Understanding Your
Blood Results
A plain-English guide to the most common tests we carry out at the practice — what they measure, what the numbers mean, and when to get in touch.
Full Blood Count (FBC)
A snapshot of the cells in your blood — usually the first test we do for fatigue, infections, or routine checks
What is it?
A full blood count looks at the three main types of cells in your blood: red blood cells (which carry oxygen around your body), white blood cells (which fight infection), and platelets (which help your blood clot). It gives us a lot of information in one go.
Key parts of the test
What the results mean
You may feel tired, breathless, or pale. Could be due to low iron, B12, or folate — or occasionally something else we'll want to investigate.
Often a sign your body is fighting an infection. Occasionally seen with inflammation. Very high levels need further investigation.
Can suggest low B12 or folate, or occasionally too much alcohol or thyroid problems. We may check your B12 and folate separately.
All three cell types are within the expected range. This is a reassuring finding and no further action is usually needed for the FBC alone.
A note from the practice: An abnormal FBC result doesn't usually mean something serious. Most of the time it points to something straightforward like low iron or a mild infection. We'll always contact you if we need to act on a result — if you haven't heard from us, your result is likely reassuring.
Kidney Function (U&Es / eGFR)
Checks how well your kidneys are filtering your blood — important for many medications and long-term health
What is it?
Your kidneys filter waste products from your blood and regulate fluid and salt balance. These tests measure how efficiently they're doing that job. The main numbers we look at are creatinine (a waste product), urea, and the eGFR — an estimate of your kidney filtering rate. We also check your sodium and potassium as part of the same profile.
Key parts of the test
What the results mean
Suggests the kidneys aren't filtering as efficiently as they should. Mild reduction is common and manageable — we'll monitor it and may need to adjust any medications.
Waste products building up. Sometimes this is temporary (dehydration, illness). If it persists, we'll investigate further and may refer you to a kidney specialist.
Your kidneys appear to be working well. eGFR above 60 with normal creatinine is a reassuring result.
Very high or very low potassium can affect heart rhythm. We may ask you to come in promptly for a repeat test or review of your medications.
A note from the practice: Kidney function can fluctuate slightly day-to-day depending on hydration and diet. One mildly abnormal result doesn't necessarily mean there's a kidney problem — we'll often repeat the test before taking further action. If you take regular medications, we check kidney function periodically to make sure they're still safe to use.
HbA1c — Blood Sugar (Glycated Haemoglobin)
The most important test for checking for diabetes or pre-diabetes — it gives a 3-month average of your blood sugar
What is it?
Unlike a finger-prick glucose test (which is a snapshot), HbA1c gives us your average blood sugar level over the past 2–3 months. It works by measuring how much sugar has attached to your haemoglobin. This makes it a much more reliable way to check for diabetes or to monitor how well diabetes is being managed. It doesn't require fasting.
Understanding the numbers
What the results mean
We'll contact you to discuss this and usually arrange a repeat test to confirm. Diabetes is very manageable — early detection and treatment make a big difference.
Your sugar is higher than ideal. With changes to diet and activity levels, many people bring this back into the normal range without ever developing diabetes.
Blood sugar is in the healthy range. We may recheck every 1–3 years as part of routine health monitoring, particularly if you have other risk factors.
We use HbA1c to track how well your diabetes is controlled. Most targets are between 48–58 mmol/mol depending on your situation and your medications.
A note from the practice: A raised HbA1c is not a crisis — it's a prompt to take action. Type 2 diabetes caught early responds very well to lifestyle changes, and many people manage it effectively for years with diet and exercise alone. We're here to support you through every step.
Cholesterol & Lipid Profile
A check of the fats in your blood that affect your risk of heart attack and stroke
What is it?
A lipid profile measures the different types of fat (lipids) in your blood. Not all cholesterol is bad — some types actually protect your heart. We look at the full picture, not just the total number, to work out your individual cardiovascular risk. Ideally this test is done fasting (nothing to eat for 9–12 hours beforehand).
Key parts of the test
What the results mean
Increases the risk of fatty deposits building up in arteries over time. Lifestyle changes and sometimes a statin medication can bring this down significantly.
Often linked to diet, alcohol, or diabetes. Above 4.4 means we can't calculate your LDL. Very high levels also carry a risk of pancreatitis.
Less of the protective cholesterol. Exercise and stopping smoking are the most effective ways to raise HDL levels.
Cholesterol levels are in a good range. Maintain a balanced diet with plenty of fruit, vegetables, and whole grains, and stay physically active.
A note from the practice: Cholesterol results need to be seen in context — your age, blood pressure, smoking status, and family history all affect how we interpret the numbers. A slightly raised cholesterol in a young, fit, non-smoker may need lifestyle advice only. The same level in someone with other risk factors might need medication. We'll always discuss the full picture with you.
Iron Studies & Ferritin
Checks your iron stores — one of the most common causes of tiredness, especially in women
What is it?
Iron is essential for making red blood cells. These tests check not just the iron circulating in your blood, but your body's iron stores (ferritin). You can have low iron stores and feel very tired even before anaemia shows up on a standard blood count. Iron studies also help us find out why your iron might be low — whether from diet, periods, gut absorption, or blood loss.
Key parts of the test
What the results mean
Your iron stores are depleted. Even without anaemia, low ferritin can cause fatigue, hair loss, poor concentration, and feeling run-down. Iron tablets or dietary changes are usually the first step.
Confirms iron deficiency. We'll want to understand why — in some patients we need to check for gut absorption issues or sources of blood loss.
Can be raised by inflammation, liver conditions, or (rarely) iron overload. We may arrange further tests depending on how high it is and your symptoms.
Iron levels and stores are in the healthy range. If you're still tired, we'll look at other possible causes — thyroid, B12, sleep, or other factors.
A note from the practice: Iron deficiency is extremely common, particularly in women of reproductive age and during pregnancy. If you've been told your iron is low, please don't ignore it — untreated iron deficiency can significantly affect your energy, mood, and concentration. Iron supplementation works well and we'll guide you on the best approach for you.
Folate (Folic Acid)
A B-vitamin essential for making red blood cells and for healthy cell division — especially important in pregnancy
What is it?
Folate is a B-vitamin (B9) found naturally in green leafy vegetables, beans, and citrus fruit. Your body uses it to make and repair DNA and to produce healthy red blood cells. It can't be stored in large quantities, so you need a regular supply through diet. It's often tested alongside B12 and iron when we're investigating tiredness, anaemia, or in early pregnancy. Low folate can cause a type of anaemia where red cells become abnormally large (macrocytic anaemia).
Key parts of the test
What the results mean
Can cause tiredness, mouth ulcers, and a type of anaemia. We'll usually start you on folic acid supplements (5mg daily) and look at the cause — diet, gut absorption, or medications like methotrexate or certain epilepsy drugs.
Very important to address promptly. Folate is essential in the first 12 weeks of pregnancy for normal development of the baby's spine and brain. We'll prescribe a higher dose supplement immediately.
Folate levels are adequate. If you are pregnant or planning to become pregnant, we still recommend 400 micrograms of folic acid daily as a supplement even with a normal level.
Not quite deficient, but lower than ideal. We may recommend dietary improvements and a supplement, particularly if you're feeling tired or have other risk factors.
A note from the practice: Low folate is very common and responds quickly to supplementation. Good dietary sources include spinach, broccoli, Brussels sprouts, chickpeas, and fortified breakfast cereals. If you're on long-term medication that affects folate absorption, we'll monitor this as part of your regular reviews. For anyone planning a pregnancy, folic acid supplementation is one of the most important things you can do.
Vitamin B12
Essential for your nervous system and red blood cell production — deficiency can creep up slowly but has real consequences
What is it?
Vitamin B12 is found almost exclusively in animal products — meat, fish, dairy, and eggs. Your body stores it in the liver for several years, which means deficiency develops slowly but can be well-advanced before symptoms appear. B12 is essential for making red blood cells and for keeping your nervous system healthy. Unlike most vitamins, it needs a special protein called intrinsic factor (made in the stomach) to be absorbed — so even a good diet isn't always enough.
Key parts of the test
What the results mean
Confirmed deficiency. Symptoms can include extreme tiredness, pins and needles, poor memory, mouth soreness, and low mood. Treatment depends on the cause — injections if absorption is the problem, or high-dose oral supplements otherwise.
May still be causing symptoms for some people. We'll consider the full picture — your symptoms, diet, and whether you're on medications like long-term PPIs or metformin, which reduce B12 absorption.
Levels are within the expected range. If you still have symptoms such as tingling or fatigue, we may check active B12 or other causes, as routine B12 can occasionally miss functional deficiency.
If you have pernicious anaemia (your stomach doesn't produce intrinsic factor), oral supplements won't work. You'll need B12 injections — usually every 3 months for life. We manage this at the practice.
A note from the practice: B12 deficiency is more common than people realise — particularly in people over 60, those following a vegan or vegetarian diet, and anyone on long-term metformin (for diabetes) or stomach acid tablets (PPIs). The neurological effects of prolonged deficiency can sometimes be irreversible, so we take low B12 seriously and treat it promptly. If you have B12 injections, please don't miss appointments — this is a lifelong treatment.
Thyroid Function (TSH & T4)
Checks whether your thyroid gland is overactive or underactive — a common and very treatable cause of tiredness, weight changes, and mood symptoms
What is it?
Your thyroid is a small butterfly-shaped gland in your neck that controls your body's metabolism — essentially the speed at which everything runs. It does this by producing hormones (T3 and T4). Your brain monitors thyroid hormone levels and sends a signal called TSH (thyroid stimulating hormone) to tell the gland how hard to work. TSH is the most sensitive early indicator of thyroid problems — often changing before T4 does. We test TSH routinely and add T4 (and sometimes T3) if the TSH is abnormal.
Key parts of the test
What the results mean
The brain is working hard to stimulate a sluggish thyroid. Symptoms include tiredness, weight gain, feeling cold, constipation, dry skin, low mood, and brain fog. Treated with a daily thyroxine tablet (levothyroxine) — most people feel much better once the dose is right.
The thyroid is producing too much hormone and the brain has backed off its signal. Symptoms include weight loss, racing heart, anxiety, sweating, tremor, and difficulty sleeping. Needs further investigation and usually specialist input.
TSH is mildly raised but T4 is still normal. You may or may not have symptoms. We'll monitor and sometimes treat, depending on how high TSH is, your symptoms, and whether thyroid antibodies are present.
Your thyroid is functioning normally. If you're still experiencing symptoms like fatigue or weight changes, we'll look at other possible causes — iron, B12, cortisol, blood sugar, or sleep.
A note from the practice: Thyroid conditions are among the most common hormonal problems we see — especially in women. The good news is they're very well managed once diagnosed. If you're on levothyroxine, we check your TSH once a year (or after any dose change) to make sure you're on the right amount. If your symptoms change, please let us know rather than waiting for your annual review — the dose sometimes needs adjusting over time.
Important: This information is for general guidance only and does not replace a conversation with your GP. If you have received a result and are concerned, or have not been contacted about a result you were expecting, please contact the practice. Always speak to your doctor before making changes to your medication or treatment.