2026 ICD-10-CM Diagnosis Code T36.0X5AAdverse effect of penicillins, initial encounter
T36.0X5A is a billable ICD-10-CM diagnosis code for adverse effect of penicillins, initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 917 through 918. The code is not accepted as a principal diagnosis by the Medicare Code Editor. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Adverse effects of drugs and medicaments, initial encounter.
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for T36.0X5A.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Adverse reaction to amoxicillin and/or clavulanic acid
- Adverse reaction to ampicillin and/or cloxacillin
- Adverse reaction to ampicillin and/or floxacillin
- Adverse reaction to clavulanic acid and/or ticarcillin
- Adverse reaction to piperacillin and/or tazobactam
- Adverse reaction to pivampicillin and/or pivmecillinam
- Allergic reaction caused by antibacterial agent
- Allergic reaction caused by antiinfective agent
- Allergic reaction caused by penicillin
- Amoxycillin adverse reaction
- Ampicillin adverse reaction
- Antipseudomonal penicillins adverse reaction
- Azlocillin adverse reaction
- Bacampicillin adverse reaction
- Benethamine penicillin adverse reaction
- Benzathine penicillin adverse reaction
- Benzylpenicillin adverse reaction
- Broad spectrum penicillins adverse reaction
- Carbenicillin adverse reaction
- Carfecillin adverse reaction
- Ciclacillin adverse reaction
- Cloxacillin adverse reaction
- Drug-induced anaphylaxis
- Drug-induced angioedema-urticaria
- Epstein-Barr virus infectious mononucleosis
- Flucloxacillin adverse reaction
- Infectious mononucleosis ampicillin reaction
- Infectious mononucleosis exanthem
- Maculopapular drug eruption
- Maculopapular eruption
- Mecillinam adverse reaction
- Methicillin adverse reaction
- Mezlocillin adverse reaction
- Penicillin adverse reaction
- Penicillinase-resistant penicillins adverse reaction
- Penicillinase-sensitive penicillins adverse reaction
- Penicillin-induced anaphylaxis
- Penicillin-induced angioedema-urticaria
- Phenethicillin adverse reaction
- Phenoxymethylpenicillin adverse reaction
- Piperacillin adverse reaction
- Pivampicillin adverse reaction
- Pivmecillinam adverse reaction
- Procaine benzylpenicillin adverse reaction
- Talampicillin adverse reaction
- Temocillin adverse reaction
- Ticarcillin adverse reaction
- Urticaria medicamentosa
Coding GuidelinesGuidance
When coding an adverse effect of a drug that has been correctly prescribed and properly administered, assign the appropriate code for the nature of the adverse effect followed by the appropriate code for the adverse effect of the drug.
The appropriate 7th character is to be added to each code from block Poisoning by, adverse effect of and underdosing of systemic antibiotics (T36). Use the following options for the applicable episode of care:
- A - initial encounter
- D - subsequent encounter
- S - sequela
Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2026, published by CMS and the National Center for Health Statistics.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Amoxicillin
a broad-spectrum semisynthetic antibiotic similar to ampicillin except that its resistance to gastric acid permits higher serum levels with oral administration.Amoxicillin-Potassium Clavulanate Combination
a fixed-ratio combination of amoxicillin trihydrate and potassium clavulanate.Ampicillin
semi-synthetic derivative of penicillin that functions as an orally active broad-spectrum antibiotic.Ampicillin Resistance
nonsusceptibility of a microbe to the action of ampicillin, a penicillin derivative that interferes with cell wall synthesis.Pivampicillin
pivalate ester analog of ampicillin.Talampicillin
an ester of ampicillin which is readily hydrolyzed on absorption to release ampicillin. it is well absorbed from the gastrointestinal tract resulting in a greater bioavailability of ampicillin than can be achieved with equivalent doses of ampicillin.Azlocillin
a semisynthetic ampicillin-derived acylureido penicillin.Carbenicillin
broad-spectrum semisynthetic penicillin derivative used parenterally. it is susceptible to gastric juice and penicillinase and may damage platelet function.Carfecillin
the phenyl ester of carbenicillin that, upon oral administration, is broken down in the intestinal mucosa to the active antibacterial. it is used for urinary tract infections.Penicillinase
a beta-lactamase preferentially cleaving penicillins. (dorland, 28th ed) ec 3.5.2.-.Cloxacillin
a semi-synthetic antibiotic that is a chlorinated derivative of oxacillin.Cyclacillin
a cyclohexylamido analog of penicillanic acid.Dicloxacillin
one of the penicillins which is resistant to penicillinase.Cilastatin, Imipenem Drug Combination
combination of imipenem and cilastatin that is used in the treatment of bacterial infections; cilastatin inhibits renal dehydropeptidase i to prolong the half-life and increase the tissue penetration of imipenem, enhancing its efficacy as an anti-bacterial agent.Imipenem
semisynthetic thienamycin that has a wide spectrum of antibacterial activity against gram-negative and gram-positive aerobic and anaerobic bacteria, including many multiresistant strains. it is stable to beta-lactamases. clinical studies have demonstrated high efficacy in the treatment of infections of various body systems. its effectiveness is enhanced when it is administered in combination with cilastatin, a renal dipeptidase inhibitor.Methicillin
one of the penicillins which is resistant to penicillinase but susceptible to a penicillin-binding protein. it is inactivated by gastric acid so administered by injection.Methicillin Resistance
non-susceptibility of a microbe to the action of methicillin, a semi-synthetic penicillin derivative.Methicillin-Resistant Staphylococcus aureus
a strain of staphylococcus aureus that is non-susceptible to the action of methicillin. the mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins.Mezlocillin
semisynthetic ampicillin-derived acylureido penicillin. it has been proposed for infections with certain anaerobes and may be useful in inner ear, bile, and cns infections.Nafcillin
a semi-synthetic antibiotic related to penicillin.Oxacillin
an antibiotic similar to flucloxacillin used in resistant staphylococci infections.Piperacillin
semisynthetic, broad-spectrum, ampicillin derived ureidopenicillin antibiotic proposed for pseudomonas infections. it is also used in combination with other antibiotics.Piperacillin, Tazobactam Drug Combination
an antibiotic combination product of piperacillin and tazobactam, a penicillanic acid derivative with enhanced beta-lactamase inhibitory activity, that is used for the intravenous treatment of intra-abdominal, pelvic, and skin infections and for community-acquired pneumonia of moderate severity. it is also used for the treatment of pseudomonas aeruginosa infections.Sulbactam
a beta-lactamase inhibitor with very weak antibacterial action. the compound prevents antibiotic destruction of beta-lactam antibiotics by inhibiting beta-lactamases, thus extending their spectrum activity. combinations of sulbactam with beta-lactam antibiotics have been used successfully for the therapy of infections caused by organisms resistant to the antibiotic alone.Sulbenicillin
semisynthetic penicillin-type antibiotic.Ticarcillin
an antibiotic derived from penicillin similar to carbenicillin in action.
Table of Drugs and ChemicalsClinical
Substances in the Table of Drugs and Chemicals that reference this code family. Always confirm in the Tabular List before coding.
Patient EducationClinical
Drug Reactions
Most of the time, medicines make our lives better. They reduce aches and pains, fight infections, and control problems such as high blood pressure or diabetes. But medicines can also cause unwanted reactions, such as drug interactions, side effects, and allergies.
The full article covers:
- What is a drug interaction?
- What are side effects?
- What are drug allergies?
- How can I stay safe when taking medicines?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert T36.0X5A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T36.0X5AOverview
Is T36.0X5A (Adverse effect of penicillins) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report adverse effect of penicillins, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T36.0X5A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for adverse effect of penicillins, such as an emergency visit or first evaluation.
What MS-DRG does T36.0X5A group to?
On inpatient claims, adverse effect of penicillins, initial encounter maps to MS-DRG 917, 918, with relative weights from 0.8571 to 1.5684 depending on complications. Higher weights mean higher Medicare reimbursement.
Can T36.0X5A be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because adverse effect of penicillins, initial encounter describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.
What is the ICD-9 equivalent of T36.0X5A?
Under the General Equivalence Mappings, adverse effect of penicillins, initial encounter converts to ICD-9-CM 995.29 (adv eff med/biol NEC/NOS) and E930.0 (adv eff penicillins). The mapping is approximate, so confirm the match fits the documentation.
Footnotes
[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.
