Most people start losing weight through diet and exercise, and only have tests when their weight stops falling. The order should be reversed. Blood tests before weight loss answer three questions: whether there is a medical cause of excess weight that needs treatment (because without it, the diet will not work), whether it is safe for your body to be in a calorie deficit, and what your baseline is, against which progress can be compared after 3 and 6 months. A clinical dietitian will request these tests at your first appointment anyway; bringing your results with you shortens the wait for a meal plan by several weeks. The result report is issued in Polish.
Tests that explain why your weight is not falling
TSH, FT4, anti-TPO
Hypothyroidism slows your metabolism, causes water retention and leaves you with less energy for physical activity. It is common, especially in women, and can be treated effectively. TSH is a screening test; FT4 shows whether hypothyroidism is overt, while anti-TPO points to Hashimoto’s thyroiditis. Without bringing thyroid function under control, even a well-planned weight-loss programme produces poor results.
Glucose, insulin, HOMA-IR, HbA1c
Insulin resistance is a condition in which cells respond poorly to insulin, the pancreas produces more of it, and high insulin levels promote fat storage and make it harder to burn fat. Fasting glucose and insulin measurements allow the HOMA-IR index to be calculated. Glycated haemoglobin (HbA1c) shows average blood glucose over 3 months and detects prediabetes. For people with insulin resistance, diets with a lower glycaemic load and strength training are more effective; this changes the strategy, so it is worth knowing at the outset.
Lipid profile
Total cholesterol, LDL, HDL and triglycerides (optionally non-HDL and ApoB). High triglycerides with low HDL are a typical pattern in metabolic syndrome. A lipid profile before dieting and after 3 months is the best evidence that lifestyle changes are working, and is more motivating than the scales.
Serum cortisol
Chronic stress and insufficient sleep raise cortisol, which promotes abdominal obesity and bouts of hunger. A morning blood cortisol test provides an initial indication; if Cushing’s syndrome is suspected, your doctor will request dynamic tests. It is worth measuring when fat accumulates mainly around the abdomen and the back of the neck, and stretch marks, hypertension and insomnia are present.
Prolactin, sex hormones
In women with irregular menstrual cycles, acne and male-pattern hair growth, PCOS needs to be ruled out (testosterone, SHBG, DHEA-S, LH, FSH). Men with abdominal obesity and reduced energy often have low testosterone, creating a vicious circle: obesity lowers testosterone, and testosterone deficiency promotes obesity.
Safety checks before a calorie deficit
Full blood count, ferritin, vitamin B12, folate (folic acid)
A calorie deficit means less food, and therefore less iron and fewer vitamins. Someone starting a weight-loss diet with low ferritin will quickly develop anaemia, which saps the energy needed for exercise and increases appetite. It is worth correcting deficiencies before starting the diet or alongside it.
Vitamin D
Obesity is associated with lower 25-OH-D levels (the vitamin dissolves in fatty tissue). Deficiency reduces muscle strength and worsens mood, while supplementation is inexpensive and safe when levels are monitored.
Liver function tests: ALAT, ASPAT, GGT
Most people with abdominal obesity have fatty liver disease. Raised ALAT and GGT before dieting are a reason to limit fructose and alcohol; their return to normal after a few months is one of the earliest effects of weight loss. Very rapid weight loss (more than 1–1.5 kg per week) can temporarily worsen liver function test results and promote gallstones, so monitoring during the process makes sense.
Creatinine, eGFR, uric acid, electrolytes
High-protein and ketogenic diets put a strain on the kidneys and raise uric acid; they need to be modified for people with gout or kidney disease. Sodium and potassium matter when following low-carbohydrate diets, which increase the excretion of water and electrolytes (hence the “keto flu”).
Urinalysis
An inexpensive test that detects proteinuria, glucose in the urine and ketones, as well as urinary tract infections, which are more common in diabetes.
How to use the results
| Result | What it changes in your weight-loss plan |
|---|---|
| Raised TSH | thyroid treatment first, then diet; recheck TSH after 6–8 weeks |
| High insulin, HOMA-IR | lower glycaemic load, regular meals, strength training and possibly medical treatment |
| Low ferritin, B12 | supervised supplementation, a diet rich in iron and B12, repeat testing after 3 months |
| High ALAT, GGT | limit alcohol and fructose, keep weight loss to 0.5–1 kg/week |
| High uric acid | take care with high-protein diets and fasting, drink plenty of fluids |
When to repeat the tests
After 3 months: lipid profile, glucose, insulin, liver function tests, full blood count and ferritin (if it was low at baseline). After 6–12 months, the full set. If you are taking medicines to support weight loss (e.g. GLP-1 analogues), your doctor will set an individual monitoring schedule. Results should be interpreted by a doctor or clinical dietitian; this article does not replace a consultation.
Preparing for the tests
Have the tests in the morning, on an empty stomach (12 hours without food), after a good night’s sleep, with no alcohol for 3 days and no intense exercise the day before. In the preceding days, eat your normal diet, without fasting or “cleanses”, which will distort glucose, insulin and lipid results. Cortisol and prolactin tests require 30 minutes of rest before blood collection.
Starting to lose weight or work with a dietitian? Have baseline tests without a referral; the results will be useful at your first appointment:
- Obesity test package I – metabolic tests before weight loss
- Obesity test package II – extended version
- Dietitian test package – a set of tests requested by dietitians before preparing a meal plan
- Thyroid test panel – TSH, FT4
Buy online at BadamySie.pl, have your blood collected without a referral at one of more than 800 ALAB, Synevo and ETER-MED collection points across Poland, and access your results online. Collection point addresses: blood tests near you.
Frequently asked questions
Are tests necessary if I only want to lose 5 kg?
They are not compulsory, but TSH, glucose, a lipid profile and a full blood count are a small expense in return for ruling out causes that would prevent you from achieving results.
How often does a dietitian request tests?
Usually before the first appointment and after 3 months; more often if you have coexisting conditions.
Can I have these tests without a referral?
Yes, all the tests listed and ready-made packages for people who are overweight can be bought online and carried out at a collection point without a referral.
Sources
- Polskie Towarzystwo Leczenia Otyłości (Polish Society for the Treatment of Obesity), Zalecenia kliniczne dotyczące postępowania u chorych na otyłość 2024 (Clinical recommendations for the management of patients with obesity 2024), 2024. ptlo.org.pl
- Busetto L. et al., EASO, Nature Medicine, A new framework for the diagnosis, staging and management of obesity in adults, 2024. nature.com
- Wharton S. et al., Obesity Canada, CMAJ, Obesity in adults: a clinical practice guideline, 2020. cmaj.ca
Where can I get blood tests without a referral?
Blood collection centres with addresses and opening hours: Warszawa · Wrocław · Łódź · Kraków · Poznań · Gdańsk · Szczecin · Bydgoszcz · all cities.
Order your tests online at BadamySie.pl and have them done at a centre of your choice.