Your genes make enzymes that affect how your body processes (metabolizes) certain medicines. An enzyme is a protein that speeds up chemical reactions in your body.
It’s common to have changes in genes that cause your body to process medicines differently than other people. Because of these changes in your genes, you could be very sensitive to some medicines, some medicines may not work for you as well as expected, or some medicines may work for you as expected.
Medicines can also interact with how an enzyme works, which is why it is important to tell your healthcare providers when you’re taking more than one medicine at the same time.
Your healthcare providers can use your test results to help decide what medicines will work well for you and what doses to prescribe.
Be sure to share your test results with all your healthcare providers. Your genes stay the same as you get older, so your results won’t change. Your results can affect how medicines are prescribed for you throughout your life.
Remember: Never make any changes to your medicines without talking to your healthcare provider first.
Understanding your test results
CYP2B6 gene
Cytochrome P450 2B6 (CYP2B6) is the gene that makes an enzyme that processes:
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antidepressant medicine —sertraline
-
HIV medicine —efavirenz
Your CYP2B6 test results will put you in a metabolizer group:
- Poor: The CYP2B6 enzyme has no activity. This means your body processes some medicines very slowly, and you may need lower doses or different medicines. About 8% of people are CYP2B6 poor metabolizers.
- Intermediate: The CYP2B6 enzyme has low activity. This means your body processes some medicines slower than expected, and you may need lower doses. About 38% of people are CYP2B6 intermediate metabolizers.
- Normal: The CYP2B6 enzyme has normal activity. This means your body processes some medicines at a typical rate, and you can use a standard dose of these medicines. About 38% of people are CYP2B6 normal metabolizers.
- Rapid: The CYP2B6 enzyme has high activity. This means your body processes some medicines quickly, and you may need different doses or a different medicine. About 5% of people are CYP2B6 rapid metabolizers.
- Ultrarapid: The CYP2B6 enzyme has very high activity. This means your body processes some medicines very quickly, and you likely need to take a different dose or a different medicine. Less than 1% of people are CYP2B6 ultrarapid metabolizers.
CYP2C gene cluster
CYP2C gene cluster (similar genes that work together) is a grouping of genes that affect how your body responds to the blood thinner
warfarin.
Research so far shows that the CYP2C gene cluster has an effect mainly in adults of West African ancestry.
Your test results for the CYP2C gene cluster will put you in a cluster function group:
- Normal: Your body responds to warfarin as expected, and you can likely start taking it at a standard dose.
- Sensitive: Your body is sensitive to warfarin, and you may need to start taking it at a lower dose.
- Most sensitive: Your body is very sensitive to warfarin, and you may need to start taking it at a lower dose.
Your healthcare provider will also look at your other gene test results and factors like your diet before they decide what dose of warfarin to prescribe.
CYP2C9
Cytochrome P450 2C9 (CYP2C9) is the gene that makes an enzyme that helps your body process:
-
non-steroidal anti-inflammatory drugs (NSAIDs) for pain—ibuprofen, celecoxib, flurbiprofen, lornoxicam, meloxicam, tenoxicam, piroxicam
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seizure medicines—phenytoin and fosphenytoin
-
other medicines—the blood thinner warfarin, fluvastatin for high cholesterol, and siponimod to treat multiple sclerosis
Your CYP2C9 test results will put you in a metabolizer group:
- Poor: The CYP2C9 enzyme has no activity. This means your body processes medicines very slowly, and you may need lower doses or different medicines. About 2% of people are poor metabolizers.
- Intermediate: The CYP2C9 enzyme has low activity. This means your body processes medicines more slowly than expected, and you may need lower doses. About 29% of people are intermediate metabolizers.
- Normal: The CYP2C9 enzyme has normal activity. This means your body processes medicines at a typical rate, and you can use a standard dose of these medicines. About 64% of people are normal metabolizers.
CYP2C19 gene
Cytochrome P450 2C19 (CYP2C19) is the gene that makes an enzyme that processes:
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antidepressant medicines—sertraline, escitalopram, citalopram, amitriptyline, clomipramine, doxepin, imipramine, trimipramine
-
proton pump inhibitors—omeprazole, lansoprazole, pantoprazole, and dexlansoprazole (all used for acid reflux or heartburn)
-
other medicines—clopidogrel (for clotting) and voriconazole (for fungal infections)
Your CYP2C19 test results will put you in a metabolizer group:
- Poor: The CYP2C19 enzyme has no activity. This means your body processes some medicines very slowly, and you may need lower doses or different medicines. About 3% of people are poor metabolizers.
- Intermediate: The CYP2C19 enzyme has low activity. This means your body processes some medicines more slowly than expected, and you may need lower doses. About 21% of people are intermediate metabolizers.
- Normal: The CYP2C19 enzyme has normal activity. This means your body processes some medicines at a typical rate, and you can use a standard dose of these medicines. About 43% of people are normal metabolizers.
- Rapid: The CYP2C19 enzyme has high activity. This means your body processes some medicines more quickly, and you may need higher doses or a different medicine. About 29% of people are rapid metabolizers.
- Ultrarapid: The CYP2C19 enzyme has very high activity. This means your body processes some medicines very quickly, and you likely need higher doses or a different medicine. About 5% of people are ultrarapid metabolizers.
CYP2D6
Cytochrome P450 2D6 (CYP2D6) is the gene that makes an enzyme that processes:
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ADHD medicines—amphetamine, atomoxetine
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antidepressants medicines—amitriptyline, clomipramine, desipramine, doxepin, fluoxetine, fluvoxamine, imipramine, nortriptyline, paroxetine, trimipramine, venlafaxine, vortioxetine
-
antipsychotic medicines—aripiprazole, haloperidol, perphenazine, pimozide, risperidone, thioridazine, zuclopenthixol
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pain medicines—codeine, hydrocodone, oxycodone, and tramadol
-
other medicines—ondansetron and metoclopramide for nausea and vomiting, metoprolol for high blood pressure, eliglustat for Gaucher disease
Your CYP2D6 test results will put you in a metabolizer group:
- Poor: The CYP2D6 enzyme has no activity. This means your body processes some medicines very slowly, and you may need lower doses or different medicines. About 6% of people are CYP2D6 poor metabolizers.
- Intermediate: The CYP2D6 enzyme has low activity. This means your body processes some medicines more slowly, and you may need lower doses. About 7% of people are CYP2D6 intermediate metabolizers.
- Normal: The CYP2D6 enzyme has normal activity. This means your body processes some medicines at an expected rate, and you can use a standard dose of these medicines. About 85% of people are CYP2D6 normal metabolizers.
- Ultrarapid: The CYP2D6 enzyme has very high activity. This means your body processes some medicines very quickly, and you likely need higher doses or a different medicine. About 5% of people are CYP2D6 ultrarapid metabolizers.
CYP3A4
Cytochrome P450 3A4 (CYP3A4) is the gene that makes an enzyme that processes:
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antipsychotic medicine—quetiapine
-
immunosuppressant—tacrolimus (to prevent organ rejection after transplant)
Your CYP3A4 test results will put you in a metabolizer group:
- Poor: The CYP3A4 enzyme has no activity. This means your body processes some medicines very slowly, and you may need lower doses or different medicines.
- Intermediate: The CYP3A4 enzyme has decreased activity. This means your body processes some medicines more slowly, and you may need lower doses.
- Normal: The CYP3A4 enzyme has normal activity. This means your body processes some medicines at an expected rate, and you can use a standard dose of these medicines.
DPYD
Dihydropyrimidine dehydrogenase (DPYD) is the gene that makes an enzyme that processes the cancer medicines
5-fluorouracil and
capecitabine.
Your DPYD test results will put you in a metabolizer group:
- Poor: The DPYD enzyme has no activity. This means your body processes some medicines very slowly, and you may need lower doses or different medicines.
- Intermediate: The DPYD enzyme has low activity. This means your body processes some medicines more slowly, and you may need lower doses.
- Normal: The DPYD enzyme has normal activity. This means your body processes some medicines at an expected rate, and you can use a standard dose of these medicines.
CYP4F2
Cytochrome P450 4F2 (CYP4F2) is the gene that makes an enzyme that regulates vitamin K, which helps your blood clot. It affects how your body processes the blood thinner
warfarin.
Your DPYD test results will put you in a metabolizer group:
- Poor: The CYP4F2 enzyme has very low activity. This means you may need a higher starting dose of warfarin.
- Intermediate: The CYP4F2 enzyme has lower activity. This means you may need a higher starting dose of warfarin.
- Normal: The CYP4F2 enzyme has normal activity. This means your body responds to warfarin as expected.
Your healthcare provider will look at your other gene test results and factors like your diet before they decide what dose of warfarin to prescribe.
CYP3A5
Cytochrome P450 3A5 (CYP3A5) is the gene that makes an enzyme that processes the immunosuppressant
tacrolimus, which is used to prevent organ transplant rejection.
Your CYP3A5 test results will put you in a metabolizer group:
- Poor: The CYP3A5 enzyme has low activity. This means your body processes some medicines more slowly. But because most people (about 68%) are CYP3A5 poor metabolizers, a standard dose is often right for you.
- Intermediate: The CYP3A5 enzyme has increased activity compared to most people, who are in the poor metabolizer group. Your body processes some medicines more quickly, and you may need higher doses. About 22% of people are CYP3A5 intermediate metabolizers.
- Normal: The CYP3A5 enzyme has high activity compared to most people who are in the poor metabolizer group. Your body processes some medicines quickly, and you may need higher doses. About 4% of people are CYP3A5 normal metabolizers.
HLA-A and HLA-B
HLA-A and HLA-B are genes that help your immune system recognize and fight infections. Some people inherit changes in these genes that can increase the risk of serious skin reactions to certain medicines. Different HLA gene changes affect different medicines:
- HLA-A*31:01—carbamazepine
- HLA-B*15:02—carbamazepine, oxcarbazepine, phenytoin, fosphenytoin, and lamotrigine
- HLA-B*57:01—abacavir
- HLA-B*58:01—allopurinol
If you have one of these genetic changes, taking the related medicine can put you at a higher risk of having a serious skin reaction. These skin reactions are rare, but they can be life-threatening. Your healthcare provider may recommend a different medicine if you have one of the changes.
Your test results will be reported as either negative or positive for each HLA gene that was tested:
- Negative: You do
not have one of the tested HLA gene changes. Your risk of a serious skin reaction to the related medicine is lower, but no medicine is completely risk free.
- Positive: You
do have one of the tested HLA gene changes. Your risk of a serious skin reaction to the related medicine is higher. Your healthcare provider may recommend a different medicine to help reduce your risk.
NUDT15
Nudix hydrolase 15 (NUDT15) is the gene that makes an enzyme that processes medicines used to treat cancer and autoimmune diseases (thiopurines)—azathioprine, mercaptopurine, and
thioguanine.
Your NUDT15 test results will put you in a metabolizer group:
- Poor: The NUDT15 enzyme has little to no activity. This means your body processes some medicines slowly, and you may need lower doses or different medicines. Less than 1% of people are poor metabolizers.
- Intermediate: The NUDT15 enzyme has low activity. This means your body processes some medicines a bit slower than expected, and you may need lower doses. About 2% of people are intermediate metabolizers.
- Normal: The NUDT15 enzyme has normal activity. This means your body processes some medicines as expected, and you can use a standard dose of these medicines. About 74% of people are normal metabolizers.
SLCO1B1
Solute carrier organic anion transporter family member 1B1 (SLCO1B1) is the gene that makes a transporter to help move medicines into your cells where they can work properly.
SLCO1B1 affects how your body processes cholesterol medicines called
statins—atorvastatin, fluvastatin, lovastatin, pravastatin, simvastatin, and rosuvastatin.
Your SLCO1B1 test results will put you in a function group:
- Poor: The transporter has no activity. This means your body processes some medicines much slower than is usual, and you may need lower doses. About 3% of people have poor function for SLCO1B1.
- Decreased: The transporter has low activity. This means your body processes some medicines slowly, and you may need lower doses. About 28% of people have decreased function for SLCO1B1.
- Normal: The transporter has normal activity. This means your body processes medicines as expected, and you can take a standard dose of these medicines. About 66% of people have normal function for SLCO1B1.
- Increased: The transporter has higher activity. This means your body processes some medicines faster than is usual, and you often need higher doses. About 3% of people have increased function for SLCO1B1.
TPMT
Thiopurine methyltransferase (TPMT) is the gene that makes an enzyme that processes medicines used to treat cancer and autoimmune diseases (thiopurines)—azathioprine, mercaptopurine, and
thioguanine.
Your TPMT test results will put you in a metabolizer group:
- Poor: The TPMT enzyme has no activity. This means your body processes some medicines very slowly, and you may need lower doses or different medicines. Less than 1% of people are TPMT poor metabolizers.
- Intermediate: The TPMT enzyme has low activity. This means your body processes some medicines more slowly, and you may need lower doses. About 8% of people are TPMT intermediate metabolizers.
- Normal: The TPMT enzyme has normal activity. This means your body processes some medicines as expected, and you can use a standard dose of these medicines. About 85% of people are TPMT normal metabolizers.
UGT1A1
Uridine diphosphate-glucuronosyltransferase 1A1 (UGT1A1) is the gene that makes an enzyme that processes:
-
cancer medicine—irinotecan
-
HIV medicine—atazanavir
Your UGT1A1 test results will put you in a metabolizer group:
- Poor: The UGT1A1 enzyme has no activity. This means your body processes some medicines very slowly, and you may need lower doses or different medicines.
- Intermediate: The UGT1A1 enzyme has low activity. This means your body processes some medicines more slowly, and you may need lower doses.
- Normal: The UGT1A1 enzyme has normal activity. Your body processes some medicines at an expected rate, and you can use a standard dose of these medicines.
VKORC1
Vitamin K epoxide reductase complex subunit 1 (VKORC1) is the gene that makes an enzyme that helps your blood clot. It affects how your body processes the blood thinner
warfarin.
Your VKORC1 test results will put you in a dose group:
- Normal: The VKORC1 enzyme works as expected. Your body responds to warfarin in a typical way, and a standard starting dose is likely right for you.
- Sensitive: The VKORC1 enzyme is more sensitive than usual. Your body responds strongly to warfarin, and a lower starting dose is likely right for you.
- Most sensitive: The VKORC1 enzyme is very sensitive. Your body responds very strongly to warfarin, and a lower starting dose is likely right for you.
Note: Some test results are indeterminate. An indeterminate result means it’s not known how changes in your genes will affect the way your body processes certain medicines.
