Prophylaxis on Venous Thromboembolism or Death Among Patients Undergoing Hip or Knee Arthroplasty: A Randomized Clinical Trial. JAMA, 322(9), 834-842. (Read full article)
  32. Maharjan AS, McMillin GA, Patel GK, Awan S, Taylor WR, Pai S, Frankel AE, Nelson C, Wang B, Hosein PJ, Singh AP, Khushman M (2019). The Prevalence of DPYD*9A(c.85T>C) Genotype and the Genotype-Phenotype Correlation in Patients with Gastrointestinal Malignancies Treated With Fluoropyrimidines: Updated Analysis. Clin Colorectal Cancer, 18(3), e280-e286. (Read full article)
  33. Wood KE, McMillin GA, Krasowski MD (2019). Risk-Based Newborn Drug Testing in a Setting With a Low Prevalence of Maternal Drug Use. Hosp Pediatr, 9(8), 593-600. (Read full article)
  34. Melis R, Mohamed J, Ha Y, Lyon E, McMillin G (2018). Postmortem CYP2D6 Genotyping and Copy Number Determinations Using DNA Extracted from Archived FTA Bloodstains. J Anal Toxicol, 43(5), 411-414. (Read full article)
  35. Wu F, Melis R, McMillin GA, Johnson-Davis KL (2018). Retrospective Data Analysis of the Influence of Age and Sex on TPMT Activity and Its Phenotype-Genotype Correlation. J Appl Lab Med, 3(5), 827-838. (Read full article)
  36. Jensen TL, Wu F, McMillin GA (2019). Detection of in utero Exposure to Cannabis in Paired Umbilical Cord Tissue and Meconium by Liquid Chromatography-Tandem Mass Spectrometry. Clin Mass Spectrom, 14 Pt B, 115-123. (Read full article)
  37. McMillin GA (2017). Pharmacogenetics of Opioid Use and Implications for Pain Management-Are We Ready? J Appl Lab Med, 2(4), 481-484. (Read full article)
  38. Jannetto PJ, Bratanow NC, Clark WA, Hamill-Ruth RJ, Hammett-Stabler CA, Huestis MA, Kassed CA, McMillin GA, Melanson SE, Langman LJ (2017). Executive Summary: American Association of Clinical Chemistry Laboratory Medicine Practice Guideline-Using Clinical Laboratory Tests to Monitor Drug Therapy in Pain Management Patients. J Appl Lab Med, 2(4), 489-526. (Read full article)
  39. McMillin GA (2017). Drug Detection in Urine for Evaluating Exposure-No Limits! J Appl Lab Med, 2(4), 648-652. (Read full article)
  40. Leung EKY, Agolini E, Pei X, Melis R, McMillin GA, Friedman PN, Peterson P, Danahey K, ODonnell PH, Yeo KJ (2016). Validation of an Extensive CYP2D6 Assay Panel Based on Invader and TaqMan Copy Number Assays. J Appl Lab Med, 1(5), 471-482. (Read full article)
  41. Do EJ, Lenzini P, Eby CS, Bass AR, McMillin GA, Stevens SM, Woller SC, Pendleton RC, Anderson JL, Proctor P, Nunley RM, Davila-Roman V, Gage BF (2011). Genetics informatics trial (GIFT) of warfarin to prevent deep vein thrombosis (DVT): rationale and study design. Pharmacogenomics J, 12(5), 417-24. (Read full article)
  42. Lee CC, McMillin GA, Babic N, Melis R, Yeo KT (2011). Evaluation of a CYP2C19 genotype panel on the GenMark eSensor® platform and the comparison to the Autogenomics Infiniti™ and Luminex CYP2C19 panels. Clin Chim Acta, 412(11-12), 1133-7. (Read full article)
  43. Juenke JM, Brown PI, Johnson-Davis KL, McMillin GA (2011). Simultaneous quantification of levetiracetam and gabapentin in plasma by ultra-pressure liquid chromatography coupled with tandem mass spectrometry detection. Ther Drug Monit, 33(2), 209-13. (Read full article)
  44. McMillin GA, Juenke JM, Johnson MJ, Dasgupta A (2011). Discordant carbamazepine values between two immunoassays: carbamazepine values determined by ADVIA Centaur correlate better with those determined by LC-MS/MS than PETINIA assay. J Clin Lab Anal, 25(3), 212-6. (Read full article)
  45. Marin SJ, McMillin GA (2010). LC-MS/MS analysis of 13 benzodiazepines and metabolites in urine, serum, plasma, and meconium. Methods Mol Biol, 603, 89-105. (Read full article)
  46. Marin SJ, Keith L, Merrell M, McMillin GA (2009). Comparison of drugs of abuse detection in meconium by EMIT II and ELISA. J Anal Toxicol, 33(3), 148-54. (Read full article)
  47. Melis R, Lyon E, McMillin GA (2006). Determination of CYP2D6, CYP2C9 and CYP2C19 genotypes with Tag-It mutation detection assays. Expert Rev Mol Diagn, 6(6), 811-20. (Read full article)
  48. Juenke JM, Brown PI, Urry FM, McMillin GA (2006). Drug monitoring and toxicology: a procedure for the monitoring of oxcarbazepine metabolite by HPLC-UV. J Chromatogr Sci, 44(1), 45-8. (Read full article)


  1. Metz TD, Allshouse AA, McMillin GA, Silver RM, Smid MC, Haas DM, Simhan HN, Saade GR, Grobman WA, Parry S, Chung JH, Jarlenski MP (2022). Association of Cannabis Use With Nausea and Vomiting of Pregnancy. [Letter to the editor]. Obstet Gynecol, 140(2), 266-270. (Read full article)