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CION Cancer Clinics
Intermediate metaboliser results and how the dose is adjusted | CION Cancer Clinics
An intermediate metaboliser result means one gene processes certain medicines more slowly than usual, but not as slowly as in a poor metaboliser. Usually you have one working copy and one faulty copy. For some drugs this means a lower starting dose that can be raised if you cope well. For others it changes nothing. This page explains the difference, gene by gene, and how the dose is adjusted. At CION Cancer Clinics, our team helps carriers and their families plan checks, next steps and support after a genetic result.
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Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed September 2026, next review due September 2027
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On this page
- What does an intermediate metaboliser result mean for my dose?
- How does an intermediate result change the dose for each gene?
- How is the dose adjusted over the first few cycles?
- The words around an intermediate result, in plain language
- How is intermediate different from poor?
- What this page cannot tell you
- Four things people assume about an intermediate result
- Common questions about intermediate metaboliser results
The short answer
What does an intermediate metaboliser result mean for my dose?
It means one gene processes certain medicines at reduced strength, usually because you have one working copy and one faulty copy. For some drugs, the starting dose is lowered and then raised if you cope well. For others, the result changes nothing at all. Which applies depends entirely on the gene and the drug.
A starting point, not a fixed dose
The lower starting dose is a safety step. It protects you in the first cycle, when nobody yet knows how your body will respond. If blood tests and side effects stay manageable, many teams raise the dose in later cycles. The aim is the fullest dose you can safely take, not the smallest one.
Why intermediate is harder to predict than poor
People with a poor result all clear the drug very slowly, so the advice is firm. The intermediate group is wider. Some behave almost normally, and some come close to the poor group. That spread is why your response in the first cycle often tells the team more than the label itself. Other medicines you take can also push you towards the slower end.
An intermediate result is a reason to start carefully. It is not a reason to avoid treatment.Gene by gene
How does an intermediate result change the dose for each gene?
The same word leads to very different advice depending on which gene it sits beside.
DPYD
Before fluorouracil or capecitabine, guidelines advise starting at about half the usual dose. If the first cycle goes well, the dose is raised step by step. This is the result where the change matters most.
What you will notice
- A lower first-cycle dose on the chart
- Closer checks in the early weeks
- A review before each dose increase
TPMT or NUDT15
Before mercaptopurine or other thiopurines, the starting dose is set below the usual level. Blood counts then guide it up or down, as they do for every patient on these tablets.
UGT1A1
One slow copy usually means no change to the standard starting dose of irinotecan. Some teams watch the first cycle a little more closely for diarrhoea and low counts.
CYP2D6
For tamoxifen, the evidence is debated and advice varies between oncologists. For codeine and tramadol, the usual dose is tried first, and a different painkiller is chosen if relief is poor.
Not sure whether this applies to you?
Ask an oncologistCycle by cycle
How is the dose adjusted over the first few cycles?
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Before the first cycle
The oncologist sets a starting dose from your body size, your treatment protocol and the gene result. You should be told if it is lower than usual and why.
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During the first cycle
Blood tests and side effects are watched more closely than usual. Report diarrhoea, mouth sores, fever or sore, peeling hands promptly rather than waiting for the next visit.
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The review before the next cycle
If you coped well and counts recovered, the dose may be raised. If side effects were significant, it is kept the same or lowered further. Either outcome is expected.
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Settling on your dose
After a few cycles, most people reach a dose that suits them. From then on it changes only if something else changes, such as an infection or a new medicine.
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Recording where you landed
Ask for the final tolerated dose to be written in your records. It is useful if the same drug is ever needed again.
On your report
The words around an intermediate result, in plain language
- Intermediate metaboliser
- A gene working at reduced strength. Drugs that depend on it are processed more slowly than usual.
- Heterozygous
- Two different versions of a gene, one from each parent. Most intermediate results mean one working and one faulty copy.
- Reduced function
- A gene version that works, but weakly. Two reduced-function copies can also add up to an intermediate result.
- Activity score
- A number some reports give for DPYD and CYP2D6. Intermediate scores sit between the normal and poor ranges.
- Dose titration
- Raising or lowering a dose in steps, guided by how you respond, until the right level is found.
- Phenoconversion
- When another medicine slows the same enzyme, making an intermediate metaboliser behave more like a poor one.
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Side by side
How is intermediate different from poor?
Intermediate metaboliser
Poor metaboliser
Usually one working copy of the gene
Usually no working copy
Starting dose often lowered
Dose cut sharply, or the drug avoided
Often raised later if you cope well
Usually stays low, or a different drug is used
For some drugs, no change at all
Almost always changes the plan
Being straight with you
What this page cannot tell you
It cannot tell you your dose. That depends on your protocol, your body size, your kidney and liver function and every other medicine you take. What your specific result means is a question for the oncologist or genetic counsellor who ordered the test.
What the evidence does and does not show
For DPYD, studies suggest that a lower starting dose in intermediate metabolisers reduces severe side effects. Whether it changes how well the treatment works has been studied less. Studies in Indian patients are small for most genes, and panels differ in which variants they check.
Who this does not apply to
If your result is normal, or you are not taking a drug linked to the gene, an intermediate label elsewhere on the report changes nothing today. It is not a cancer risk test, and it is separate from tumour tests that guide targeted treatment.
Why your tablet list matters
Some common medicines slow the same enzymes. Certain antidepressants, for example, slow CYP2D6. Bring every tablet, syrup and supplement to your appointment so the team can see the whole picture.
Commonly believed
Four things people assume about an intermediate result
"Intermediate is borderline, so it can be ignored."
For some genes it matters a great deal. Before fluorouracil or capecitabine, a full standard dose can cause serious side effects in some intermediate DPYD metabolisers. That is why the guideline advises a lower start.
"Once the dose is lowered, it stays lowered."
Often it does not. The lower dose is a cautious first step. If you cope well, the team can raise it in later cycles towards the usual level.
"Mild side effects mean the lower dose is not working."
Side effects are not a measure of how well treatment works. A lower dose in a slow metaboliser can give roughly the same drug levels as a full dose in someone else.
"My other tablets have nothing to do with this."
Some everyday medicines slow the same enzymes and can make an intermediate metaboliser behave like a poor one. Always show your full tablet list.
Questions we are asked
Common questions about intermediate metaboliser results
Will my dose be raised later?
Often, yes, if you cope well with the first cycle. The decision is made at each review, based on your blood tests and side effects. Some people stay on the lower dose because it suits them, and that is also a good outcome.
Does an intermediate DPYD result mean I cannot have capecitabine?
No. Guidelines advise a lower starting dose, not avoiding the drug. Most people with this result still receive capecitabine or fluorouracil, with the dose raised if the first cycle goes well. Your oncologist will explain the plan before you start.
Is intermediate metaboliser the same as being a carrier?
Often it means the same thing: one faulty copy and one working copy. Here it describes how you handle certain drugs, not a disease. It carries no cancer risk and needs no treatment of its own.
Which side effects should I report early?
Report diarrhoea, mouth sores, fever, unusual tiredness, bruising or sore, peeling hands promptly. In the first cycle these are the signs that tell the team your dose may be too high. Early reporting lets them adjust before a problem becomes serious.
Can my other medicines change my result?
They cannot change your genes, but they can change how the enzyme works. Some antidepressants, such as paroxetine and fluoxetine, slow CYP2D6. Tell every prescriber about your result and about everything you take.
Should my family be tested?
Not routinely. Your children and siblings may share the result, but it carries no cancer risk. Tell them about it, so they can mention it if a doctor ever prescribes them one of the linked drugs.
The report is confusing. Who should explain it?
Start with the doctor who ordered the test. If they are unsure, ask to see a genetic counsellor or a clinical pharmacologist. Many reports are written for doctors, so needing an explanation is normal.
Will I need the test again for future treatment?
No. Your genes do not change, so the same result applies for life. Keep the report, and a photo of it on your phone, and show it whenever a new medicine linked to that gene is prescribed.
Your Specialists
Meet CION's oncologists. Bring your family history or genetic report to them.
Our medical oncologists see people with a strong family history of cancer, arrange genetic counselling and testing where it fits, and plan the checks that follow.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
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Sources
- Clinical Pharmacogenetics Implementation Consortium (CPIC) — CPIC Guideline for Fluoropyrimidines and DPYD
- Clinical Pharmacogenetics Implementation Consortium (CPIC) — CPIC Guideline for Thiopurines and TPMT and NUDT15
- MedlinePlus Genetics — What is pharmacogenomics?
- US Food and Drug Administration — Table of Pharmacogenomic Biomarkers in Drug Labeling
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
What a poor metaboliser result meansThe slower result, and why its advice is firmerTPMT and NUDT15 before thiopurinesHow intermediate results shape thiopurine dosesUGT1A1 beyond irinotecanWhen one slow UGT1A1 copy matters, and when it does notCarrying your pharmacogenomic result for future careMaking the result follow you to every prescriber
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