Test Catalog

Test ID: HCQ    
Hydroxychloroquine, Serum

Useful For Suggests clinical disorders or settings where the test may be helpful

Monitoring serum hydroxychloroquine concentrations, assessing compliance, and adjusting dosage in patients

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Hydroxychloroquine is an antimalarial drug used to treat or prevent malaria. It is highly effective against erythrocytic forms of Plasmodium, but not effective against exoerythrocytic forms of parasites. Hydroxychloroquine is also used to treat symptoms of acute or chronic rheumatoid arthritis and systemic lupus erythematosus (SLE).


Adult doses range from 400 mg/week for suppressive therapy to 1200 mg/day for acute malaria attacks. Typical daily doses of 200 to 600 mg are used for SLE and rheumatoid diseases. Hydroxychloroquine has a long terminal elimination half-life in blood (>40 days), which exceed those in plasma. The oral bioavailability averages 75%.


Hydroxychloroquine accumulates in several organs, especially melanin-containing retina and skin. Mild to moderate overdose can result in gastrointestinal effects (ie, nausea, vomiting, and abdominal pain), headache, visual and hearing disturbances, and neuromuscular excitability. Acute hepatitis, cardiotoxicity, and retinopathy may occur with therapeutic doses. The effects of overdosage with hydroxychloroquine include headache, drowsiness, visual disturbances, convulsions, cardiovascular collapse, and respiratory arrest. Toxic retinopathy has also been associated with higher doses and longer duration of use.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

For suppressive treatment of malaria, suggested plasma or serum concentrations should be >10 ng/mL.


For systemic lupus erythematosus, proposed serum target concentrations should be > or =500 ng/mL.

Interpretation Provides information to assist in interpretation of the test results

The serum concentration should be interpreted in the context of the patient's clinical response and may provide useful information in patients showing poor response, noncompliance, or adverse effects. Concentrations less than 106 ng/mL have been associated with non-compliance.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Specimens that are obtained from serum gel tubes are not acceptable, as the drug can absorb on the gel and lead to falsely decreased concentrations.


Hydroxychloroquine is currently under investigational use for the prevention or post-exposure prophylaxis and treatment of coronavirus disease 2019 (COVID-19); the safety and efficacy of its use has not been established.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. McChesney EW BW, McAuliff JP: Laboratory studies on the 4-aminoquinoline antimalarials: II. Plasma levels of chloroquine and hydroxychloroquine in man after various oral dosage regimens. Antibiot Chemother (Northfield) 1962;12:583-594

2. Mok CC, Penn HJ, Chan KL, Tse SM, Langman LJ, Jannetto PJ. Hydroxychloroquine serum concentrations and flares of systemic lupus erythematosus: A longitudinal cohort analysis. Arthritis Care Res. 2016 Sep;68(9):1295-1302. doi: 10.1002/acr.22837

3. Durcan L, Clarke WA, Magder LS, Petri M. Hydroxychloroquine blood levels in systemic lupus erythematosus: clarifying dosing controversies and improving adherence. J Rheumatol. 2015 Nov;42(11):2092-2097. doi: 10.3899/jrheum.150379

4. Blanchet B, Jallouli M, Allard M, et al. SATO188 Whole blood versus serum hydroxychloroquine levels for drug monitoring of patients with systemic lupus erythematosus: preliminary results of a pharmacological study. Ann Rheum Dis. 2019;78(2):1168-1169

5.Soichot M, Megarbane B, Houze P, et al: Development, validation and clinical application of a LC-MS/MS method for the simultaneous quantification of hydroxychloroquine and its active metabolites in human whole blood. J Pharm Biomed Anal. 2014 Nov;100:131-137. doi: 10.1016/j.jpba.2014.07.009

6. Wang LZ, Ong RY, Chin TM, et al: Method development and validation for rapid quantification of hydroxychloroquine in human blood using liquid chromatography-tandem mass spectrometry.J Pharm Biomed Anal. 2012 Mar 5;61:86-92. doi: 10.1016/j.jpba.2011.11.034

7. Disposition of Toxic Drugs and Chemicals in Man. 10th ed. Biomedical Publications; 2014

8. Tett SE, Cutler DJ, Day RO, Brown KF: A dose-ranging study of the pharmacokinetics of hydroxy-chloroquine following intravenous administration to healthy volunteers. Brit J Clin Pharmaco. 1988;26(3):303-313

9. Gautret P, Lagier J-C, Parola P, et al: Hydroxychloroquine and azithromycin as a treatment of COVID-19: results of an open-label non-randomized clinical trial. Int J Antimicrob Agents. 2020 Mar 20:105949. doi: 10.1016/j.ijantimicag.2020.105949

10. Kim S-H: Comparison of lopinavir/ritonavir or hydroxychloroquine in patients with mild coronavirus disease (COVID-19). US National Library of Medicine (NLM). 2020. Accessed 03/2020. Available at clinicaltrials.gov/ct2/show/NCT04307693

11. Lu H: Efficacy and safety of hydroxychloroquine for treatment of pneumonia caused by 2019-nCoV (HC-nCoV). US National Library of Medicine (NLM). 2020. Accessed 03/2020. Available at clinicaltrials.gov/ct2/show/NCT04261517

12. Post-exposure prophylaxis for SARS-coronavirus-2. US National Library of Medicine (NLM). 2020. Accessed 03/2020. Available at clinicaltrials.gov/ct2/show/NCT04308668