I'm in my early 30s. Should I start watching my blood fats?

Your early 30s are a good time to start knowing your blood fat numbers. MedlinePlus, from the US National Library of Medicine, advises adults aged 20 to 65 to have their blood lipids tested every 5 years, while England's NHS invites people aged 40 to 74 to a health check that includes a cholesterol test every 5 years. So timing differs by country, and it also depends on your family history. Once you have results, keep them to compare from year to year, have a doctor read them, and start paying attention to everyday habits now.

What blood fat values appear on a health check report?

The blood fat section of a health check is sometimes called a lipid profile. MedlinePlus describes it as a blood test that measures the amount of cholesterol and triglycerides in your blood.

The four values you usually see

LDL marked "calculated"

MedlinePlus explains that if your LDL says "calculated", it is an estimate based on your total cholesterol, HDL and triglycerides. Some labs measure LDL directly from the blood sample instead.

VLDL, which some reports leave out

MedlinePlus notes there is another type called VLDL, which mainly carries triglycerides. It is not usually included in routine tests because it is difficult to measure, and a lab may estimate it from your triglycerides. If your report does not show it, that is normal.

Do I need to fast before a blood fat test?

You may. It depends on the clinic and the tests.

The usual fasting time

MedlinePlus says you may need to fast, not eating or drinking, for 9 to 12 hours before the blood test, and that your provider will tell you whether you need to and about any other special instructions. If you do need to fast, a morning appointment means most of the fasting time falls while you sleep.

Follow the clinic's instructions

Clinics can give different advice. When you book, ask how many hours to fast, whether plain water is allowed and what to do about regular medicines. If you ate something before the test by mistake, tell the staff honestly.

At what age should I start testing, and how often?

There is no single worldwide rule. Countries have different guidance, and how often a person needs testing depends on their own risk.

Guidance from two countries

Under the US guidance, someone in their early 30s falls in the every-5-years group. In England, NHS invitations start at 40. In Thailand, annual health check packages from workplaces and hospitals include different items, so check whether yours has a blood fat section, and if not, ask the clinic whether to add one.

When you may need tests more often

MedlinePlus says how often you are tested depends on your age, risk factors and family history, and that you may need tests more often if, for example:

• close family has had heart problems
• you smoke
• you are not physically active
• your diet is high in saturated fat

If any of these apply, tell the doctor and ask how far apart your tests should be.

How do I read the numbers on my results?

Results are usually given in milligrams per decilitre (mg/dL), with the lab's reference range printed next to them.

The levels MedlinePlus uses in the US

This table shows the levels MedlinePlus uses for adults aged 20 and over. It is a US example, not a Thai standard.

Have a doctor read them with your history

MedlinePlus says a healthy level for you may depend on your age, family history, lifestyle and other risk factors, so a single number does not tell the whole story. Ask the doctor what your values mean, which ones to keep an eye on and when to test again.

Keep your results to compare

Your early 30s are a good point to start keeping a personal baseline. Photograph or file every report and take them to your next appointment, so the doctor can see how your values change as your age and lifestyle change.

What everyday habits are worth paying attention to in my 30s?

The 30s are often busy years: long hours sitting, eating out and frequent work dinners. The guidance below is general advice for adults from health agencies.

Moving your body

WHO advises adults to do 150 to 300 minutes of moderate-intensity activity, such as brisk walking, or 75 to 150 minutes of vigorous activity a week, plus muscle-strengthening on 2 or more days, and to limit time spent sitting. If you are not active yet, start with short walks and build up.

The kind of fat and how food is cooked

WHO says the quality of dietary fat matters. Unsaturated fat, found in fish, avocado, nuts and sunflower, soybean, canola and olive oils, is preferable to saturated fat, found in fatty meat, butter, palm and coconut oil, cream, cheese and lard, and to trans fat. WHO advises getting no more than 10% of daily energy from saturated fat, steaming or boiling instead of frying, choosing lean meat and limiting fried and baked foods and pre-packaged snacks.

Thailand's eating guidelines

Thailand's food-based dietary guidelines from the Department of Health include eating food from all 5 food groups, eating rice as the main staple, eating fish, eggs, lean meat and dried beans, eating vegetables and fruit regularly, cutting down on sweet, fatty and salty food, and drinking enough clean water.

Smoking and alcohol

MedlinePlus says smoking lowers HDL cholesterol, especially in women, and raises LDL. The Department of Health's guidelines include avoiding or cutting down on alcohol. If you smoke or drink often, mention it to the doctor at your health check.

What should I prepare before talking to the doctor?

An early blood fat test in your 30s is most useful when the doctor has the full picture.

What to bring

• previous results, if you have them
• your family history, such as whether close family has had heart or blood vessel problems
• how much you smoke, drink and move in a typical week
• any medicines you take regularly

What to ask

• what each of your values means and which ones to keep an eye on
• when to test again
• how to prepare for the next test

If a result is flagged, follow the advice of a doctor who knows your history rather than deciding from one number on your own.