Students preparing for medical school interviews should have a good grasp of various hot topics that can be applied to their answers. QALYs are a very important tool in the NHS and therefore are an important topic to be informed on.
This article looks at what QALYs are, how they are used and calculated, some limitations, ethical considerations, and how to answer questions on them in interviews.
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QALYs: A Summary
A QALY is a Quality-Adjusted Life Year.
QALY = time spent in a particular health state x Health-Related Quality-of-Life score
QALYs are used in the calculation of the cost-effectiveness of treatments.
There are several limitations of QALYs which you must learn about.
You need to understand what QALYs are, how they are used, and some ethical considerations for your medicine interviews.
QALYs are used in the assessment of treatments for certain conditions.
How Are QALYs Calculated? The QALY Formula
The QALY Formula: QALYs are calculated by multiplying the time spent in a particular health state by the HRQL score.
QALY = time spent in a particular health state x Health-Related Quality-of-Life score
What is the HRQL score?
In practice, the most widely used tool in the UK for generating this quality-of-life (utility) weight is the EQ-5D questionnaire. It asks patients to rate themselves across five dimensions: mobility, self-care, usual activities, pain or discomfort, and anxiety or depression. These responses are then converted, using a value set based on public preferences, into a single utility score anchored on a scale where 1 represents perfect health and 0 represents a state equivalent to death. Some severe health states can even score below 0, meaning they are considered worse than death.
You will not be expected to perform this conversion in an interview, but knowing that NICE relies on a standardised, patient-reported measure like the EQ-5D shows genuine depth. It also sets up one of the key criticisms: a single number can never fully capture how an individual patient experiences their own illness.
The HRQL score is the Health-Related Quality-of-Life score. It is a subjective score which looks at how a patient views their health and quality of life.
There are a few different ways to calculate the HRQL score, however, you would not be expected to know this for an interview.
QALYs are used in the assessment of medical treatments by the National Institute for Health and Care Excellence (NICE). NICE is the body that provides national guidance on health and social care in England, and its technology appraisals are also adopted across much of the wider UK.
QALYs can be used alongside the cost of treatment so that NICE can conclude whether a new treatment should be approved for a condition. It will determine the cost per QALY gained for any new treatments to decide whether it is cost-effective to approve it.
NICE has historically considered treatments costing less than £20,000 per QALY gained as cost-effective, with treatments up to £30,000 per QALY potentially approved depending on factors such as the certainty of the evidence and the benefit to patients. Importantly, from April 2026 this standard threshold rises for the first time in over 25 years to a range of £25,000 to £30,000 per QALY gained, the first increase since the threshold was set. For rare and very rare conditions assessed through the Highly Specialised Technologies (HST) programme, a much higher threshold of £100,000 per QALY (rising to as much as £300,000 per QALY for the largest health gains) is used.
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The NICE Severity Modifier (and the End-of-Life Criteria It Replaced)
A common update that many candidates miss is the NICE severity modifier, introduced in 2022. It replaced the older end-of-life criteria, which had given extra weight only to treatments extending life in the final months for people with short life expectancy (a rule that mostly benefited some cancer drugs).
The severity modifier is broader and fairer. It allows NICE to apply a higher QALY weighting to treatments for the most severe conditions, judged by how many QALYs patients lose compared with the general population (the absolute and proportional QALY shortfall). A condition can attract a weight of 1.0 (no uplift), 1.2, or 1.7. In effect, this raises the cost-effectiveness threshold for severe conditions to around £36,000 per QALY at the 1.2 weight and around £51,000 per QALY at the 1.7 weight.
In my experience as a GP, this is a strong point to raise in an interview: it shows NICE has actively tried to address the criticism that a flat threshold treats a mild condition and a devastating one as equally deserving of funding. It demonstrates that the system evolves in response to ethical concerns.
The concept of Quality-Adjusted Life Years (QALYs) plays a significant role in the allocation of healthcare resources.
QALYs provide a standardised measure that combines both the quality and the quantity of life to evaluate the value of different health interventions. This methodology allows health economists and policymakers to prioritize resources, aiming for maximum health benefits per unit of expenditure.
For example, if two treatments cost the same, but one yields more QALYs, resources would be allocated to that treatment.
However, the use of QALYs in resource allocation also raises ethical questions. It implicitly values younger or healthier individuals higher, as they can potentially gain more QALYs from an intervention.
Moreover, treatments for rare diseases often have high costs per QALY, leading to dilemmas in their funding. Despite these concerns, QALYs remain a crucial tool for objective comparisons in healthcare resource allocation.
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An example scenario is included here to aid your understanding of QALYs. However, you don’t need to know how to do this for your medicine interviews.
The QALY Calculation
A patient is suffering from a chronic health condition and takes medication A. On this current treatment, the patient is expected to live for 10 years.
However, this condition affects the patient’s quality of life and has reduced it to 60% of what someone in full health would experience.
Therefore, medication A gives the patient 10 x 0.6 = 6 QALYs. In other words, the patient receives the equivalent of 6 years in perfect health from the medication he is currently on for his condition.
A new treatment - medication B - becomes available for the patient’s condition which minimises their symptoms almost entirely. Their quality of life would increase to 90% of what someone in full health would experience. Therefore, medication B would give the patient 10 x 0.9 = 9 QALYs.
The new treatment would give the patient a net gain of 3 QALYs.
Cost-effectiveness using QALYs (ICERs)
As demonstrated above, medication B gives patients an extra 3 QALYs.
This can be used to calculate how cost-effective the new medication is.
Medication B costs £33,000 more than medication A.
Therefore, 33,000/3 = £11,000 per QALY. This is the Incremental Cost-Effectiveness Ratio (ICER).
Medication B would therefore likely be deemed cost-effective.
However, it is important to be aware that QALYs are not the only parameter used in cost-effectiveness calculation.
It is important that you learn the limitations of using QALYs to help answer questions in your medicine interviews.
Quality of Life is hard to quantify. Many patients will value things like mobility differently from others and thus it is difficult to standardise any scales on quality of life.
There are issues with the way QALYs are calculated. In terms of QALYs, 6 months of perfect health is the same as 1 year experiencing a quality of life reduced by 50% (as both calculations would equal 0.5). It is unlikely that many patients would see these two scenarios as equal.
QALYs view all people as the same. It does not take into account the characteristics of patient groups. Therefore, QALYs will not help with existing health inequities that affect certain patient groups, as the characteristics of the group would not be identified in the QALY calculation.
A valid “cost-effective” threshold is very difficult to establish, especially as some treatments may have positive effects on patients that cannot be grasped by the QALY calculation.
QALYs are used to give patients access to new treatments for their conditions, which is a positive for patients.
However, QALY calculations can also restrict new treatments. A drug may positively impact a patient group’s quality of life, but if it is too expensive, it may not be approved by NICE. This means that patients would not be able to get this treatment on the NHS.
An example of how patient groups can be negatively impacted by QALYs and cost-effectiveness calculations is NICE’s refusal to approve Orkambi for the treatment of cystic fibrosis.
Orkambi was found to greatly improve the quality of life of people with cystic fibrosis, but NICE originally rejected it in 2016 because its cost per QALY (estimated at between £218,000 and £349,000) was far above the threshold. After years of campaigning and an interim access deal in 2019, NICE finally recommended Orkambi, Kaftrio and Symkevi for routine NHS use in July 2024 once the manufacturer Vertex agreed a confidential pricing deal. As of 2026 these drugs are permanently funded, but the long delay shows how cost-per-QALY decisions can hold up access to effective treatments for years.
Ethical Considerations of QALYs (Autonomy, Justice, Beneficence)
It is important to understand the ethical considerations of QALYs and be able to discuss these in your medical interviews.
Autonomy: The use of QALYs in the assessment of treatment options for conditions does restrict the autonomy of patients, as some treatments can be refused because of their ICER.
Non-maleficence/beneficence: Whilst QALY/ICER calculations can approve drugs for patients and thus improve their quality of life, these measurements also lead to drugs getting restricted that would otherwise positively affect patients.
Justice: It can be argued that patients are not viewed fairly by the QALY measurement, as it assumes that a life of better quality is of more value.
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You need to have an understanding of what QALYs are and how they are used. They are great to bring into question topics such as resource allocation and the economic side of the NHS.
You do not need to know every single detail of QALYs for your interviews. Being familiar with what they are, how they are used in simple terms and some ethical considerations will be enough to demonstrate your understanding in interviews. It might be good to reference in questions on organ donations, or questions on ‘who would you give this liver to’ etc.
What are some advantages of using QALYs in healthcare?
What are some concerns or limitations of using QALYs in healthcare?
How does the concept of QALYs support the ethical principle of distributive justice within healthcare?
In your opinion, how well does the use of QALYs align with the core values of the NHS, such as comprehensive service provision and responsiveness to individuals' health needs?
Can you discuss a scenario in which QALYs might not be an effective measure for determining the worth of a healthcare intervention, and suggest potential alternatives?
(Hard) How might the quality of life be hard to quantify?
How might a treatment benefit a patient in ways that aren’t included in quality-of-life calculations?
Q: What are some advantages of using QALYs in healthcare?
A: QALYs, or quality-adjusted life years, are used to analyse the effect of a new treatment on someone’s quality of life. The scores generated are then used to calculate the cost-effectiveness of the new treatment.
One advantage of using QALYs is that it is a quantitative figure, and therefore they can be compared easily. Furthermore, quantitative data can tell us lots of information within a number, so is more efficient.
Another advantage of using QALYs is that the calculation used to calculate them is simple. Therefore, it makes the calculation of QALYs more accessible and many people can use them.
Lastly, the use of QALYs allows cost-effectiveness to be more patient-centred. Instead of NICE disregarding new treatments because they cost too much, the treatment’s effect on the quality of life is calculated and incorporated into this to conclude cost-effectiveness.
Therefore, there are benefits to the use of QALYs in medicine.
QALYs are an important topic for students to understand and can be a great tool to use in interviews to demonstrate an understanding of how the NHS deals with resource allocation.
QALY stands for Quality-Adjusted Life Year. It is a measure used in health economics that combines both the length of life and the quality of that life into a single number. One QALY equals one year of life lived in perfect health, which makes it possible to compare very different treatments on a common scale.
What is a QALY in simple terms?
In simple terms, a QALY is a way of measuring how much a treatment improves both how long and how well someone lives. One QALY equals one year in perfect health. If health is less than perfect, the score is below 1. For example, one year lived at 50% of full health counts as 0.5 QALYs.
What is the QALY formula?
The QALY formula is: QALYs = years of life gained x utility weight (the quality-of-life score). The utility weight runs from 0, representing death, to 1, representing perfect health. So a treatment that gives a patient 10 years of life at a quality score of 0.8 produces 10 x 0.8 = 8 QALYs.
How do you calculate a QALY?
To calculate a QALY, multiply the number of years a person is expected to live by their quality-of-life (utility) score on a scale of 0 to 1. For example, a patient expected to live 5 years at a quality of life of 0.6 gains 5 x 0.6 = 3 QALYs. To assess a new treatment, you compare the QALYs it produces against the existing option.
What is an example of a QALY calculation?
Imagine a patient with a chronic condition expected to live 10 more years at a quality of life of 0.6, giving 10 x 0.6 = 6 QALYs. A new drug raises their quality of life to 0.9, giving 10 x 0.9 = 9 QALYs. The new drug therefore delivers a net gain of 3 QALYs, which can then be weighed against its extra cost.
How does NICE use QALYs?
NICE uses QALYs to judge whether a treatment is cost-effective for the NHS. It calculates the cost per QALY gained, known as the Incremental Cost-Effectiveness Ratio (ICER), by dividing a treatment's extra cost by the extra QALYs it produces. This figure is then compared against NICE's cost-effectiveness threshold to inform funding decisions.
What is the NICE cost-effectiveness threshold per QALY?
NICE has historically regarded treatments costing under £20,000 to £30,000 per QALY gained as cost-effective. From April 2026 this standard threshold rises to roughly £25,000 to £30,000 per QALY, its first increase in over 25 years. Highly Specialised Technologies for rare diseases use a much higher threshold of £100,000, rising to as much as £300,000 per QALY for the largest health gains.
What is the NICE severity modifier?
The severity modifier, introduced by NICE in 2022, replaced the older end-of-life criteria. It lets NICE give extra weight (1.2x or 1.7x) to QALYs from treatments for the most severe conditions, judged by how much health patients lose compared with the general population. This effectively raises the threshold to around £36,000 or £51,000 per QALY for severe conditions.
What is an ICER?
ICER stands for Incremental Cost-Effectiveness Ratio. It is the extra cost of a new treatment divided by the extra QALYs it provides compared with the current treatment. For example, if a new drug costs £33,000 more and delivers 3 extra QALYs, its ICER is £11,000 per QALY. NICE compares the ICER against its threshold to decide on funding.
How is quality of life measured for a QALY?
Quality of life is measured using a utility score from 0 (death) to 1 (perfect health). In the UK the most common tool is the EQ-5D questionnaire, which asks patients about mobility, self-care, usual activities, pain or discomfort, and anxiety or depression. These answers are converted, using public preference values, into a single utility weight used in the QALY calculation.
What are the limitations and criticisms of QALYs?
Key criticisms are that QALYs can discriminate against older and disabled people, who may have fewer potential QALYs to gain; that quality of life is subjective and hard to standardise; and that the maths can feel unfair (one year at half quality scores the same 0.5 as six months of perfect health). Critics also argue a single number cannot capture every benefit a treatment brings.
Are QALYs ageist or discriminatory against disabled people?
This is a serious criticism. Because QALYs reward larger gains in length and quality of life, younger and healthier people can appear to benefit more, and a disabled person who starts from a lower baseline may generate fewer QALYs. NICE's severity modifier partly addresses this by giving extra weight to severe conditions, but the underlying ethical concern about distributive justice remains widely debated.
What is the difference between a QALY and a DALY?
A QALY (Quality-Adjusted Life Year) measures health gained, where higher is better and 1 equals a year of perfect health. A DALY (Disability-Adjusted Life Year) measures health lost, where lower is better. DALYs combine years of life lost to early death with years lived with disability, and are mainly used to measure the overall disease burden in a population.
Why are QALYs important in medicine?
QALYs are important because they give the NHS a standardised, objective way to compare very different treatments and decide where limited resources do the most good. By combining length and quality of life into one figure, they let NICE prioritise treatments offering the greatest health benefit per pound spent, which is essential for fair and sustainable resource allocation.
How should I use QALYs in a medicine interview?
Explain a QALY simply (one year of perfect health), show you understand how NICE uses cost per QALY to decide funding, then demonstrate balance by discussing both benefits (objective, comparable, patient-centred) and criticisms (potential ageism, subjectivity). Bonus depth comes from mentioning the 2022 severity modifier and the changing NICE threshold. QALYs link naturally to questions on rationing, resource allocation and ethics.
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