SOLK: what the diagnosis means and what investigation precedes it

SOLK is the Dutch abbreviation for Somatisch Onvoldoende verklaarde Lichamelijke Klachten: physical symptoms that are insufficiently explained. The label means your symptoms have lasted longer than a few weeks and that adequate medical investigation found no condition that explains them well enough. In general practice, 40 to 49 percent of people report at least one physical symptom without an adequate explanation (PMID 25939319).

One word in that abbreviation gets skipped almost every time: insufficiently. It describes the explanation, not you. Your symptoms are genuinely there.

That difference is not cosmetic, and it is exactly where this label goes wrong in practice. Thuisarts, the Dutch GP patient portal, says it in four words: "U verzint het niet." You are not making it up.

Below I explain what the diagnosis does and does not say, why the term is shifting to ALK, and what investigation usually precedes it.

What does SOLK actually mean?

SOLK means your physical symptoms have lasted longer than a few weeks, while adequate medical investigation has not produced a condition that explains them well enough. So it is a conclusion after investigation, not a starting point. And it says nothing about whether your symptoms are real, only about the state of the explanation right now.

That order matters. The NHG, the Dutch college of general practitioners, describes SOLK as symptoms lasting longer than a few weeks where adequate medical investigation found no condition that sufficiently explains them. The word adequate is doing real work there.

SOLK is not a bin for symptoms nobody wants to look at any more. It is a conclusion that only follows once someone has looked.

Thuisarts sums it up for patients like this: "Uw huisarts heeft u onderzocht en er is geen lichamelijke oorzaak voor uw klachten te vinden." Your GP examined you. That is the heart of the word.

In older texts you will meet the same thing as medically unexplained symptoms. Internationally it is called persistent physical symptoms, an umbrella term for distressing physical symptoms lasting several months or more, whatever the cause (PMID 38879263).

SOLK or ALK: why the term is changing

SOLK is on its way out. Since 2021 the Dutch network NALK, working with patients, uses ALK instead: Aanhoudende Lichamelijke Klachten, or persistent physical symptoms. The reason is that SOLK quietly took on a life of its own as a diagnosis, which it never was. ALK measures something else.

Where SOLK turns on whether your symptoms are explained, ALK turns on how long they last and what they do to you. A small change of words, a big change of tone.

Those bottom two rows are the real gain. With ALK nobody has to prove first that there is no disease before the symptoms are allowed to count.

That mostly helps people for whom both are true. You can have a treated thyroid condition and still keep chronic symptoms that it does not explain. Under SOLK, that fell between two stools.

What investigation usually precedes a SOLK diagnosis?

Before the label lands, your GP usually looks first at conditions that easily pass for something else. Think of your thyroid, anaemia and iron, inflammation markers, coeliac disease, diabetes and vitamin D or B12. What gets requested depends on your story, your physical examination and your age.

This is not a fixed list and not a box-ticking exercise. Two women, both tired, both with a TSH of 3.1 mIU/l. For one, that fits the rest of her story and the search stops there.

The other has weight loss and night sweats alongside it. The same number then counts differently, and more investigation usually follows.

That is not arbitrary. A value takes its meaning from what sits around it, and that is exactly what your GP weighs.

This table is here to help you read your own file, not to redo your GP's work. If a value is already in there, that question has been answered.

If you want to follow one thread further: thyroid symptoms in women, what a low ferritin means, what CRP and ESR mean, or coeliac disease: symptoms, testing and gluten-free living. If fatigue is the main thread, the broader overview is in always tired: which blood values to test.

One thing gets misread often. A normal result does not prove nothing is there. It means this particular explanation is not the one, and the search moves on.

Why do women get the SOLK label more often?

Women get this label more often, and that sits in how the system measures. Symptoms like pain and fatigue are subjective and hard to capture in a number. Some of the conditions that mainly affect women also lack a good test, and have been researched less for decades than the rest.

Dutch figures make this visible. Across 34,268 episodes of care in the Family Medicine Network, women received fewer physical examinations, less imaging and fewer specialist referrals than men, but more laboratory diagnostics (PMID 34385033).

For the same symptom, women also received a disease diagnosis slightly less often. In that same analysis, the difference ran through the number of investigations performed (PMID 34385033).

Read that figure carefully. This is a pattern across tens of thousands of episodes, not a verdict on any one consulting room. Differences like these exist only in the aggregate, and nobody feels them in the moment.

In the Lifelines study of 150,494 Dutch adults, female sex was associated with a persistently higher symptom level (OR 1.74) (PMID 33168107). Notably, that did not hold for femininity as a role pattern, which looked protective instead. Sex and gender are not the same thing, here either.

The sum of it is structural. Subjective symptoms are harder to pin down, some women's conditions simply have no good test yet, and the evidence base grew lopsided. Your GP can do little about that inside ten minutes.

How that lopsidedness came about is covered in more depth in why women's symptoms are missed more often.

Does SOLK mean it is all in your head?

No. SOLK says nothing about where your symptoms come from, only that no condition has yet been found that explains them well enough. Body and mind influence each other, and that is biology, not a brush-off. Stress can amplify pain without that pain being imagined.

The 2024 Lancet review lists, alongside psychosocial factors, persistent inflammation, immune and metabolic dysregulation, epigenetics and the microbiome (PMID 38879263). Biological and psychological, at the same time.

That is not an easy way out. It is the recognition that persistent symptoms rarely have a single cause.

Thuisarts puts it plainly: "Lichaam en geest beïnvloeden elkaar." Body and mind influence each other. Someone in pain becomes tense. Someone tense feels pain more sharply. That is a circle, not an accusation.

I think we read that circle as a reproach far too often. Attention to stress or low mood alongside your symptoms takes nothing away from your symptoms. The same Lancet authors name reducing stigma explicitly as a goal of better explanation (PMID 38879263).

What can you do after a SOLK diagnosis?

The most useful move is usually not to contest the conclusion, but to sharpen the conversation. List what has already been investigated and when. Describe your symptoms as patterns across weeks, not as separate days. If something changes or something new appears, that is a reason to go back.

A SOLK diagnosis is not a mistake for you to correct. So this article is not a checklist for auditing your GP, and that is deliberate.

What does help is preparation. How to go about it is in preparing for your GP appointment. If you genuinely doubt the path taken, the route of a second opinion exists.

If pain and stiffness through your whole body are the main thing for you, a more specific picture may fit better than the umbrella label. What gets looked at then is in fibromyalgia symptoms in women.

If your last blood test was a while ago, an extended health checkup can give you a current set of values to bring to your appointment. Such a panel does not diagnose anything, and it neither confirms nor refutes SOLK. It gives your GP some recent numbers to work with.

If you notice something new, such as weight loss, fever, or a symptom that changes character, book an appointment. That is not doubting the diagnosis. That is new information.

References

1. Haller H, Cramer H, Lauche R, Dobos G. Somatoform disorders and medically unexplained symptoms in primary care. Dtsch Arztebl Int. 2015;112(16):279-287. PMID 25939319.
2. Ballering AV, Muijres D, Uijen AA, Rosmalen JGM, Olde Hartman TC. Sex differences in the trajectories to diagnosis of patients presenting with common somatic symptoms in primary care: an observational cohort study. J Psychosom Res. 2021;149:110589. PMID 34385033.
3. Ballering AV, Wardenaar KJ, Olde Hartman TC, Rosmalen JGM. Female sex and femininity independently associate with common somatic symptom trajectories. Psychol Med. 2022;52(11):2144-2154. PMID 33168107.
4. Löwe B, Toussaint A, Rosmalen JGM, et al. Persistent physical symptoms: definition, genesis, and management. Lancet. 2024;403(10444):2649-2662. PMID 38879263.
5. Olde Hartman TC, Woutersen-Koch H, Van der Horst HE. Medically unexplained symptoms: evidence, guidelines, and beyond. Br J Gen Pract. 2013;63(617):625-626. PMID 24351464.
6. NHG-Standaard Somatisch Onvoldoende verklaarde Lichamelijke Klachten (SOLK). Dutch College of General Practitioners. Available via richtlijnen.nhg.org.
7. Thuisarts. Onverklaarde lichamelijke klachten. 2024. Available via thuisarts.nl.

Every blood test result at Lunara includes a professional assessment by a BIG-registered doctor. For treatment decisions, discuss your results with your GP.