Why does a new medicine lead to more blood tests?
Longetic keeps lab reports from different clinics in one record, which matters here because a monitoring result is only readable next to the one that came before it. In England, NHS England publishes that requesting blood tests is a clinical responsibility, and that patients must be made fully aware of all monitoring requirements. In Spain, the instruction usually sits inside the patient leaflet of the medicine itself, authorised by the national medicines agency.
A prescription is not always the end of the appointment. For a good number of medicines, starting one is the beginning of a schedule of blood tests that belongs to that medicine, and the schedule can outlast the reason you remember for taking it. Who orders those tests is published plainly. NHS England's guidance on prescribing responsibility between primary and secondary care, version 1.0, first published in January 2018, prints the line "Clinical responsibility for prescribing is held by the person signing the prescription". The same document prints, as its own separate clause, "who must also ensure adequate monitoring".
The same document is unusually direct about your side of it. It prints "patients must be made fully aware of all monitoring requirements", and separately "All appropriate monitoring requirements must be fulfilled." A second NHS England document, on optimising blood testing in primary care, dated 16 September 2021, prints "Requesting blood tests is a clinical responsibility and sits with the assessing clinician." We are quoting that one line and nothing else from it, because the rest of that document was written for a specific supply situation in 2021 and its intervals are not standing guidance. If several people prescribe for you, the question of who is tracking what becomes its own problem, and we have written about keeping one medication list when several people prescribe for you.
Does every medicine need the same tests?
No, and the official sources are structured around that fact rather than around a single rule. The NHS Specialist Pharmacy Service publishes a separate monitoring page for each medicine: one of those pages says that no routine monitoring of its kind is needed at all, and another publishes a list of tests to be done before starting and a schedule of repeat tests afterwards. Spain shows the same shape inside each medicine's own leaflet.
The Specialist Pharmacy Service states who it is written for, and it is worth reading that line before reading anything else on it: "Our content is intended for use by NHS healthcare professionals in England". It is a professional reference. A patient reading it is reading over a clinician's shoulder, which is allowed and often useful, but it is not a patient leaflet and it does not pretend to be one.
Its page on direct oral anticoagulants, last updated 6 August 2026, prints "No routine anticoagulation monitoring is needed for DOACs". Its page on methotrexate, published 5 July 2021 and last updated 7 January 2026, instead sets out tests to be done before starting and a schedule of repeat tests that continues while the medicine does. We are deliberately not reprinting the intervals from either page. Intervals are set for a person by the clinician who ordered them, and a number lifted out of a professional reference and into an article stops meaning what it meant. Every one of those pages carries the same line at the top: "It is designed to save clinician time, but not replace professional responsibility." Reading only the first half of that sentence is the common mistake.
Spain puts the same information somewhere else. The patient leaflet for methotrexate authorised by the Agencia Española de Medicamentos y Productos Sanitarios, whose printed revision line reads "Fecha de la última revisión de este prospecto: octubre 2026", prints "Antes de iniciar el tratamiento y mientras esté en tratamiento con metotrexato, su médico le puede realizar pruebas". Note "le puede realizar", may rather than will. The leaflet for paracetamol, revised in February 2025, publishes no monitoring schedule at all. Same country, same document class, same regulator, different medicine, different answer.
| Source | Country | Written for | What it publishes per medicine |
|---|---|---|---|
| NHS Specialist Pharmacy Service | England | Healthcare professionals | A separate monitoring page per medicine |
| nhs.uk medicine pages | England | Patients | Monitoring on some medicine pages, not all |
| AEMPS patient leaflet | Spain | Patients | Monitoring inside each medicine's own leaflet |
| Red de Escuelas de Salud | Spain | Patients and carers | Who self-tests, by type of treatment |
What do the patient pages in England actually say?
Some of them say it plainly, and some say nothing. The medicine pages for lithium, methotrexate, warfarin and ramipril each tell the reader that tests will follow, with wording that ranges from will to may, while the general page about blood tests on the same site does not say it at all. Whether you were told, in other words, depends on which page you happened to land on.
The ramipril page, reviewed on 18 March 2026 with its next review due on 18 March 2029, prints "You may also have blood tests to check how well your kidneys are working and the amount of potassium in your blood." The word is may. The warfarin page, reorganised and reviewed on 24 February 2026, prints "While you're taking warfarin, you'll need regular blood tests to measure how quickly your blood clots." and then "This is called an international normalised ratio (INR) test." The methotrexate page carries a section headed "Tests during treatment" and explains "These tests are to check if the methotrexate is working and if it's causing any side effects."
Now the gap. The general blood test page on the same site lists reasons a test may be done, including "find out how well a condition is being treated or managed", and it asks the reader about "any medicines you're taking." Across that page we found nothing telling a reader that starting a medicine brings repeat tests of its own. That is a statement about one page, which is the only kind of statement we are willing to make: we read it on 22 October 2026 and we are describing what was on it.
One more thing about those pages, and it is awkward. Of the four medicine pages we read that carry the monitoring message, two were already past their own printed review date on the day we checked: methotrexate prints "Next review due: 14 March 2026" and lithium prints "Next review due: 9 August 2026". The warfarin page had been restructured since earlier versions, and an older address for it no longer opens. The general blood test page prints "Next review due: 02 November 2026", which falls within days of this article. None of that makes the content wrong. It does mean that if you are reading this months from now, the page may have moved underneath the quotation, and the date on the page is the thing to check first.
What does Spain publish, and at which level of the system?
At national level, the Ministry of Health's citizen network publishes that whether you test yourself at all depends on what you are being treated with, and that the professionals in charge of your care are the ones who set the number of tests. Below that level the picture is regional, and a regional instruction is not a Spanish one. Galicia's health service publishes its own wording for people on anticoagulants.
The Red de Escuelas de Salud para la Ciudadanía is the Ministry of Health's patient-facing network. Its page on type 2 diabetes prints "Sólo las personas que se inyecten insulina o tomen pastillas que puedan bajar la glucemia deben realizar autoanálisis.", which says that only people on certain treatments need to self-test. On who decides how much testing happens, the same page prints "Son los/las profesionales encargados de su cuidado quienes deben indicarle el número de pruebas". The page's source line reads "Red de Escuelas 25/02/2014" and its footer reads "Copyright © Ministerio de Sanidad 2021", so it is a national page that has been standing for some time.
Below national level, the wording is a regional author's. The Servizo Galego de Saúde, the health service of Galicia, prints for people on anticoagulants "Los análisis de control son la única forma de conocer la dosis que precisa cada paciente." and "No falte al control el día y a la hora que le indiquen." That page prints no date of its own. It is Galicia speaking, and we are not going to turn it into Spain speaking, because the pattern in this project has been consistent: one Spanish region's instruction routinely differs from the next one's.
There is one national Spanish document about control tests that we are deliberately not quoting as advice to you. The Ministry of Health's "5 Momentos Clave" dossier, dated Marzo 2022, prints "Esta guía para los profesionales sanitarios se ha basado en los 5 Momentos Clave para". It is a guide for health professionals, and its instructions, including "Indicarle si es preciso que le hagan alguna prueba de control.", are instructions to a clinician about what to tell you. That is a real difference, and quoting it as if the ministry were addressing patients would misreport the document.
Who is actually told to keep the results?
England tells some patients to keep a record, and even names the booklet it arrives in. Spain's national patient material tells you to keep a list of your medicines, which is a different object entirely. Across the national Spanish pages read for this article, not one asked the patient to keep a copy of the blood test; the closest instruction came from a territorial leaflet, and it asked for the most recent one.
The methotrexate page on nhs.uk prints "It's important to record how much methotrexate you take and the results of your blood tests." and adds "You'll usually get a booklet for this." The lithium page goes further: "you'll get a lithium treatment pack (usually a purple folder or book) with a record booklet.", and then "You need to show your record booklet every time you see your doctor, go to hospital, or collect your prescription." So the idea that your results are worth holding onto is already official in England. It just arrives attached to particular medicines rather than as a general habit.
Spain's national patient material asks for something adjacent but not the same. The Ministry of Health's citizen safety campaign prints "Realiza una lista de los medicamentos que tomes". Its page on preparing for a medical appointment prints "Haga una lista de todos sus medicamentos y pastillas", with "o llévelos consigo" as a separate fragment offering an alternative rather than an addition. Both are about medicines. Neither is about results. Across the national Spanish pages read for this article, we found none asking the patient to keep a copy of the analítica. The nearest came from an INGESA leaflet written for Ceuta, which, for patients travelling abroad, prints "lleve el informe médico donde aparece su tratamiento" and, as its own separate fragment, "además de su hoja del último control". The latest control sheet, not the first one.
| What you are asked to keep | England | Spain, national level |
|---|---|---|
| A list of your medicines | Yes, on the appointment page | Yes, in the citizen campaign |
| A record of your test results | Yes, for some medicines, in a booklet | Not found in the pages we read |
| The result from before you started | Not found in the pages we read | Not found in the pages we read |
Where did the first result go?
The professional word for it is baseline, and it lives almost entirely on the professional side of the system. It appears on Specialist Pharmacy Service pages and in NHS England documents, but on none of the patient pages read for this article. When the idea does reach a patient, it usually arrives in plainer words: before starting treatment.
Here is the word doing its actual job, on a professional page about mycophenolate: "Creatinine increase greater than 30% above baseline over 12 months". That is baseline as a comparator. The number after only means something because a number before exists to compare it with. And here is the closest the idea gets to being said to a patient, from a Medicines and Healthcare products Regulatory Agency drug safety update published on 15 March 2022 and last updated on 20 May 2026: "your doctor may perform tests of your blood, lungs, heartbeat, and eyes before and during treatment". Before and during, in one phrase, addressed to the reader.
Which raises a practical problem that the NHS itself prints. Its page on test results in the NHS App, reviewed on 13 January 2026 with the next review due on 13 July 2027, states "It is not possible to download your test results from the NHS App." The same page says "Contact your GP surgery if you need a copy of your test results or health record." On the graph that would show one test over time, it prints "A graph will only be available if the same test has been done at least twice in the past 3 years" and "This feature is not available for all users, it depends on your GP surgery." Both qualifiers are load-bearing. We are not making any claim here about results from private providers, which is a separate subject.
One caution before anyone starts comparing numbers at home. Two results for the same marker are not automatically the same measurement, and the reasons have nothing to do with you: a laboratory can change its method, its units or its own reference interval between one test and the next. We have written separately about why two lab reports may not be the same measurement, and about how two lab results show a change, three show a trend. Keeping the first result is what makes any of that conversation possible with your doctor. It is not the same as having the conversation yourself.
What is worth writing down?
Four things, and not one of them is an interpretation: the date and the laboratory of the test done before the medicine started, the date of every test since, and the name and the strength of the medicine exactly as printed on the box. The fourth is who ordered the test, because the clinic that ordered it is the one holding the result, and that is where a copy has to be requested from.
Write the dates down the way the paperwork does, not the way you remember them. The test that came before the medicine is the one most likely to go missing, because at the time it did not look like the beginning of anything. If you have the printed report, the laboratory's own reference interval is printed beside each value, and that interval belongs to that laboratory rather than to the number. Keep them together. If you were told how often the next tests are due, write down who told you and when, so the answer does not have to be reconstructed from memory at the next appointment. For the appointment itself, we keep a short list of what to write down before a doctor's appointment.
This is the part Longetic is built for. It keeps lab reports from different laboratories in one record and shows each biomarker's value next to your lab's own reference range, and it holds your medicine list with reminders and a dose schedule, so the date you started something and the report that came before it end up in the same place rather than in two different email threads. What it does not do is worth being equally plain about: it does not interpret a result, it does not convert units, it does not check interactions between medicines, it does not read an NHS GP record, and it has no NHS login. If a document is in a layout or language it cannot read, it stays in your record as a file, so nothing is lost.
None of this is a reason to ask for a test, to skip one, or to change anything you are taking. The useful version of this article is much smaller than it looks: when a medicine starts, a result from before it started becomes worth keeping, and almost nobody will tell you so at the time.
