Feeling well at 25 or 35 is the norm. That is exactly why so few people in their 20s and 30s have ever seen their own cholesterol, blood sugar or iron results. Nothing hurts, so nothing gets checked. Yet this is the age when a first set of numbers is most useful: it becomes the baseline you compare everything with later. This article looks at which blood tests usually make sense in your 20s and 30s, and why.
Why a check-up in your 20s and 30s
Many of the things that shape heart health later in life start early and give no signs. A review on heart and circulation risk in adults aged 20 to 39 lists the features that matter most at this age: smoking, raised blood pressure, a family history of early heart disease, very high cholesterol that runs in families and diabetes (Stone et al., 2022). Most of these can only be seen with a measurement.
Inherited high cholesterol is more common than people think: a meta-analysis estimated it affects about 1 in 250 people (Akioyamen et al., 2017). It usually gives no symptoms, so a blood test is the only way to know your level.
The first numbers worth knowing
Cholesterol
A cholesterol profile measures total cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL) and triglycerides. One result will not tell you much about your future on its own, but it shows where you start, and whether it is worth talking to your GP sooner, especially if heart problems run in your family.
Blood sugar
Glycated haemoglobin (HbA1c) reflects your average blood sugar over the past 2 to 3 months. Type 2 diabetes can start early and often gives no symptoms at first. A first HbA1c result is a simple reference point.
Vitamin D
Between October and early March, the NHS says we do not make enough vitamin D from sunlight in the UK, and it advises everyone to consider a daily 10 microgram supplement in autumn and winter. A test in late winter shows where you are at the lowest point of the year.
Iron
Iron deficiency is one of the most common nutritional problems in the world, and it particularly affects women before the menopause. It can affect how you feel even without anaemia (Pasricha et al., 2021).
Women in their 20s and 30s
Heavy periods and pregnancy are very common causes of iron deficiency anaemia, according to the NHS. Heavy menstrual bleeding is so common that it is often treated as normal, by women themselves and by health services, and the low iron that follows is easy to miss (Munro et al., 2023). If your periods are heavy or you feel tired all the time, an iron profile with ferritin is a sensible place to start, and the heavy periods themselves are worth raising with your GP.
The thyroid comes into view in your 30s. Hashimoto's disease, the main cause of an underactive thyroid in the UK, is most common in women and usually starts between 30 and 50 (NHS). Its signs, such as tiredness and weight gain, look like many other things, which is why thyroid stimulating hormone (TSH) is often part of a check-up at this stage.
If you are planning a pregnancy, see women's health blood tests and the planning a baby page, which cover folic acid, iron and immunity.
Men in their 20s and 30s
For most men, cholesterol and blood sugar are the first numbers that matter. Testosterone falls slowly with age, about 1% a year from around 30 to 40, which the NHS says is unlikely to cause problems in itself. It is worth measuring when you have symptoms, such as a low sex drive, and the sample is best taken in the morning. Read more in men's health blood tests.
Diet, training and lifestyle
- Vegan or strict vegetarian diet: the NHS lists a vegan diet without B12 supplements or fortified foods as a risk for low vitamin B12.
- Hard training: iron, vitamin D and recovery markers matter more. See blood tests for athletes.
- Regular drinking: liver enzymes such as alanine aminotransferase (ALT) and gamma-glutamyl transferase (GGT) are part of most general profiles.
The 18 to 29, women 30 to 39 and men 30 to 39 pages list the usual tests for each group, with the research behind them.
