A genotype blood test is a laboratory analysis that tells you which pair of haemoglobin genes you inherited — most commonly reported as AA, AS, AC, SS, SC or CC. In the UK, most people search for one of these tests for a very specific reason: couples thinking about children who want to check compatibility, adults with West African, African-Caribbean, Mediterranean, Middle Eastern or South Asian heritage who were never screened as newborns, and people whose GP has flagged something in a routine full blood count. This guide walks through what a genotype is, how the test works, what the letters mean, and where you can get tested privately if you don’t want to wait.

What is a genotype?

In everyday UK health conversations, “genotype” almost always refers to your haemoglobin genotype — the pair of genes you inherited that determine the type of haemoglobin your red blood cells produce. Haemoglobin is the protein that carries oxygen from your lungs to the rest of your body. Small changes in the genes that code for it can change how well your red blood cells work.

The two most clinically important variants are:

• HbS, the sickle gene, which can cause red blood cells to distort into a rigid crescent shape under certain conditions.
• HbC, another haemoglobin variant that is generally milder than HbS but still relevant, particularly if inherited alongside it.

Everyone inherits one haemoglobin gene from each parent. The pair you end up with is your genotype.

Genotype is not the same as blood group

A common source of confusion. Your blood group (A, B, AB or O, positive or negative) is about the antigens on the surface of your red blood cells and matters mainly for transfusions and pregnancy. Your genotype, in this context, is about the type of haemoglobin inside those cells. The two are inherited separately and one tells you nothing about the other.

What is a genotype blood test?

A genotype blood test is a laboratory analysis of a small venous blood sample that identifies which haemoglobin variants you carry. In UK private and NHS labs, the underlying method is usually:

• Haemoglobin electrophoresis, which separates different haemoglobin types using an electric current, or
• High-performance liquid chromatography (HPLC), which separates them by chemistry, or
• A combination, sometimes with isoelectric focusing or DNA analysis for unclear results.

You may see this listed on request forms as “haemoglobinopathy screen”, “Hb electrophoresis”, “sickle cell screen” or simply “genotype test”. They overlap substantially. If you are trying to check compatibility with a partner before starting a family, ask specifically for a haemoglobinopathy screen rather than a bare sickle cell solubility test — the solubility test detects HbS but does not distinguish AS from SS, and misses HbC entirely.

How do I know my genotype? Three routes in the UK

You have three practical options.

1. Look at your existing records. If you were born in the UK from around 2006 onwards, you were almost certainly screened for sickle cell as a newborn as part of the NHS Sickle Cell and Thalassaemia Screening Programme. If you have been pregnant in the UK, you were offered screening in early pregnancy. GP records, red books and hospital antenatal notes are worth checking before you pay for another test.

2. Ask your GP. A GP can request a haemoglobinopathy screen on the NHS if there is a clinical reason — planning a pregnancy, a partner with a known trait, a family history, unexplained anaemia, or belonging to a group where variants are more common. Availability and waiting times vary by area.

3. Book a private genotype blood test. If you want a result on your own timeline, or your GP has declined a referral, a private clinic can arrange the same laboratory test, usually with faster turnaround. This is the route most of Swift Blood Tests’ patients use — see genetic and genotype blood testing for what is included, or browse our full range of blood test services.

The genotype types explained

The letters simply describe which two haemoglobin genes you inherited.

You may also see combinations involving beta-thalassaemia (for example, HbS/β-thalassaemia), which behave similarly to sickle cell disease and are picked up by the same screening test.

If your result is anything other than AA and you did not already know, book an appointment with your GP or a haematologist to discuss what it means for you specifically — a written result is not a substitute for clinical interpretation.

What is genotype compatibility?

“Compatibility” in this context is about the risk of passing sickle cell disease or another haemoglobinopathy to a child. Because each parent passes on one of their two haemoglobin genes at random, the combinations you and a partner produce depend on both of your genotypes.

The simple version:

Two carriers (AS + AS) is the situation genetic counsellors most often talk about, because both partners are usually healthy but each pregnancy carries a one-in-four chance of a child with sickle cell disease and a one-in-two chance of a carrier child. Knowing this before trying for a baby lets couples make informed choices, including prenatal testing options and pre-implantation genetic diagnosis in specialist centres.

None of this is a judgement about who “should” or “shouldn’t” have children together. It is information. What people do with it is entirely personal.

When might you need a genotype test?

Common reasons people book one:

• Family planning. You and your partner want to know your combined risk before conceiving. It’s often taken alongside a broader fertility and pre-conception panel.
• You are pregnant and screening has not yet happened, or you want an earlier result than the NHS timeline in your area allows. See pregnancy blood testing for what’s usually included at this stage.
• A partner has been told they are AS or AC and wants you to be tested so the couple’s risk can be calculated.
• Family history of sickle cell disease or trait. A sibling, parent or child has a known genotype.
• Unexplained anaemia on a full blood count, particularly a microcytic picture, where the GP wants to rule out haemoglobin variants or thalassaemia trait. An anaemia blood test is often the first step here, with the genotype screen following if the pattern suggests it.
• Heritage-based awareness. People with ancestry from sub-Saharan Africa, the Caribbean, the Mediterranean, the Middle East, South Asia or parts of South America simply want to know their status. Carrier rates are higher in these populations, but haemoglobin variants exist worldwide.
• Sport or occupational reasons. Some athletes and armed forces applicants are asked to disclose sickle cell trait because of a small increased risk during extreme exertion at altitude or in heat.

You do not need a specific “reason” to want to know your own genotype. Curiosity is a valid one.

What does the test involve, step by step

A typical private genotype blood test takes about ten minutes at the clinic or, if you are booking a home visit, in your own front room.

1. Booking. You choose a date, time and location that suits you.
2. Check-in and consent. A short conversation with a phlebotomist or nurse to confirm your details and go through what the sample is for.
3. Venous blood draw. A single sample from a vein in your arm, usually into an EDTA (purple-top) tube. Most people describe it as a brief scratch.
4. Labelling and transport. Your sample is labelled, packaged and sent to the analysing laboratory the same working day.
5. Analysis. The lab runs HPLC or electrophoresis. If the pattern is unusual, a second technique may be added.
6. Report. Your result is issued as a written report, typically emailed to you securely.

You do not need to fast for a genotype test, you can take your usual medication, and there is no special preparation required. If you have had a blood transfusion in the last three to four months, mention it at booking — donor blood can confuse the result and the lab may want to wait.

How long do genotype results take?

For a UK private test, most patients receive their result within 3 to 7 working days, sometimes sooner. NHS turnaround varies by trust and reason for testing, and can range from a few days for antenatal screening to several weeks for routine referrals.

Two things can extend the wait:

• Unusual haemoglobin patterns that need confirmatory testing (isoelectric focusing or DNA analysis).
• Sample issues — a clotted sample or a labelling query means the lab has to ask for a repeat.

If you are testing in the context of a current pregnancy, book as early as possible so that any decisions about partner testing or further investigations can be made with time in hand.

Can I check my genotype at home?

Not accurately, and not from a fingerprick. What you can do at home is have the venous blood sample collected at home by a qualified nurse or phlebotomist, and then sent to a laboratory. This is the model Swift Blood Tests uses across Essex, Bromley and surrounding areas — the appointment happens where it suits you, but the analysis still runs in an accredited lab. See the phlebotomy services page for how home and clinic visits are arranged.

Standalone “cheek swab genotype kits” sold online are usually testing something different — often ancestry markers or unrelated genetic variants — and should not be relied on for haemoglobin genotype.

NHS or private — which route is right for you?

There is no single right answer. A rough guide:

• The NHS route makes sense if you are pregnant, have a strong clinical indication your GP recognises, and are comfortable with local waiting times. It is free at the point of use.
• The private route makes sense if you want to test proactively (family planning before pregnancy, general awareness), if you need a faster or more predictable turnaround, if you want a home appointment outside working hours, or if your GP has declined a referral because your case does not meet local NHS criteria.

Many couples use both — one partner tests through the GP, the other privately, so the results arrive at similar times.

If you are weighing up private testing more generally, our practical guide to private blood tests in Essex covers what to expect on cost, timings and quality standards across local providers.

Booking a private genotype blood test in Essex and the South East

Swift Blood Tests offers nurse-led venous sampling for haemoglobin genotype testing across Essex, Bromley, Surrey and surrounding areas, either at a clinic base or at home. Turnaround, pricing and exactly what is included are listed on the genetic and genotype blood testing service page.

If you would prefer to book locally in person, the following areas each have a dedicated page:

• Billericay
• Basildon
• Thurrock
• Maldon
• Chelmsford
• Brentwood
• Bromley

The full locations directory lists every area we cover, or the contact page is the fastest way to speak to someone if you’re not sure which service you need or you want to test alongside a partner.

When to speak to a healthcare professional

A written genotype result answers one specific question — which haemoglobin variants you carry. It does not, on its own, tell you what to do next. Please talk to your GP, a haematologist or an NHS Sickle Cell and Thalassaemia counsellor if:

• Your result is anything other than AA and you were not expecting it.
• Both you and your partner are carriers.
• You are pregnant and either partner has a variant.
• You have symptoms you are worried about, such as episodes of pain, unusual fatigue or shortness of breath.

The NHS Sickle Cell and Thalassaemia Screening Programme also provides free, specialist counselling for anyone identified as a carrier.

Frequently asked questions