Blood tests worth asking for
If your weight will not move, a small number of blood tests can tell you whether something measurable is involved. This is the list, what each test shows and why it matters. Print it, take it to your GP, or ask us to order it. Not every test suits every person, and your clinician decides what is appropriate for you.
Justin Black, Nurse Practitioner · Published 10 September 2026
Medically reviewed by Justin Black, Nurse Practitioner · 10 September 2026
Written from Australian and international clinical guidance and peer-reviewed research, and reviewed by a registered nurse practitioner before publication. Our clinicians are registered with AHPRA and searchable on the public register.
This article is general information, not medical advice, and it is not a diagnosis or a treatment recommendation. Talk to your own clinician about your situation.
The list
Not a prescription and not a checklist to insist on. It is what is commonly relevant, so you can have a specific conversation rather than a vague one.
| Test | What it shows | Why it matters |
|---|---|---|
| TSH, with free T4 if abnormal | Thyroid function | An underactive thyroid slows resting energy use and causes fluid retention. Common, cheap to check, and treatable. |
| HbA1c | Average blood glucose over about three months | Picks up insulin resistance and early glucose problems years before symptoms. Does not require fasting. |
| Fasting glucose and fasting insulin | How hard the pancreas is working | Insulin can be high for a long time while glucose still looks normal. Glucose alone can miss it. |
| Lipid profile | Cholesterol and triglycerides | Triglycerides in particular track with insulin resistance and central fat. |
| Liver function, including ALT | Liver stress | Fatty liver is common with central weight and usually silent until it is advanced. |
| Full blood count | Anaemia and general picture | Fatigue blamed on weight is sometimes anaemia, and it is trivial to exclude. |
| Iron studies, including ferritin | Iron stores | Low iron causes fatigue and poor exercise tolerance, which changes what you can do. |
| Vitamin B12 and folate | Deficiency affecting energy | Worth checking if fatigue is a main feature or if you follow a restricted diet. |
| Vitamin D | Deficiency | Common in Australia despite the climate, particularly in winter and with indoor work. |
| Kidney function and electrolytes | Baseline | Context for everything else, and relevant before some treatments. |
| Testosterone (men) | Hormonal contribution | Low testosterone and central weight influence each other in both directions. |
| LH, FSH and oestradiol (women) | Where you are in the menopause transition | Interpreted alongside your cycle and symptoms rather than alone. |
| Androgens and SHBG (women) | PCOS assessment | Where PCOS is suspected, alongside cycle history and ultrasound if indicated. |
| Coeliac screen | Coeliac disease | Worth considering where there are bowel symptoms, iron deficiency or a family history. |
How to use it
Take it with you and say what you have noticed and when it started. A clinician deciding which of these apply needs your history more than the list. Ask which ones are relevant to you and which are not, because the answer to "not that one, and here is why" is as useful as the test.
Some tests need fasting and some do not. The request form will say, and the collection centre will tell you.
When results come back normal
That is a real result, not a dead end. It rules out the measurable causes and moves the conversation to sleep, medicines, stress, eating patterns and the physiology of weight that has been lost and regained before. Normal results are frequently the point at which a useful plan finally becomes possible.
What this page is not
General information, not medical advice and not a diagnosis. Which tests are appropriate, and what any result means for you, is a clinical decision that needs your history alongside the numbers.
What you can do next
If you want the relevant tests, we can order them, or you can take the list to your GP. Either is fine, and you do not need to book with us to use anything on this site.
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