GLP-1 Medicines for Weight Loss: What You Need to Know

You may have heard people talking about GLP-1 medicines, weight loss injections, Mounjaro, or Wegovy. Over the last few years, GLP-1 medicines have become an important part of the conversation around weight management. Research has shown that medicines such as semaglutide and tirzepatide can produce significant weight loss when used alongside lifestyle changes.

But losing weight is not only about watching the number on the scales. So, what exactly are GLP-1 medicines, and why might blood tests be useful during a weight loss journey at MDX Victoria (Medical Diagnosis Victoria)?

What Are GLP-1 Medicines?

GLP-1 stands for glucagon-like peptide-1. It is a hormone naturally produced by the body, particularly after eating.

GLP-1 medicines work by acting on pathways involved in appetite, fullness, and blood sugar regulation. Some medicines, such as semaglutide, act mainly through the GLP-1 receptor, while tirzepatide acts on both GLP-1 and GIP receptors.

Clinical trials have shown that these medicines can lead to substantial weight loss:

• In the STEP 1 trial, adults with overweight or obesity who received weekly semaglutide alongside lifestyle intervention lost an average of 14.9% of their starting body weight over 68 weeks, compared with 2.4% with placebo, alongside improvements in several cardiometabolic risk factors.
• In the SURMOUNT-1 trial, tirzepatide was also associated with substantial weight loss and improvements in several metabolic risk factors, including blood pressure, triglycerides, and fasting insulin.

But what happens inside the body while that weight is coming off?

Weight Loss Is More Than a Number

Imagine two people both lose 10 kg. The weighing scales show the same result. But their blood results could tell a different story.

Blood tests can provide information about blood sugar, cholesterol, liver function, kidney function, thyroid hormones, and blood cells. Looking at these markers can help give a wider picture of someone’s health alongside their weight, symptoms, medical history, and lifestyle. This is where a Weight Loss / GLP-1 Profile can be useful.

What Does a Weight Loss / GLP-1 Profile Check?

At Medical Diagnosis Victoria, our Weight Loss / GLP-1 Profile includes a range of blood tests covering several areas of health:

• Blood sugar and metabolism: HbA1c gives an indication of average blood glucose levels over approximately the previous 2-3 months. This can be particularly relevant for people with obesity, pre-diabetes, or type 2 diabetes, and for people who are making significant lifestyle or weight changes. Research into GLP-1 medicines has shown improvements in measures such as blood glucose and HbA1c in relevant patient groups.
• Liver health: The profile includes ALT, AST, GGT, and bilirubin. The liver plays an important role in metabolism, and liver problems such as metabolic dysfunction-associated fatty liver disease are closely linked with obesity and metabolic health. Research has found that GLP-1 receptor agonists can be associated with improvements in some liver enzymes, particularly ALT and GGT, in people with metabolic liver disease. This does not mean that GLP-1 medicines are a treatment for every liver condition. Instead, liver markers can form part of the bigger picture when monitoring someone’s health.
• Pancreatic health: The profile also includes amylase and lipase, which are enzymes associated with the pancreas. These results should not be interpreted on their own. If someone develops symptoms that could indicate a pancreatic problem, clinical assessment is important. The reason we include these markers in the profile is to provide additional information that can be considered alongside symptoms, medical history, and other results.
• Kidney function: Urea, creatinine, uric acid, and eGFR provide information about kidney function. Kidney health is an important part of general metabolic health. It can also be particularly relevant if someone experiences significant vomiting or diarrhoea during treatment, as these symptoms can contribute to dehydration. Research has also investigated kidney outcomes in people receiving GLP-1 receptor agonists, although much of the evidence comes from people with diabetes or established cardiovascular/kidney risk.
• Thyroid function: The profile includes TSH and FT4, which are thyroid hormones involved in regulating metabolism and energy. Thyroid testing may be useful when clinically indicated, particularly when someone has symptoms or a medical history that raises the possibility of thyroid dysfunction.
• Cholesterol and cardiovascular health: The profile measures total cholesterol, HDL cholesterol, LDL cholesterol, and triglycerides. These are important markers when looking at cardiovascular and metabolic health. Clinical trials of GLP-1-based medicines have reported changes in several cardiometabolic risk factors, including lipid measures and blood pressure.
• Full Blood Count (FBC): An FBC measures red blood cells, white blood cells, and platelets. It is not a specific GLP-1 test, but it can provide useful information about general health and may help identify issues such as anaemia or changes in blood cell counts.

What About the Weight Loss / GLP-1 Profile Plus?

Sometimes you may want to look a little further. The Weight Loss / GLP-1 Profile Plus includes everything in the standard profile, together with:

• Vitamin B12
• Vitamin D
• Leptin

Vitamin B12 is important for normal blood formation and nervous system function. Vitamin D is important for bone health, immune function, and normal physiological processes. Research has also found an association between obesity and lower vitamin D concentrations, while systematic reviews suggest that vitamin D status can change during weight loss.

The Profile Plus also includes leptin, a hormone involved in appetite regulation and energy balance. These additional tests can provide further information in selected individuals, but results should always be interpreted in the context of the person’s overall health rather than being used on their own to explain weight gain or difficulty losing weight.

Who Might Consider a Weight Loss / GLP-1 Profile?

The profile may be suitable for people who are:

• Considering starting a GLP-1 medicine
• Already using a GLP-1 medicine
• Following a medically guided weight loss programme
• Managing obesity, pre-diabetes, or type 2 diabetes
• Experiencing significant changes in weight or metabolism
• Following a non-medicated weight loss programme
• Interested in checking important metabolic and general health markers

It is important to remember that not everyone needs the same tests. The appropriate investigations depend on your medical history, symptoms, medication, risk factors, and clinical assessment.

Weight Loss Should Be About Health Too

GLP-1 medicines can be an effective treatment option for some people, but they are not simply a quick solution for losing weight. They work best as part of an overall approach to weight management, which may include nutrition, physical activity, and appropriate clinical support.

They can also cause side effects. Gastrointestinal symptoms such as nausea, vomiting, and diarrhoea are among the common side effects reported with GLP-1 medicines, and these can sometimes lead to dehydration. More serious adverse effects, including acute pancreatitis, have also been reported. That is why weight management should focus on the whole person rather than the scales alone.

Medical Diagnosis Weight Loss / GLP-1 Profiles

At Medical Diagnosis Victoria, our blood-test profiles are designed to provide a broader picture of important health markers during a weight management journey.

• Weight Loss / GLP-1 Profile – £125: Includes testing of blood sugar, liver and pancreatic markers, kidney function, thyroid function, cholesterol, and a Full Blood Count.
• Weight Loss / GLP-1 Profile Plus – £173: Includes all of the above, together with Vitamin B12, Vitamin D, and Leptin.

Both profiles require an 8 to 12 hour fast before the blood sample. The standard profile has a stated same-day turnaround time, while the Profile Plus has a stated turnaround time of 20 working days. Results should always be interpreted alongside your medical history, clinical assessment, and any symptoms you may have.

Because weight loss is not just about seeing a smaller number on the scales. It is also about understanding your health along the way.

Ready to Monitor Your Weight Loss Journey?

Book your profile or speak with our clinical team today.

Frequently Asked Questions (FAQs)

Scholarly References

1. Wilding JPH, et al. (2021). Once-Weekly Semaglutide in Adults with Overweight or Obesity. New England Journal of Medicine, 384, 989-1002. DOI: 10.1056/NEJMoa2032183.
2. Jastreboff AM, et al. (2022). Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine, 387, 205-216. DOI: 10.1056/NEJMoa2206038.
3. Rezaei S, et al. (2021). GLP-1 Receptor Agonist Effects on Lipid and Liver Profiles in Patients with Nonalcoholic Fatty Liver Disease: Systematic Review and Meta-Analysis.
4. Zhu L, et al. (2021). Efficacy and Safety of GLP-1 Receptor Agonists in Patients With Type 2 Diabetes Mellitus and Non-Alcoholic Fatty Liver Disease: A Systematic Review and Meta-Analysis.
5. Mallard SR, et al. (2016). Vitamin D status and weight loss: a systematic review and meta-analysis of randomized and nonrandomized controlled weight-loss trials. American Journal of Clinical Nutrition, 104(4), 1151-1159. DOI: 10.3945/ajcn.116.136879.