Blood Tests Before and During Mounjaro or Wegovy: What UK Patients Should Know in 2026

Medicines such as Mounjaro and Wegovy have transformed the conversation around medical weight management in the UK.

Their use continues to expand, with NHS England implementing a phased rollout of tirzepatide, while the range of authorised weight-management treatments has also continued to develop during 2026.

As more people explore medically supervised weight management, one question is being asked increasingly often:

Do you need blood tests before taking Mounjaro, Wegovy or another GLP-1 weight-management medicine?

There is no single set of blood tests that every person must have simply because they use one of these medicines.

However, depending on your health, medication, treatment provider and medical history, a clinician may request blood tests before starting treatment or as part of ongoing monitoring.

Here is what UK patients should know.

What Are GLP-1 Weight-Management Medicines?

GLP-1 medicines mimic the action of glucagon-like peptide-1, a hormone involved in appetite, digestion and blood glucose regulation.

Some widely recognised medicines include semaglutide and liraglutide.

Tirzepatide, sold as Mounjaro, works slightly differently because it acts on both GIP and GLP-1 receptors.

For simplicity, these treatments are frequently discussed together when people talk about modern weight-management medicines.

Examples available in the UK include:

• Mounjaro — tirzepatide
• Wegovy — semaglutide
• Other GLP-1 medicines used for specific authorised indications

These are prescription-only medicines and should be obtained from a legitimate healthcare provider after an appropriate medical assessment.

Why Might Blood Tests Be Requested Before Treatment?

Your healthcare provider needs to understand more than your weight before deciding whether a particular medicine is appropriate.

Weight can be closely connected with several aspects of metabolic and cardiovascular health.

Depending on your history, symptoms and existing conditions, your clinician may want to assess areas such as:

• Blood glucose control
• Kidney function
• Liver function
• Cholesterol and triglycerides
• Thyroid function
• Nutritional status
• Other existing medical conditions

Blood testing can help provide objective information that complements your medical history, physical measurements and clinical assessment.

However, the tests required will vary from person to person.

Never order a collection panel solely because it appears on a generic online checklist. Your prescriber or healthcare provider should tell you which tests are appropriate.

1. HbA1c and Blood Glucose Tests

One of the most relevant areas of assessment is blood glucose.

An HbA1c test estimates your average blood glucose level over the previous two to three months.

It is widely used in the diagnosis and monitoring of type 2 diabetes and can also identify blood glucose levels that may warrant further assessment.

This information can be particularly relevant because some people seeking medical weight-management treatment also have:

• Type 2 diabetes
• Prediabetes or increased diabetes risk
• Metabolic health concerns
• Other weight-related conditions

If you already have diabetes, your prescriber may use glucose-related measurements as part of your ongoing clinical management.

Do not adjust diabetes medication based on a blood test result without consulting your healthcare professional.

2. Kidney Function Tests

Your clinician may also decide to assess kidney function.

A typical kidney or renal profile can include measurements such as:

• Creatinine
• Estimated glomerular filtration rate (eGFR)
• Urea
• Electrolytes such as sodium and potassium

Why might this matter?

Gastrointestinal side effects such as vomiting and diarrhoea can occur with GLP-1-related treatments. Significant fluid loss may cause dehydration, which can be particularly important for people with existing kidney problems.

Your prescriber can determine whether baseline or follow-up renal testing is appropriate based on your personal circumstances.

3. Liver Function Tests

Obesity and metabolic conditions can sometimes occur alongside liver problems, including metabolic dysfunction-associated steatotic liver disease.

A healthcare provider may therefore request liver blood tests as part of a broader health assessment.

Common measurements may include:

• ALT
• AST
• ALP
• Bilirubin
• Albumin

An abnormal liver test does not automatically identify a particular condition.

Results need to be interpreted alongside your medical history and, where necessary, further investigation.

4. Cholesterol and Lipid Profile

A lipid profile provides information about fats circulating in your blood.

It may include:

• Total cholesterol
• LDL cholesterol
• HDL cholesterol
• Triglycerides
• Non-HDL cholesterol

This can help your healthcare provider understand your broader cardiovascular and metabolic risk.

NHS England specifically lists dyslipidaemia among the weight-related health problems considered within current eligibility criteria for tirzepatide treatment for obesity in certain patients.

Your lipid results should be interpreted in the context of your overall cardiovascular health rather than considered in isolation.

5. Thyroid Blood Tests

Weight change can sometimes be associated with thyroid conditions, although thyroid problems are only one of many possible factors influencing body weight.

If there is a clinical reason to investigate thyroid function, your healthcare provider may request tests such as:

• Thyroid-stimulating hormone (TSH)
• Free thyroxine (FT4)

These tests can help assess how your thyroid gland is functioning.

A thyroid blood test is not automatically necessary for everyone considering medical weight management. The decision should be based on your symptoms, clinical history and your healthcare provider’s assessment.

6. Full Blood Count

A full blood count, or FBC, measures different types of cells within your blood.

These include:

• Red blood cells
• Haemoglobin
• White blood cells
• Platelets

It can provide useful general health information and may help identify problems such as anaemia or changes that warrant further investigation.

Your healthcare provider may include an FBC as part of a wider baseline health assessment, although this depends on individual clinical circumstances.

7. Vitamin and Nutritional Blood Tests

Significant changes in appetite and food intake can make nutritional quality particularly important during weight-management treatment.

Where clinically indicated, your healthcare professional may investigate nutritional markers such as:

• Vitamin B12
• Folate
• Vitamin D
• Ferritin and iron markers

These tests are not universally required for people taking Mounjaro or Wegovy.

They may be more appropriate where there are symptoms, dietary concerns, existing deficiencies or other clinical reasons to investigate.

Do You Need Blood Tests Before Starting Mounjaro?

There is no universal blood-test panel that every person must complete before receiving Mounjaro.

An appropriate prescriber should first undertake a medical assessment and determine what additional investigations are required.

Some people may require several blood tests because of existing health conditions. Others may require fewer investigations.

This is why personalised medical assessment is more appropriate than purchasing a generic “Mounjaro blood panel” without clinical guidance.

Do You Need Blood Tests While Taking Mounjaro or Wegovy?

Again, this depends on the individual.

Your healthcare provider may arrange follow-up testing when there is a clinical reason to monitor:

• Diabetes control
• Kidney function
• Liver health
• Cholesterol
• Nutritional status
• Existing medical conditions
• Other medications

Blood tests form only one part of monitoring.

Your prescriber may also monitor factors such as your weight, symptoms, side effects, nutrition, blood pressure and overall response to treatment.

GLP-1 Safety Is Particularly Important in 2026

The rapidly growing popularity of weight-management medication has also led UK regulators to increase public-safety messaging.

The Medicines and Healthcare products Regulatory Agency has warned people against obtaining prescription weight-loss medicines from illegal or unregulated sellers and stresses that these treatments should be supplied following appropriate clinical assessment.

The MHRA also strengthened warnings concerning acute pancreatitis associated with GLP-1 receptor agonists and dual GIP/GLP-1 medicines in early 2026.

Patients experiencing severe or persistent symptoms should seek appropriate medical advice rather than relying on routine blood testing or attempting to adjust their treatment themselves.

What Changed With Weight-Management Medicines in 2026?

The subject has remained particularly prominent this year.

NHS implementation of tirzepatide continues through a phased approach, prioritising eligible patients with higher clinical need.

The MHRA also approved additional semaglutide options during 2026, including a higher-dose Wegovy injection for certain adults with obesity and, in June 2026, the UK’s first GLP-1 tablet authorised for weight management.

These developments mean more people are likely to have conversations with healthcare professionals about appropriate medical weight management — and, where clinically appropriate, the blood tests that support those assessments.

Can You Have Your Blood Tests Collected at Home?

If your prescriber, GP, private clinic or testing provider has requested blood tests, travelling to a clinic is not always necessary simply to have your sample collected.

Professional mobile phlebotomy allows a trained phlebotomist to visit your:

• Home
• Workplace
• Care setting
• Other suitable location

Your blood can then be collected according to the test instructions and prepared for the appropriate laboratory.

This can be useful if you are receiving care through a private weight-management provider that sends you a blood-test request or testing kit but does not provide a convenient local blood-draw service.

Mobile Blood Tests in Manchester and Cheshire

BloodSample360 provides professional mobile blood sample collection throughout Greater Manchester and Cheshire.

Our service can be particularly convenient for people who:

• Have received a blood-test request from a private clinic
• Have a private testing kit requiring venous blood collection
• Need repeat blood tests
• Work long hours
• Have difficulty travelling to clinics
• Prefer having their sample collected privately at home

BloodSample360 supports clients across areas including Manchester, Salford, Stockport, Chester, Crewe and surrounding locations.

You should have your blood-test request form or private testing kit available before your appointment.

BloodSample360 performs the professional blood collection; medical interpretation, diagnosis and treatment remain the responsibility of your doctor, prescriber or healthcare provider.

How to Prepare for Your Blood Collection

Before your appointment, check the instructions supplied by your healthcare provider or laboratory.

Check Whether You Need to Fast

Not every blood test requires fasting.

If fasting is required, your test provider should tell you how long to fast and whether you can drink water.

Do not fast unnecessarily.

Drink Water Unless Told Otherwise

Being appropriately hydrated can make venous blood collection easier for some people.

Follow any specific fluid instructions provided for your tests.

Have Your Documentation Ready

Keep your:

• Blood-test request form
• Private test kit
• Identification if required
• Laboratory paperwork

ready before the phlebotomist arrives.

Do Not Stop Medication Without Medical Advice

Do not stop Mounjaro, Wegovy, diabetes medication or any other prescribed treatment simply because you are having a blood test.

Ask your prescriber if medication timing matters for your specific test.

Frequently Asked Questions

What blood tests do I need before Mounjaro?

There is no single compulsory panel for everyone. Depending on your circumstances, a healthcare provider may assess blood glucose, kidney function, liver function, cholesterol or other markers. Your prescriber should determine which tests you require.

Do I need an HbA1c test before Mounjaro?

Some patients may have HbA1c measured, particularly when diabetes or blood-glucose status is relevant. It is not appropriate to assume every patient requires exactly the same testing.

Do you need liver tests while taking Wegovy?

A clinician may request liver tests when clinically appropriate, but routine testing requirements depend on your individual circumstances.

Can I arrange my own blood draw if my online clinic sends me a testing kit?

Yes, provided the kit is suitable for professional mobile collection and you have the required documentation. Contact the phlebotomy provider beforehand if you are unsure about the tubes, sample handling or laboratory-return requirements.

Does BloodSample360 prescribe Mounjaro or Wegovy?

No. BloodSample360 provides mobile phlebotomy and blood sample collection. Prescription medicines must be discussed with an appropriately qualified healthcare provider.

Can BloodSample360 tell me whether my results are normal?

BloodSample360’s role is blood sample collection. Results and medical interpretation should be discussed with the clinician, GP, laboratory or private provider responsible for your tests.

Book Your Mobile Blood Collection in Manchester or Cheshire

The growth of medical weight-management treatments means more people are undergoing health assessments and blood tests through GPs, private clinics and specialist providers.

Getting the required blood sample collected does not need to mean rearranging your entire day around a clinic appointment.

If your healthcare provider has requested blood tests before or during Mounjaro, Wegovy or another weight-management treatment, BloodSample360 can provide professional mobile blood collection at your home or workplace.

We serve clients across Greater Manchester, Cheshire and surrounding areas.

Have your blood-test request form or private testing kit available and book your BloodSample360 mobile phlebotomy appointment today.

This article provides general information and is not medical advice. Mounjaro, Wegovy and similar medicines are prescription-only treatments. Decisions about suitability, blood testing, dosage and monitoring should be made by an appropriately qualified healthcare professional.