What Your GP Blood Tests Can and Cannot Tell You

Your GP's blood tests can support prevention as well as diagnosis. HbA1c, for example, can identify prediabetes before type 2 diabetes develops. The useful question is which tests could change your care. 1

Standard Panel Limitations

Start with the actual request or results, not the label “standard panel”. Check whether it included a full blood count, glucose or HbA1c, cholesterol, liver, kidney and thyroid tests.

A normal glucose result does not exclude insulin resistance. Equally, that limitation does not mean everyone needs fasting insulin or an expanded wellness panel. 2

Metabolic and Thyroid Markers Worth Discussing

HbA1c reflects average blood glucose over roughly three months and does not require fasting. It provides a longer view than a single glucose measurement, but does not show individual spikes or dips. 1

Iron-deficiency anaemia and conditions affecting red blood cells can distort HbA1c. If it conflicts with symptoms or other results, your GP may use another glucose test. 1

Fasting insulin: the pancreas can produce more insulin to keep glucose normal as insulin sensitivity falls. This explains why glucose alone does not describe the whole process. 2

However, insulin-resistance testing is not usually part of routine diabetes care. That mechanism alone does not establish fasting insulin as a better screening test. 2

For more detail, see insulin resistance and early markers.

Thyroid tests: TSH is generally the first test for suspected thyroid dysfunction in adults. A raised TSH can flag subclinical hypothyroidism rather than conceal it. 3

Free T4 is added when TSH is raised; free T4 and free T3 when it is low. Suspected pituitary disease needs a different approach. Thyroid antibodies help answer specific questions, not complete everyone's panel. 3

Nutrient Status: Ferritin and Vitamin D

Ferritin helps assess iron stores. It may be useful with heavy periods, unexplained fatigue or other reasons to suspect iron deficiency. 4

High ferritin does not automatically mean excess iron: inflammation and liver disease can also raise it. Interpret it with the clinical picture and other tests where needed. 4

Vitamin D matters for bone health, and NZ levels vary with season and sun exposure. However, seasonal variation alone does not justify testing everyone twice yearly. 5

Testing can help investigate suspected metabolic bone disease or significant deficiency. Routine testing before or after supplementation is usually unnecessary. 5

Inflammation and Cardiovascular Risk

High-sensitivity CRP, or hsCRP, is an inflammation marker used in cardiovascular risk assessment. The ACC's 2025 statement supports broader testing alongside cholesterol. 6

Recommendations differ. The USPSTF's 2018 assessment found insufficient evidence that adding hsCRP to standard assessment improves outcomes in asymptomatic adults. Ask what the result would change for you. 7

Homocysteine is influenced by B12, folate and B6 status and is associated with cardiovascular risk. However, lowering it generally has not reduced heart attacks or strokes. It is not a routine test for everyone. 8

How to Request Additional Tests

Bring a short list of symptoms, family history, medicines, supplements and previous results. Frame the conversation around a question to investigate, rather than a panel to obtain.

Ask:

What have we already checked?
Which additional test could change the next step?
Would an abnormal result need confirmation?
Is it funded, and who will explain the result?

Community laboratory funding is not governed by Pharmac's medicine funding criteria. Awanui's Wellington guidance identifies Health NZ funding and excludes some wellness testing. Check local rules and charges. 9

How Often Should You Test?

Agree on timing for each test. Follow-up depends on the condition, previous results and treatment, rather than a comprehensive panel every six to twelve months. 1 3

If fatigue persists or thyroid-type symptoms worsen, arrange a clinical review rather than waiting for a scheduled wellness panel. 3 4

Keep results with their dates and the agreed next step. Our guide to building a personal health dashboard can help you organise that record.

References

1.National Institute of Diabetes and Digestive and Kidney Diseases. The A1C Test & Diabetes. Source

2.American Diabetes Association. Understanding Insulin Resistance. Source

3.National Institute for Health and Care Excellence. Thyroid disease: assessment and management. NICE guideline NG145.[Full guideline hosted by NCBI Bookshelf.] Source

4.MedlinePlus. Ferritin Blood Test. Source

5.Ministry of Health and Cancer Society of New Zealand. Consensus Statement on Vitamin D and Sun Exposure in New Zealand. 2012.[Used for NZ context and selective-testing principles, not historical prescribing or funding advice.] Source

6.American College of Cardiology. New ACC Scientific Statement Details Role of Inflammation in CVD. 29 September 2025.[Official summary of the ACC's 2025 scientific statement.] Source

7.US Preventive Services Task Force. Cardiovascular Disease: Risk Assessment With Nontraditional Risk Factors. Final recommendation statement. 2018.[Older screening-outcome assessment, distinguished from the newer ACC position.] Source

8.MedlinePlus. Homocysteine Test. Source

9.Awanui Labs Wellington. Do I have to pay for my tests?[Regional guidance. Confirm local eligibility and charges before testing.] Source

Quick answers

What extra blood tests should I ask my GP for?

Start with your symptoms, family history and existing results. HbA1c, ferritin or targeted thyroid tests may help, but there is no single extra panel everyone needs.

Is fasting insulin better than fasting glucose?

Insulin can rise while glucose remains normal, but that does not make fasting insulin a better routine screening test. HbA1c and glucose tests remain useful for identifying prediabetes and diabetes.

Do I need a full thyroid panel?

Usually not as a first step. TSH is generally the starting test in adults. Free T4, free T3 and antibodies are added when results or the clinical situation justify them.

Will extra blood tests be funded in New Zealand?

Funding depends on eligibility, the reason for testing and local laboratory rules. Some wellness tests are patient-paid. Ask your GP or laboratory about charges before collection.

How often should I repeat blood tests?

Agree on timing for each test with your GP. Previous results, symptoms and treatment determine follow-up. A comprehensive panel every six to twelve months is not a default everyone needs.