"I've had bloods done": why this phrase tells you almost nothing
One of the most common phrases I hear from new patients is some version of "I've had my bloods done." It usually comes with a reassuring confidence, as though a blood test is a blood test in the same way a haircut is a haircut.
It isn't.
What gets ordered depends entirely on who ordered it and why. A specialist sees you for one reason and orders tests relevant to that reason. A cardiologist checking your heart might order a full lipid panel. An orthopaedic surgeon preparing you for a knee replacement might only order a blood group and cross-match. An emergency department doctor treating a kidney stone orders a different set again. None of them are doing a full health workup. They are answering a specific clinical question.
Take diabetes screening as one example. HbA1c (a three-month average of blood sugar levels, which screens for prediabetes and type 2 diabetes) and fasting glucose (a single snapshot taken after not eating overnight) both check for the same conditions. Different GPs prefer different tests: some use one, some the other, some order both. If you have had one done but not the other, you may not know which it was, or what a normal result on that particular test actually rules out.
What follows is a guide to the blood tests worth knowing about and asking after before you turn 50.
Interactive guide
Your GP will determine which tests are clinically appropriate based on your history and risk factors. These are the ones worth knowing about and raising.
This guide is for general information only. Your GP will determine which tests are clinically appropriate based on your individual history, symptoms, and risk factors. Not all tests and services attract a Medicare rebate and there may be costs, discuss with your doctor.
What a thorough blood test workup in your 30s and 40s actually covers
The RACGP guidelines (the national standard for preventive care in general practice) recommend cardiovascular risk assessment, including a full lipid panel, routinely from age 45. Diabetes screening is recommended from 40 for people with risk factors. For Aboriginal and Torres Strait Islander peoples, both start significantly earlier.
In practice, these tests are often ordered well before those thresholds. Guidelines represent population-level starting points, not clinical ceilings. A 36-year-old with a family history of early heart disease, central weight gain, and elevated blood pressure does not benefit from waiting nine more years to know their cholesterol.
The 30s tier is risk-factor driven. If you are in your 30s and have a family history of cardiovascular disease, diabetes, or kidney disease, that changes what warrants checking and when. By your 40s, a proper workup is a routine conversation regardless of symptoms.
A thorough GP workup in your 30s and 40s may cover the following. Which tests are ordered will depend on your history, your risk factors, and your clinical picture. These are the ones worth knowing about and asking after.
Checks your red blood cells (which carry oxygen to your tissues), white blood cells (which form part of your immune response), and platelets (which assist with clotting). A useful baseline, and one that can flag anaemia, infection, and a range of other conditions. An FBC alone does not cover cholesterol, blood sugar, liver function, kidney function, or most of what follows. If you have had an FBC recently, it does not mean the rest of your workup is current.
Total cholesterol, LDL (low-density lipoprotein, often called "bad cholesterol" because it deposits in artery walls over time), HDL (high-density lipoprotein, the "good" fraction that helps clear the arteries), and triglycerides (a type of fat in the blood that tends to rise with excess sugar, alcohol, and processed carbohydrates). The full panel tells you far more than total cholesterol alone. Total cholesterol on its own misses important information.
Both screen for prediabetes and type 2 diabetes before symptoms appear. HbA1c reflects average blood sugar over the past three months. Fasting glucose is a snapshot. Your GP will choose based on your clinical picture. If you have been told your blood sugar was normal but do not know which test was used, it is worth asking.
A set of enzymes and proteins that reflect liver health. Increasingly relevant given how common fatty liver disease has become. It is frequently silent in its early stages and can progress significantly before a person feels any different.
eGFR, or estimated glomerular filtration rate, is a calculated measure of how well your kidneys are filtering waste from the blood. Kidney disease is almost always asymptomatic in its early stages. A baseline in your 40s matters for tracking function over time.
The primary screening test for thyroid dysfunction. An underactive or overactive thyroid produces symptoms that are broad and easy to attribute to other causes: fatigue, weight changes, mood shifts, temperature sensitivity. Used when the clinical picture suggests thyroid dysfunction.
Measures your iron stores, not the iron currently circulating in your blood. The distinction matters. More on this below.
One worth asking about given how common low levels are, even in a sun-exposed city like Adelaide.
A note on fasting: Several of these tests require fasting, meaning no food or drink (water is fine) for 8-10 hours beforehand. This applies particularly to the lipid panel and fasting glucose. Book a morning appointment and have the blood drawn before breakfast if you can. Your GP will tell you which tests need fasting when they order them.
The number most people in their 30s and 40s have never been told
When I was working on the stroke rehabilitation team during my hospital training, I met patients in their 40s who had suffered strokes. Several of them had never had a full lipid panel done. Not because they had been failed by anyone in particular. Simply because the conversation had not happened.
Lipid abnormalities are silent. Raised LDL, raised triglycerides, low HDL. None of these produce symptoms. You feel completely normal while atherosclerosis (the gradual narrowing of arteries caused by fatty deposits building up in artery walls) progresses quietly over years.
Part of what I see in my practice reflects a food environment that has changed dramatically within a single generation. Previously, most diets were built around whole foods: protein, vegetables, fruit, animals raised and cooked simply. The transition to a diet where ultra-processed foods form a large proportion of daily intake has been rapid and significant. Breakfast cereals engineered to taste like confectionery. Snack foods designed to be difficult to stop eating. Flavoured milks, fruit juices, processed lunchbox foods. These things accumulate. Their effect on the lipid profile is real and measurable. A substantial proportion of my patients in their 30s and 40s have raised LDL, raised triglycerides, or low HDL, often without knowing.
The ones who know can do something about it.
For patients with a strong family history of early cardiovascular disease, a GP may also order lipoprotein(a), abbreviated Lp(a). Lipoprotein(a) is a type of lipoprotein particle, similar to LDL but with an additional protein attached that makes it more prone to causing arterial damage. It is largely determined by genetics and does not respond much to diet or lifestyle changes. The evidence on routine Lp(a) testing for everyone is still developing, but for patients with a family history of premature heart attacks or strokes, it is a once-in-a-lifetime measurement worth discussing. In some higher-risk patients, a GP may also check apolipoprotein B (ApoB): a measure of the total number of LDL particles in the blood that can reveal cardiovascular risk that a standard cholesterol result underestimates.
Ferritin and vitamin D: two tests your last blood test probably did not include
Ferritin is a protein that stores iron in your tissues. It measures your iron reserves, not the iron currently circulating in your blood. This distinction matters more than most people realise.
The reason ferritin matters is the gap between what a standard blood test shows and what is actually happening in your body. You can have a normal iron level and a low ferritin, meaning your stores are depleted even though your current blood level looks adequate. The symptoms, fatigue, difficulty concentrating, poor exercise tolerance, reduced recovery from physical activity, can be present for a long time before anything looks clearly abnormal on a standard FBC.
A common experience, particularly among women in their 30s and 40s, is persistent fatigue that does not resolve with rest. A previous blood test came back normal. But "normal" on a standard blood test often means the FBC looked fine, not that ferritin was checked. Women with heavy periods are a well-recognised risk group, but low ferritin also turns up in people eating what they believe is a varied diet and in those whose only symptom is tiredness they have put down to a busy life.
Vitamin D deficiency is genuinely common in Australia, including in a sun-exposed city like Adelaide. Vitamin D is primarily made by your skin in response to UV radiation, but indoor work, clothing, sunscreen use, and winter sun angle all limit how much you produce. A significant proportion of patients have vitamin D levels below the deficiency threshold (50 nmol/L), or below the 75 nmol/L level that some specialists consider optimal for bone health, muscle function, and immune response.
The response I hear most often when sharing a low vitamin D result: "But I live in Adelaide." Yes, and in Adelaide's winter, at our latitude, midday UV levels can be insufficient for adequate vitamin D synthesis for months at a time. Latitude alone does not guarantee adequate vitamin D, particularly for people who spend most of their daylight hours indoors.
Do I need a private blood panel?
Direct-to-consumer blood testing services have made it easier for Australians to order their own results without a GP referral. The motivation makes sense. You want to know your numbers. You want to feel in control of your health. You do not want to wait.
The limitation is not the accuracy of the tests. The limitation is what happens with the results.
A result outside the reference range does not arrive with a clinical history, a physical examination, knowledge of whether you fasted, whether you are dehydrated, whether a medication you take affects the result, or whether that particular reference range applies to someone of your age, sex, and background. In a panel of 40 or 50 results, several values will fall slightly outside range by chance alone. Statistically, that is expected. Clinically, each one requires a judgement call about whether it means something.
If you arrive at a GP appointment with a private panel, a good GP will work through it with you. But the most efficient path to genuinely useful results is one where the tests are chosen for you specifically, the fasting requirements are explained upfront, and the interpretation happens in the context of a thorough clinical assessment.
What to do if you have not had a proper workup
If you are in your 30s or 40s and you are not sure when you last had a comprehensive blood test, book an appointment and have that conversation with your GP.
Come with your family history if you know it. A parent, sibling, or grandparent who had a heart attack before 60, who has been treated for high cholesterol, or who has type 2 diabetes. These details change what gets ordered and how the results are read.
Come with your symptoms, even the ones you have dismissed as normal. Fatigue you have chalked up to poor sleep. Weight that has shifted over the past few years without an obvious cause. Energy that does not fully restore with rest. These have clinical patterns, and blood tests frequently illuminate them.
You do not need to arrive with a list of tests you want ordered. Bring your history. The clinical decisions follow from there.
For more on what to expect from a preventive health check, see our Preventive Health page. For information on blood sugar and diabetes risk, see What is prediabetes?
Common questions
