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Many diseases start long before your body gives you any warning. You may feel perfectly healthy, exercise as usual and go to work every day – while your blood values are slowly changing in the background. With the right blood tests interpreted in the right context, they can provide important clues about the risk of diabetes, cardiovascular disease, kidney damage, liver disease and other conditions that are often silent at first.
5 blood tests that can reveal disease before you have symptoms
HbA1c – the blood test that can detect pre-diabetes
If you ask which blood test most often finds a disease at an early stage, HbA1c is high on the list. The test shows how much sugar has bound to the red blood cells over the past two to three months. It therefore gives a picture of your average blood sugar over time, not just a momentary value.
This is particularly valuable because type 2-diabetes often develops slowly. Many people have had elevated blood sugar levels for a long time without experiencing classic symptoms such as thirst, fatigue or increased urine output.
HbA1c can also indicate the early stage of prediabetes. There, the value is higher than normal but not yet at the level of diabetes. There is often a window in which lifestyle changes, weight loss, better sleep and more physical activity can reduce the risk of developing manifest diabetes.
An elevated HbA1c value can be detected in people who feel completely healthy and carry out a regular hälsokontroll. In this case, an elevated HbA1c value can indicate that the metabolism is already affected.
Blood fats – when cholesterol values show risk long before the first heart attack
High blood fats are rarely felt. You do not experience any particular pain from an elevated LDL-cholesterol, and the body rarely sends clear warning signals. Nevertheless, blood lipid disorders over many years can contribute to arteriosclerosis, i.e. fat and inflammation build up in the blood vessel wall and increase the risk of heart attack and stroke.
A health check for specific lipids, often also called a lipid panel, usually includes total cholesterol, LDL, HDL and triglycerides. In some people, ApoB or lipoprotein(a), Lp(a), can also provide a more accurate risk picture. This is especially true if you have diabetes, metabolic syndrome, high triglycerides or a strong heredity for early cardiovascular disease.
This blood test can not only detect “generally high cholesterol”, it can also raise suspicion of hereditary disorders, such as familial hypercholesterolemia. If a person has such a condition, they can have very high LDL levels already at a young age and still feel completely fine, even though the risk of early cardiovascular disease is greatly increased if the condition is not detected.
Creatine and eGFR – small changes that can reveal early kidney disease
Kidney disease is often silent for a long time. Many people do not notice anything until kidney function is already clearly impaired. That is why blood tests that measure creatinine and estimated kidney function, eGFR, are central to preventive health checks.
Creatine is a waste product from muscle metabolism. When the kidneys filter less well, creatinine rises in the blood, and the laboratory can then calculate eGFR, which estimates how well the kidneys filter. A single abnormal test does not always mean chronic kidney disease, but it can be the first signal that something needs to be followed up.
Early kidney damage is particularly common in people with diabetes, high blood pressure, cardiovascular disease or advanced age. In these groups, kidney tests are used regularly because early detection can affect both treatment and prognosis.
Creatinine is a good blood test, but it alone cannot provide the whole picture. If you really want to detect early kidney damage, a urine test for albumin is often also needed. A blood test can therefore provide the first clue, while the combination of blood and urine tests provides a more reliable assessment.
Liver tests - elevated values can be the first sign of fatty liver or hepatitis
The liver can be affected for a long time without giving clear symptoms. Many people with fatty liver, viral hepatitis or other chronic liver disease feel fully capable of working and do not seek care until late in the process. Therefore, liver tests such as ALT and AST can play an important role in early detection.
ALT and AST are enzymes that leak into the blood when liver cells are irritated or damaged. Elevated values do not automatically mean serious disease, but they signal that the liver may need to be investigated. According to liver specialist guidelines, chronic or recurrent elevated ALT or AST over about six to twelve months can indicate ongoing liver damage, even when the person does not have symptoms.
A common example is metabolically associated fatty liver, previously often called NAFLD. It is strongly linked to obesity, insulin resistance, type 2 diabetes and blood lipid disorders and is often asymptomatic. At the same time, elevated ALT can also lead to further testing for other causes, such as alcohol-related liver disease, drug effects or hepatit C which is also a good example of a disease that can be detected via blood tests before symptoms occur.
TSH – when blood tests can find a slow metabolism at an early stage
The thyroid gland controls large parts of the body's metabolism. When it works too slowly, hypothyroidism, you can get fatigue, chills, constipation, dry skin and weight gain. The problem is that early symptoms are often so diffuse that they are easily explained by stress, lack of sleep or high workload.
The blood test that is most often used first is TSH, a hormone from the pituitary gland that controls the thyroid. In primary hypothyroidism, TSH rises when the body tries to pressure the thyroid gland to produce more hormone. According to endocrinology guidelines, TSH is the best first screening test for primary thyroid disorders in most outpatient settings.
TSH is most meaningful when there are symptoms, heredity, autoimmune disease, pregnancy, medications that affect the thyroid or other risk factors. In a health check or a health test package regarding blood tests for thyroid function, TSH can be very relevant for someone with increasing fatigue and a family history, but less accurate as a general screening for everyone.
When blood tests actually do the most good
There is a persistent idea that more testing is always better. It is not that simple. A blood test is most useful when it has a clear purpose: to detect a treatable risk, explain symptoms or follow a condition over time.
It also means that results must be interpreted in context. A slightly elevated liver value in a person who has exercised hard, drank alcohol the night before or recently started taking medication means something different than the same value in a person with diabetes and abdominal obesity. Similarly, a normal HbA1c can be reassuring, but does not rule out all forms of impaired glucose metabolism if the risk profile is high.
For those considering a health check-up, the practical question is often simple: which diseases do you want to detect early, and which tests respond best to that? It is often wise to combine blood sugar, blood lipids, kidney values and liver tests, and if necessary add thyroid tests or iron status, for example. This way, the testing becomes more accurate than if you order individual tests without a plan.
A test result is not just a message about illness or health. It can also be a starting point for change. When test results make the risk concrete, it is often easier to address sleep, exercise, drinking habits, weight, blood pressure or follow-up in healthcare before the body has time to protest.
Do you want to know what your values look like? Order a hälsokontroll from Testmottagningen.se and get a clear basis for the next step.
