Weight Loss Blood Test, from our experts to you.
Dr Sam Rodgers MBBS, MRCGP

Chief Medical Officer meet our doctors

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Why am I not
losing weight?

Losing weight is never easy, and it can be difficult at the best of times to get into the right frame of mind to embark upon a weight loss programme. If you are tired, lack energy, or suffer from low mood and lack of motivation, then losing weight can be even more of a struggle.


What can I learn
from this test?

Our weight loss profile investigates possible causes for your weight loss stalling or gaining weight unexpectedly. It also looks at health markers like cholesterol and liver health, which help you understand your health status and risk for certain conditions.

Key tests include iron and vitamin D to help identify why you might lack the energy and motivation to stick with your diet and thyroid function to see if your metabolism is causing you to gain weight. Cortisol and diabetes markers help identify if stress or metabolic disease is causing you to store weight around your middle.


Can hormones
affect weight gain?

For both men and women, changes in hormone balance can affect body composition and weight control.

Our test also looks at testosterone, oestradiol, and FSH to assess whether a woman might be menopausal. You can learn more about how hormones may affect your weight in our blog: Are your female hormones sabotaging your weight loss?


What's included?

Adrenal hormones
Cholesterol status
Diabetes
Hormones
Inflammation
Iron status
Liver health
Muscle health
Thyroid hormones
Vitamins
Select profile for more information

Cortisol Cortisol is a stress hormone produced by the adrenal glands. It is vital to survival given its role in functions such as immunity, regulating blood pressure and releasing insulin for blood sugar maintenance.
Total Cholesterol Cholesterol is an essential fat (lipid) in the body. Although it has a bad reputation it has some important functions, including building cell membranes and producing a number of essential hormones including testosterone and oestradiol. Cholesterol is manufactured in the liver and also comes from the food we eat. Although there are a number of different types of cholesterol, the two main components of total cholesterol are HDL (high density lipoprotein) which is protective against heart disease and LDL (low density lipoprotein) which, in high levels, can contribute to cardiovascular disease. Your total cholesterol result on its own is of limited value in understanding your risk of heart disease; high levels of HDL cholesterol can cause a raised total cholesterol result but may actually be protective against heart disease. Equally, you can have a normal total cholesterol level but have low levels of protective HDL cholesterol. The most important factors are how much HDL and LDL cholesterol you have, and what proportion of your total cholesterol is made up of protective HDL cholesterol. We give a detailed breakdown of the components of your total cholesterol in the rest of this cholesterol profile.
LDL Cholesterol LDL cholesterol (low-density lipoprotein) is a molecule made of lipids and proteins which transports cholesterol, triglycerides and other fats to various tissues throughout the body. Too much LDL cholesterol, commonly called 'bad cholesterol', can cause fatty deposits to accumulate inside artery walls, potentially leading to atherosclerosis and heart disease.
Non HDL Cholesterol Your total cholesterol is broken down into 2 main components; HDL (good) cholesterol and LDL (bad). There are more types of harmful cholesterol in your blood than just LDL - these include VLDL (very low-density lipoproteins) and other lipoproteins which are thought to be even more harmful than LDL cholesterol. Non-HDL cholesterol is calculated by subtracting your HDL cholesterol value from your total cholesterol. It therefore includes all the non-protective and potentially harmful cholesterol in your blood, not just LDL. As such, it is considered to be a better marker for cardiovascular risk than total cholesterol and LDL cholesterol. The recommended level of non-HDL cholesterol is below 4 mmol/L.
HDL Cholesterol HDL cholesterol (high-density lipoprotein) is a molecule in the body which removes cholesterol from the bloodstream and transports it to the liver where it is broken down and removed from the body in bile. HDL cholesterol is commonly known as 'good cholesterol'.
Total Cholesterol : HDL The cholesterol/HDL ratio is calculated by dividing your total cholesterol value by your HDL cholesterol level. It is used as a measure of cardiovascular risk because it gives a good insight into the proportion of your total cholesterol which is good (i.e. high-density lipoprotein HDL). Heart disease risk tools (such as QRisk) use the cholesterol/HDL ratio to calculate your risk of having a heart attack.
Triglycerides Triglycerides are a type of fat (lipid) that circulate in the blood. After you eat, your body converts excess calories (whether from fat or carbohydrates) into triglycerides which are then transported to cells to be stored as fat. Your body then releases triglycerides when required for energy.
HbA1c Haemoglobin A1c (HbA1c), also known as glycated haemoglobin, is a longer term measure of glucose levels in your blood than a simple blood glucose test. Glucose attaches itself to the haemoglobin in your red blood cells, and as your cells live for around 12-16 weeks, it gives us a good indication of the average level of sugar in your blood over a 3 month period.
FSH Follicle Stimulating Hormone (FSH) is produced in the pituitary gland and is important for women in the production of eggs by the ovaries and for men for men in the production of sperm. In the first half of the menstrual cycle in women, FSH stimulates the enlargement of follicles within the ovaries. Each of these follicles will help to increase oestradiol levels. One follicle will become dominant and will be released by the ovary (ovulation), after which follicle stimulating hormone levels drop during the second half of the menstrual cycle. In men, FSH acts on the seminiferous tubules of the testicles where they stimulate immature sperm cells to develop into mature sperm.
Oestradiol Oestradiol is a female steroid hormone, produced in the ovaries of women and to a much lesser extent in the testes of men. It is the strongest of three oestrogens and is responsible for the female reproductive system as well as the growth of breast tissue and bone thickness. In pre-menopausal women, oestradiol levels vary throughout the monthly cycle, peaking at ovulation. In women, oestradiol levels decline with age, culminating with the menopause when the ovaries stop producing eggs. Low oestradiol can cause many symptoms associated with the menopause, including hot flushes, night sweats and mood swings. Low oestradiol can also cause osteoporosis.
Testosterone Testosterone is a hormone that causes male characteristics. For men, it helps to regulate sex drive and has a role in controlling bone mass, fat distribution, muscle mass, strength and the production of red blood cells and sperm. Testosterone is produced in the testicles of men and, in much smaller amounts, in the ovaries of women. Testosterone levels in men naturally decline after the age of 30, although lower than normal levels can occur at any age and can cause low libido, erectile dysfunction, difficulty in gaining and maintaining muscle mass and lack of energy. Although women have much lower amounts of testosterone than men, it is important for much the same reasons, playing a role in libido, the distribution of muscle and fat and the formation of red blood cells. All laboratories will slightly differ in the reference ranges they apply because they are based on the population they are testing. The normal range is set so that 95% of men will fall into it. For greater consistency, we use the guidance from the British Society for Sexual Medicine (BSSM) which advises that low testosterone can be diagnosed when testosterone is consistently below the reference range, and that levels below 12 nmol/L could also be considered low, especially in men who also report symptoms of low testosterone or who have low levels of free testosterone.
hs - CRP
Iron Iron is a mineral that is essential for life. It is a component of haemoglobin, a protein in our red blood cells that is responsible for transporting oxygen around our body. If we don't have enough iron, our haemoglobin levels fall and we can't get sufficient oxygen to our cells. This can cause symptoms which include fatigue, dizziness, and shortness of breath. Serum iron is a very transient reading and can be influenced by the amount of iron-rich food in your diet in the days before your blood test. For this reason, iron is rarely looked at on its own, and is interpreted alongside other markers in an iron status test.
TIBC Total iron-binding capacity (TIBC) is a measure of the ability of your body to efficiently carry iron through the blood.
Transferrin Saturation Transferrin is made in the liver and is the major protein in the blood which binds to iron and transports it round the body. This test measures how much this protein is 'saturated' by iron.
Ferritin Ferritin is a protein which stores iron in your cells and tissues. Usually, the body incorporates iron into haemoglobin to be transported around the body, but when it has a surplus, it stores the remaining iron in ferritin for later use. Measuring ferritin levels gives us a good indication of the amount of iron stored in your body.
Bilirubin Bilirubin is a product of the breakdown of haemoglobin from red blood cells. It is removed from the body via the liver, stored and concentrated in the gallbladder and secreted into the bowel. It is removed from your body through urine and faeces. Bilirubin causes the yellowish colour you sometimes see in bruises, due to red blood cells breaking down underneath the skin.
ALP Alkaline phosphatase (ALP) is an enzyme found mainly in the liver and bones. Measuring it can indicate ongoing liver, gallbladder or bone disease.
ALT Alanine transferase (ALT) is an enzyme which is mostly found in the liver, but is also found in smaller amounts in the heart, muscles and the kidneys. If the liver is damaged, ALT is leaked into to bloodstream. As ALT is predominantly found in the liver, it is usually an accurate marker for liver inflammation and can indicate liver damage caused by alcohol, fatty liver, drugs or viruses (hepatitis).
GGT Gamma GT, also known as gamma-glutamyl transferase (GGT), is a liver enzyme which is raised in liver and bile duct diseases. It is used in conjunction with ALP to distinguish between bone or liver disease. Gamma GT is also used to diagnose alcohol abuse as it is raised in 75% of long term drinkers.
Creatine kinase Creatinine kinase (CK) is an enzyme which is necessary for muscle function and is found in the heart and skeletal muscles as well as other tissues. It signifies muscle cell damage and death and is measured to diagnose and monitor muscle damage. CK levels tend to be higher in people with greater muscle mass.
TSH Thyroid stimulating hormone (TSH) is produced in the pituitary gland in order to regulate the production of thyroid hormones thyroxine (T4) and triiodothyronine (T3) by the thyroid gland. If thyroid hormones in the blood are low, then more TSH is produced to stimulate the thyroid gland to produce more of them. If thyroid hormone levels are high, then the pituitary produces less TSH to slow the production of thyroid hormones. If TSH is too high or too low, it normally signifies that there is a problem with the thyroid gland which is causing it to under or over produce thyroid hormones. Sometimes a disorder of the pituitary gland can also cause abnormal TSH levels.
Free Thyroxine Thyroxine (T4) is one of two hormones produced by the thyroid gland. It works to speed up the rate of your metabolism. Most T4 is bound to carrier proteins in the blood - it is only the free, or unbound, T4 that is active in the body, which is measured in this test. Free T4 is the less active of the two main thyroid hormones. To have an impact on your cells it needs to convert to the more active T3 when your body needs it.
Vitamin D Although called a vitamin, vitamin D is actually a hormone which is activated by sunshine on your skin. Vitamin D is essential for bone strength as it helps your intestines absorb calcium. However, it is thought that vitamin D also plays an important role in immune function, as well as in many chronic diseases and mental health. Many people in the UK have low levels of vitamin D with symptoms including muscle weakness, mood swings and fatigue. People who have dark skin, as well as those who don't spend much time outdoors are particularly at risk of low vitamin D. Small amounts of vitamin D can be obtained from food, especially oily fish, eggs and any food which has been fortified with vitamin D. If you are deficient in vitamin D you are unlikely to be able to improve your levels by food alone.

How to prepare
for your test

Special instructions

Prepare for your Weight Loss Blood Test by following these instructions. Please take your sample before 10am. Take this test when any symptoms of short-term illness have settled. Avoid heavy exercise for 48 hours beforehand. Avoid fatty foods for eight hours before your test, you do not need to fast. Take this test two to five days after the start of your period, ideally on day three. It can be taken any time if you do not have periods. Hormonal contraception can affect this test, taking a break from this and using barrier contraception will give more accurate results. Corticosteroid medication can affect this test, ask your doctor whether to stop before testing. Avoid taking your sample from a finger used to apply hormone gels/pessaries in the past 4 weeks. Use gloves to apply these. You should take this test before you take any medication or vitamin/mineral supplements. Do not take biotin supplements for two days before this test, discuss this with your doctor if it is prescribed.


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