No, not as a single, standalone test, at least not yet. There's still no blood test for dementia that gives a definitive diagnosis on its own. But a blood biomarker called p-tau217 can now help detect changes linked to Alzheimer's disease, and the NHS is trialling tests for it at sites across the UK.
Around 982,000 people in the UK live with dementia. Over a third of dementia cases go undiagnosed. If you're weighing up whether to ask a GP about a dementia diagnosis, for yourself or a loved one, this guide covers what p-tau217 is, how blood tests can identify it, and how dementia is still diagnosed while the NHS trials continue. Getting this right matters because an early diagnosis opens the door to support, planning, and, in time, potentially life-changing treatments.
A simple blood test for dementia has long been a goal for researchers. For decades, confirming the proteins linked to Alzheimer's disease meant either a cerebrospinal fluid sample or a brain scan. Both are expensive and not always easy to access. Both can be uncomfortable for patients as well.
The Blood Biomarker Challenge is a £5 million initiative from Alzheimer's Society, Alzheimer's Research UK and the National Institute for Health and Care Research. It aims to improve dementia diagnosis in the UK. TheAlzheimer's Society has described the challenge’s ambition as one that could revolutionise dementia diagnosis nationwide.
The challenge aims to provide fair and equitable access to diagnostic tests that are quicker and cheaper and less invasive than a scan or lumbar puncture. Medical research in this area continues at pace, with new findings published often.
p-tau217 is now considered the most promising biomarker used to help diagnose Alzheimer's disease. It's a form of tau, a protein found in brain and spinal cord tissue. When Alzheimer's-related changes begin, levels of p-tau217 in the blood increase, reflecting the build-up of amyloid and tau in the brain. It's measured by a simple blood sample, rather than a scan or lumbar puncture.
In research, dementia blood tests measuring p-tau217 have shown high accuracy. A 2025 accuracy study of over 1,700 patients found that the p-tau217 blood test correctly identified Alzheimer’s-related pathology in 89-91% of patients receiving specialist care, using cerebrospinal fluid results and PET scans as reference standards.
. That means this new blood test for dementia has an accuracy close to older, more invasive diagnostic tools. It's now one of the main tests for diagnosing Alzheimer's, moving from research into wider practice.
A few important points for context. A positive test does not mean a definitive diagnosis on its own, and it isn't used to diagnose Alzheimer's by itself either. p-tau217 is used alongside a medical history, cognitive tests, and sometimes a brain scan, not instead of them, and a raised result can lead to further testing. It's for people who already have memory and thinking problems, not for screening people with no symptoms. Blood tests generally cannot reliably predict whether a healthy person will develop dementia with certainty.
Not yet, as a routine test. Blood tests for dementia are not yet available in the NHS as standard, but they are further along than most people realise. Two major UK trials are under way.
ADAPT, led by Professor Jonathan Schott and Dr Ashvini Keshavan at University College London, is testing whether giving memory clinic patients their p-tau217 result leads to an early and accurate diagnosis. It's running in around 20 NHS centres, in clinical settings, backed by Alzheimer's Research UK and Alzheimer's Society.
READ-OUT, led by Dementias Platform UK researchers at Oxford and Cambridge, will test multiple existing and new blood biomarkers across various stages of several dementia types, including vascular dementia and frontotemporal dementia, a rare form of the condition. The first participants for the READ-OUT study were recruited in January 2025.
Both trials are being run under the Blood Biomarker Challenge, which aims to bring blood tests into routine NHS care later this decade. Separately, in the US, the first p-tau217 test was FDA-cleared in 2025 for use alongside other medical tests, and the Alzheimer's Association has since published its own clinical guidance for doctors. However, the test is not yet routinely available on the NHS. For now, if you're worried a loved one may have dementia, speak to a GP for advice.
Today, dementia is diagnosed using a combination of established methods, alongside a review of the patient’s medical history. While blood tests move through clinical trials, these methods remain the gold standard for diagnosis.
Brain scans help rule out other conditions causing dementia symptoms and let doctors see physical changes in the brain linked to cognitive decline.
The cerebrospinal fluid surrounds the brain and spinal cord. A lumbar puncture (spinal tap) allows specialists to test spinal fluid for key proteins.
Low beta-amyloid 42 can suggest Alzheimer's-related build-up in the brain. High tau and phospho-tau point to damage inside brain cells. These spinal fluid tests remain highly accurate, though they're more invasive than a blood draw.
Beyond p-tau217, researchers are validating several other Alzheimer's blood biomarkers. Amyloid-beta proteins form sticky amyloid plaques in the brain. Monitoring them is central to several of these tests. The amyloid-beta ratio tracks the misfolded proteins that accumulate in Alzheimer's disease. A lower amyloid-beta ratio indicates a higher likelihood of amyloid plaques and thus Alzheimer’s.
Phosphorylated tau forms tangles in the brain and rises in blood in early Alzheimer's disease, which is why it's so useful for detection. These biomarkers help differentiate Alzheimer's disease from other causes of cognitive decline. Neurofilament light chain is a protein that leaks into the bloodstream when brain cells are damaged, reflecting general brain health rather than one specific disease. Glial fibrillary acidic protein is a marker of brain inflammation associated with neurodegenerative diseases.
Genetic testing is a separate approach used where there's a strong family history of Alzheimer’s. Some biomarkers may also help estimate a person's risk of developing dementia, which is different from assessing someone who already has cognitive problems.
Blood tests do not diagnose dementia by themselves but indicate biological changes associated with brain diseases. Blood tests can also determine whether a patient with mild cognitive impairment needs a specialist referral. Blood tests have lower costs and higher accessibility than traditional methods for detecting dementia. That said, many blood tests require further validation to establish their accuracy and reliability in diverse populations, which is exactly what the ADAPT and READ-OUT projects are working on.
If you're concerned about dementia symptoms, either your own or a loved one's, the first step is your GP. Not sure whether what you've noticed fits the pattern? Our early signs of dementia guide runs through what's worth mentioning at that appointment.
Your GP will ask about your medical history, any memory loss you've noticed, and how these memory problems affect daily life. It often helps to bring a family member along. Your GP will usually check your blood pressure, order standard blood tests to rule out vitamin deficiencies or thyroid issues, and may use simple memory tests such as the Montreal Cognitive Assessment.
If other causes are ruled out, your GP may refer you to a specialist at a memory clinic, such as a geriatrician, neurologist, or psychiatrist. The specialist will assess symptoms of dementia, run more detailed cognitive assessments covering mental abilities such as memory, attention and language,and may arrange brain imaging to investigate changes in brain function.
Over a third of dementia patients in England remain undiagnosed. The diagnosis pathway can take a long time to complete. Alzheimer's Society's most recent analysis, published in May 2026, found people wait on average three and a half years from first noticing symptoms to a formal diagnosis, including several months after a GP referral to a memory clinic.
An earlier Alzheimer's Society survey found more than half of people (56%) wait a year or more before even seeking a diagnosis in the first place. An accurate diagnosis lets you understand what's happening and plan ahead, and opens the door to support and, where appropriate, treatment.
So, is there a blood test for dementia you can get today? Not as a standalone, walk-in test, but the picture is changing quickly, especially for the early stages of Alzheimer's disease, when a diagnosis matters most. p-tau217 is the most promising biomarker we have for Alzheimer's disease. NHS trials are under way, but the test hasn’t been rolled out to the wider public yet. For now, the most reliable path to a diagnosis includes cognitive tests and brain scans.
At Tiggo Care, we understand the impact a dementia diagnosis has on a family. Our dementia home care service is built around each person, helping with medication routines, meal preparation, and escorting to social events and appointments. If you'd like to understand more about what dementia care at home involves, or want to catch up on the latest dementia treatment news, check out our dedicated guides.
For guidance on costs, get in touch, and we'll talk you through a plan and pricing built around your loved one's needs. We're regulated by the Care Quality Commission, meaning our care is regularly inspected to ensure it's safe, effective, caring, responsive and well-led. We're members of the Homecare Association and recognised by homecare.co.uk and Age UK. Contact Tiggo Care today to talk about arranging care for your loved one.
Chris Williams is the Founder and Managing Director ofTiggo Care, an award-winning London home care provider that supports adults living in their own homes. He founded Tiggo Care after struggling to find suitable care for his parents, both of whom lived with rare diseases, giving him first-hand experience of the challenges families can face when arranging personalised home care. Chris studied Human Sciences and Epidemiology at Oxford University and previously worked at Kearney and Oxford Sciences Enterprises.
Not on its own, but blood tests measuring biomarkers like p-tau217 can now detect Alzheimer's disease-related changes with high accuracy. This new blood test for dementia is currently being trialled and may be rolled out to the public in the next few years. Such tests are used alongside a medical history and cognitive assessments, and are moving from research into clinical settings.
Not routinely, not yet. The NHS is trialling p-tau217 through ADAPT and READ-OUT, with a view to wider use later this decade. If you're worried about memory problems, the first and best step is still a GP appointment.
In research, p-tau217 has shown accuracy generally around 90% for identifying Alzheimer's disease-related changes, close to a PET scan. It works best as part of a wider assessment, not as a standalone positive test.
When you first see a GP with memory concerns, they'll order standard blood tests to rule out other causes, like thyroid problems or vitamin deficiencies, not to detect dementia itself. Specialist tests like p-tau217 exist but aren't yet routinely available.
Early diagnosis allows access to new treatments and clinical trials, plus support services and counselling. It also gives people and their families time to plan ahead. Early diagnosis can improve quality of life for patients and families. New drugs for early-stage Alzheimer's are expected soon, though the newest ones aren't currently funded on the NHS, so it's worth asking a GP what's available to you now.
Yes. Tiggo Care provides professional home care for people living with dementia. Our care assistants help with personal care, medication routines, domestic tasks, and companionship, with an individualised care plan focused on maximising quality of life for your loved one.
Get in touch with Tiggo Care today to see how we can help you or your loved one.
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