7 Critical Blood Tests Everyone Should Ask For

Your body does not always shout when something is wrong.

Sometimes it whispers.

You may feel tired and blame work. You may feel dizzy and blame stress. You may gain belly fat and blame age. You may feel weak and say, “Maybe I need more sleep.”

Sometimes, yes, it is sleep. Sometimes it is stress. Sometimes it is food.

But sometimes your blood is already showing signs that something needs attention.

That is why blood tests are useful. They help you see what may be happening inside your body before symptoms become serious.

This does not mean you need to panic or test everything every week. It means you should know the important tests to discuss with your doctor, especially if you have symptoms, family history, high blood pressure, diabetes risk, tiredness, or unexplained changes in your body.

Here are 7 critical blood tests everyone should know about.

Full Blood Count

A full blood count, also called FBC, is one of the most common blood tests.

It checks the main cells in your blood, including red blood cells, white blood cells, haemoglobin, and platelets.

Red blood cells carry oxygen around your body.

Haemoglobin is the oxygen-carrying protein inside red blood cells.

White blood cells help your body fight infection.

Platelets help your blood clot when you bleed.

This test can help show if you have anaemia, infection, inflammation, or blood cell problems.

If your haemoglobin is low, you may feel tired, weak, dizzy, short of breath, or look pale. Some people blame these symptoms on stress, but low iron or anaemia may be involved.

If your white blood cells are high, your body may be fighting infection or inflammation. If they are too low, your doctor may want to check why.

If your platelets are too low, you may bruise or bleed more easily. If they are too high, your doctor may need to investigate further.

A full blood count is basic, but it gives a lot of useful information.

Ask about it if you feel constantly tired, weak, dizzy, breathless, pale, or you keep getting infections.

HbA1c

HbA1c checks your average blood sugar over the past 2 to 3 months.

This is different from a one-time blood sugar test.

A fasting blood sugar test tells you what your sugar level looks like at one moment. HbA1c gives a bigger picture.

It helps show whether your body has been handling blood sugar well over time.

This matters because high blood sugar can develop quietly. Many people with prediabetes do not feel obvious symptoms at first.

You may still go to work, eat normally, and feel okay while your blood sugar is slowly rising.

HbA1c is useful for checking diabetes risk, prediabetes, and long-term blood sugar control.

You should discuss it with your doctor if you have:

Family history of type 2 diabetes
High blood pressure
Belly fat
Frequent thirst
Frequent urination
Blurred vision
Tiredness after meals
Slow wound healing

Food, sleep, stress, weight, physical activity, and family history can all affect blood sugar.

The earlier you catch blood sugar problems, the more chance you have to make changes before things become serious.

Fasting Insulin

Fasting insulin is not always included in routine checks, but it can be useful for some people.

Insulin is the hormone that helps move sugar from your blood into your cells.

When your body becomes resistant to insulin, your pancreas may produce more insulin to keep blood sugar normal.

This means your blood sugar may look okay for a while, but your insulin may already be working too hard.

That is one reason insulin resistance can hide.

You may have normal glucose or HbA1c at first, while your body is producing extra insulin in the background.

Fasting insulin can help give more information about metabolic health, especially when someone has signs of insulin resistance.

Signs can include:

Belly fat
Strong sugar cravings
Energy crashes after meals
Prediabetes risk
Fatty liver
High triglycerides
PCOS
Family history of type 2 diabetes

This test is not needed for everyone. But if you have metabolic risk factors, it is worth asking your doctor whether it would be useful for you.

The goal is not to scare yourself with numbers. The goal is to understand whether your body is working too hard to keep blood sugar stable.

Cholesterol Panel, ApoB, and Lp(a)

A standard cholesterol test usually checks total cholesterol, LDL, HDL, and triglycerides.

LDL is often called “bad cholesterol” because higher levels can increase the risk of plaque building up in arteries.

HDL is often called “good cholesterol” because it helps carry cholesterol away from the blood.

Triglycerides are fats in the blood. High triglycerides can link with insulin resistance, fatty liver, diabetes risk, and heart health problems.

But standard cholesterol does not always tell the full story.

Two other tests worth knowing are ApoB and Lp(a).

ApoB helps show the number of cholesterol-carrying particles that can contribute to artery plaque.

Think of cholesterol like traffic on the road. LDL cholesterol tells you how much load is being carried. ApoB helps count how many risky vehicles are on the road.

Sometimes the number of particles matters because more particles can mean more chances for them to enter artery walls.

Lp(a), pronounced L P little a, is another important marker.

Lp(a) is mostly genetic. That means your family background plays a large role.

A standard cholesterol test does not usually include Lp(a). You need a specific blood test to know your level.

This is important if heart disease, stroke, or heart attack runs in your family, especially if it happened at a younger age.

You can eat well, look slim, exercise, and still have high Lp(a), because lifestyle does not fully control it.

That does not mean you should panic. It means you should know your risk and speak to your doctor about the best way to protect your heart.

Ask about a cholesterol panel, ApoB, and Lp(a) if you have:

Family history of early heart disease
High blood pressure
Diabetes or prediabetes
High triglycerides
Belly fat
Previous abnormal cholesterol result
Chest pain or heart symptoms
A history of stroke or heart disease in the family

Heart risk is not only about how you look on the outside. Blood markers can reveal what the eyes cannot see.

Kidney Function Test and Urine ACR

Your kidneys filter waste from your blood.

They also help balance fluid, manage minerals, support blood pressure control, and remove extra waste from the body.

Kidney problems can develop quietly. In the early stages, many people do not feel pain.

Common kidney blood tests include creatinine and eGFR.

Creatinine is a waste product from muscles. Your kidneys remove it from your blood.

If creatinine rises, it may suggest your kidneys are not filtering as well as expected.

eGFR estimates how well your kidneys are filtering blood.

But kidney testing should not only stop with blood.

Urine ACR is also important.

ACR means albumin-creatinine ratio. It checks whether small amounts of protein are leaking into your urine.

Protein in urine can be an early sign of kidney damage, especially in people with diabetes or high blood pressure.

This matters because high blood pressure and kidney problems often affect each other.

High blood pressure can damage the kidneys.

Kidney problems can raise blood pressure.

If both are ignored, they can create a cycle that becomes harder to manage later.

Ask about kidney function testing and urine ACR if you have:

High blood pressure
Diabetes
Family history of kidney disease
Foamy urine
Swollen ankles or legs
Long-term use of some painkillers
Heart disease
Abnormal previous kidney results

Your kidneys may not give obvious symptoms early, so testing can help catch warning signs sooner.

Liver Function Test and GGT

Your liver works like a busy processing centre.

It helps process nutrients, handle alcohol, store energy, support digestion, and clear waste from the body.

Liver function tests often include ALT, AST, ALP, bilirubin, albumin, and sometimes GGT.

ALT and AST can rise when liver cells are irritated or damaged.

ALP and bilirubin can help show issues with bile flow or liver processing.

Albumin can help show how well the liver is making certain proteins.

GGT can rise with alcohol-related liver stress, bile duct problems, fatty liver, and other liver strain.

Many people think liver problems only happen to people who drink alcohol heavily.

That is not true.

Fatty liver can also link with insulin resistance, belly fat, high triglycerides, type 2 diabetes risk, and diets high in refined carbohydrates or sugary drinks.

The difficult part is that liver problems may not show strong symptoms at first.

You may feel fine while liver enzymes are already rising.

Some people may feel tired, bloated, heavy after meals, or notice discomfort in the upper right side of the belly. Others may have no symptoms at all.

Ask about liver function testing if you have:

Belly fat
High triglycerides
Diabetes or prediabetes
Regular alcohol intake
Unexplained tiredness
Yellow eyes or skin
Dark urine
Pain or discomfort in the upper right abdomen
Previous abnormal liver result

A liver test does not diagnose everything by itself, but it gives useful clues.

Thyroid, Ferritin, B12, Folate, and Vitamin D

This final group matters because many people feel tired for years without knowing why.

They sleep more, drink coffee, try supplements, and blame stress. But sometimes tiredness comes from thyroid issues or low nutrient levels.

Thyroid tests usually start with TSH. Sometimes doctors also check free T4, depending on symptoms and the first result.

Your thyroid helps control body speed, energy, temperature, mood, digestion, and weight.

If your thyroid is underactive, you may feel tired, cold, low in mood, constipated, dry-skinned, or gain weight more easily.

If your thyroid is overactive, you may feel shaky, anxious, sweaty, lose weight unexpectedly, or notice a fast heartbeat.

Ferritin checks your iron stores.

This is important because your haemoglobin can still look normal while your iron stores are already low.

Low ferritin can link with tiredness, dizziness, weakness, breathlessness, poor exercise tolerance, restless legs, and hair shedding.

Vitamin B12 supports nerves and blood cells.

Low B12 can cause tiredness, tingling, numbness, memory issues, low mood, balance problems, and mouth ulcers.

Folate also supports blood cells and cell growth.

Vitamin D supports bones, muscles, and immune function. Low vitamin D is common in places with less sunlight, and people with darker skin may be at higher risk of low levels.

Ask about these tests if you have:

Constant tiredness
Low mood
Brain fog
Hair shedding
Dizziness
Tingling or numbness
Restless legs
Weakness
Heavy periods
Vegan or vegetarian diet
Gut issues
Long-term metformin use
Long-term acid reflux medication use
Low sunlight exposure

Do not guess with supplements if you can test first.

Too much iron can be harmful.

Too much vitamin D can also cause problems.

Testing gives direction. Guessing can cause confusion.

How Often Should You Get Blood Tests?

There is no one answer for everyone.

Your testing schedule depends on your age, symptoms, family history, existing health conditions, medication, weight, blood pressure, and previous results.

Some people may need checks once a year.

Some may need them more often.

Some may only need certain tests once, such as Lp(a), unless their doctor says otherwise.

The best step is to speak with your GP or healthcare professional and ask what makes sense for your situation.

How to Understand Your Results

When you get your results, don’t panic over one number.

A result slightly outside the normal range does not always mean something serious.

Your doctor will look at the full picture.

They may consider:

Your symptoms
Your age
Your medication
Your family history
Whether you were fasting
Recent illness or infection
Your previous results
Whether the test needs repeating

Trends matter.

One result is a snapshot. Several results over time tell a better story.

If your HbA1c is rising year after year, that matters.

If your eGFR is dropping over time, that matters.

If your liver enzymes keep rising, that matters.

If your ferritin keeps falling, that matters.

Keep copies of your blood test results when possible. They help you and your doctor see what is changing.

Final Thoughts

Blood tests are not there to frighten you.

They are there to give clues.

A full blood count can show blood cell problems.

HbA1c can show long-term blood sugar control.

Fasting insulin can give clues about insulin resistance.

Cholesterol, ApoB, and Lp(a) can help explain heart risk.

Kidney function and urine ACR can reveal kidney stress.

Liver function and GGT can show liver strain.

Thyroid, ferritin, B12, folate, and vitamin D can help explain tiredness and hidden deficiencies.

You should not diagnose yourself from one result.

Use your results as a starting point for a proper conversation with a qualified healthcare professional.

Your body may warn you before serious symptoms appear. Blood tests are one way to listen early.

Disclaimer: This article is for educational purposes only and is not medical advice. Speak to a qualified healthcare professional before making health decisions or changing your treatment.