Knowledge base
A low ferritin means your iron stores are running low, and then you want one thing: to get them back up. Why the cause matters more than the list of iron-rich foods, what really determines iron absorption and when tablets are and are not sensible.
Values: Ferritin · Iron · Transferrin
From around the age of forty-five all sorts of things change: your cycle becomes unpredictable, you sleep worse and you sometimes barely recognise your own mood. The question that follows is a logical one: can I have this measured? What hormone testing during the menopause does offer, and where it falls short.
Values: FSH · Oestradiol · LH · Progesterone
Seeing that your liver values are raised is unsettling. Yet a mild rise is often harmless and temporary, and a single measurement says little without context. What ALT and AST actually measure, which causes are most common and when looking further is genuinely needed.
Values: Liver enzymes (ALT + AST) · Gamma-GT · Alkaline phosphatase · Bilirubin
You train consistently, yet your performance stalls or your legs stay heavy. So you start looking. Blood testing can provide part of the answer, provided you measure the right values at the right moment. Which tests matter for athletes, and which results easily put you on the wrong track.
Values: Ferritin · Iron · Haemoglobin · Creatinine + eGFR
Weeks of taking on too much, sleeping badly and a body that no longer cooperates. The thought that your stress hormone is out of order is an obvious one. You can have cortisol measured, but the result answers a different question than most people expect. Here is what you can and cannot take from it.
Values: Cortisol · TSH · Free T4 · Ferritin
Folate, also known as vitamin B11 or folic acid in its supplement form, comes up in two very different conversations: around a wish to conceive and around unexplained fatigue. In both cases the question is whether testing helps. The answer differs per situation, and that difference is what this article is about.
Values: Folic Acid · Vitamin B12 · Haemoglobin · Ferritin
A plant-based diet is perfectly sustainable for most people, provided you know which nutrients need attention. A deficiency develops quietly and only causes complaints late on. Which blood values matter for vegetarians and vegans, and when measuring is worthwhile.
Values: Vitamin B12 · Ferritin · Vitamin D · Folic Acid
A vitamin B12 deficiency develops slowly and causes complaints you easily attribute to something else: tiredness, thinking less sharply, tingling in the hands or feet. What the causes are and why only a blood test gives certainty.
Values: Vitamin B12 · Folic Acid · Haemoglobin · Ferritin
Tired for no clear reason, more hair loss than you are used to, or restless legs at night. With those complaints, iron is often the first suspect. Ferritin is the marker that moves first, but it is also the marker most often misread.
Values: Ferritin · Iron · Transferrin · Haemoglobin
A cholesterol profile consists of four values, and they do not all tell the same story. What total cholesterol, LDL, HDL and triglycerides actually mean, why doctors focus mainly on LDL and when a measurement is useful.
Values: LDL cholesterol · HDL cholesterol · Total cholesterol · Triglycerides
A fasting glucose tells you how your blood sugar stood at that one moment. HbA1c looks much further back, at the average of the past two to three months. What that value measures and who benefits from having it done.
Values: HbA1c · Glucose · Insulin · Haemoglobin
Everyone is tired now and then. If the fatigue lasts for weeks even though you sleep enough, it makes sense to think about your blood. Which blood values tell you the most with persistent tiredness, and when a blood test is precisely not the answer.
Values: Ferritin · TSH · Free T4 · Vitamin B12
More hair in your brush or on your pillow than you are used to. Hair loss often has an innocent or hereditary explanation, but sometimes a deficiency or a hormonal shift plays a part that can be seen in blood. Which blood values can play a role, and what a blood test does and does not tell you.
Values: Ferritin · Iron · TSH · Free T4
Dizziness has many faces: the room spinning, feeling light-headed when standing up, or being unsteady on your feet. The cause often lies in the balance organ or blood pressure regulation, and sometimes in the blood. When a blood test is worthwhile and which values tell you the most.
Values: Haemoglobin · Glucose · Sodium · Potassium
A bottle of water always within reach, and waking up at night to go to the toilet. It is a combination that is easily dismissed, while it can be one of the first signals of a raised blood sugar. What glucose and HbA1c tell you, and when testing is worthwhile.
Values: Glucose · HbA1c
TSH is almost always the first value measured when the thyroid comes to mind. If your result is flagged as abnormal, the first question is not what you have, but what else is needed to know that. What TSH actually measures, and why the result works the opposite way to what you might expect.
Values: TSH · Free T4 · Free T3 · Anti-TPO
Having your iron tested sounds simple, but there are three ways of looking at it and they do not give the same answer. What serum iron, ferritin and transferrin each measure, why inflammation can distort the picture, and when each test genuinely helps you further.
Values: Ferritin · Iron · Transferrin · CRP
A cholesterol profile gives a good first impression, but it does not tell you everything. ApoB shows how many particles are actually travelling through your blood vessels. Lp(a) reveals a largely inherited risk that lifestyle barely changes. What both values add and who they are useful for.
Values: LDL cholesterol · Total cholesterol · HDL cholesterol · Triglycerides
Your kidneys do their work without you noticing, and that is exactly the problem: if they start working less well, you often feel it only late. Creatinine and eGFR are the values used as standard to assess kidney function. What they measure, where they fall short and when testing is useful.
Values: Creatinine + eGFR · Cystatin C · Urea · Uric acid
CRP is one of the most frequently requested blood values and at the same time one of the most misunderstood. It shows that inflammation is present in your body, but not where and not why. What CRP does and does not tell you, what hsCRP adds and when measuring is worthwhile.
Values: CRP · ESR (sedimentation rate) · Haemoglobin · Ferritin
Muscle cramps that wake you at night, an eyelid that keeps twitching, tiredness that will not pass. A magnesium deficiency is rarely the first suspect, yet this mineral is involved in hundreds of processes in the body. Which complaints fit, what the causes are and why a blood test only tells part of the story.
Values: Magnesium · Calcium · Potassium · Ferritin
What a blood test costs depends mainly on two things: which route you take and how many and which markers are measured. In this article we set both routes out honestly, with real prices, so you know where you stand in advance.
Values: Potassium · Sodium · Liver enzymes (ALT + AST) · Vitamin B12
An irregular cycle, mood swings, hot flushes or persistent fatigue: many complaints are quickly blamed on hormones. Rightly or not? A blood test can give part of the answer, provided you measure the right hormones at the right moment. This is what you can measure, and what you can and cannot expect from it.
Values: Oestradiol · Progesterone · FSH · LH
Creatinine has been the standard for estimating kidney function for years. But in people with high or low muscle mass, it sometimes gives a distorted picture. Cystatin C largely solves that problem. What it measures and when it is useful.
Values: Cystatin C · Creatinine + eGFR · Urea · Uric acid
A PSA test measures a protein produced by the prostate. The result can provide a clue, but proves nothing on its own: an elevated value often has an innocent explanation, and testing without symptoms is a choice with both advantages and disadvantages. Here you can read what the test does and does not tell you, so you can make an informed decision.
Values: PSA
A vitamin D deficiency is common in the Netherlands, especially towards the end of winter. Yet the complaints that can fit a deficiency, such as fatigue and muscle complaints, are far from specific. When does testing make sense, who is advised to supplement regardless, and what do you do with the result?
Values: Vitamin D · Calcium · Magnesium · Vitamin B12
Less energy, a lower sex drive or a gloomy undertone: testosterone is quickly blamed, especially by men. Yet these complaints can rarely be pinned on a single hormone. What a testosterone test does and does not measure, why the time of the blood draw matters and why SHBG belongs alongside it.
Values: Testosterone · Free testosterone · SHBG · LH
Persistent fatigue can have dozens of causes, and the thyroid is often the first one mentioned. Rightly so or not? A blood test makes this lead relatively easy to check. What TSH and free T4 do and do not tell you.
Values: TSH · Free T4 · Anti-TPO · Ferritin
GLP-1 medications such as semaglutide, known to many as Ozempic, receive a great deal of attention in medical weight loss. They are prescription medicines that belong exclusively with a treating doctor. What these medications actually do, why blood testing before and during a weight loss programme can be worthwhile, and what a result does and does not tell you.
Values: HbA1c · Glucose · Insulin · Liver enzymes (ALT + AST)
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