Preparing for your blood test

Please review the preparation and timing guidance below before attending your appointment.

Preparing for a blood test

Please review the preparation and timing guidance below before attending your appointment.

Not all blood tests require fasting. Whether you attend fasted should be decided by you or the healthcare professional requesting your test.

Eating and drinking before your appointment can temporarily affect certain analytes, particularly glucose, insulin and triglycerides. This may influence the result or how it is interpreted. Other analytes within a profile may also have specific preparation requirements.

Some hormones, including cortisol and testosterone, naturally fluctuate throughout the day. A morning appointment or a specific collection time may therefore be recommended. Following the timing guidance for your chosen test helps provide the most useful and comparable result.

If you decide, or have been advised, to fast:

Fast for 8–10 hours before your appointment.
Drink plain water only.
Avoid tea, coffee, juice and flavoured drinks.
Do not chew gum, smoke or undertake strenuous exercise during the fasting period.
Continue prescribed medication unless a healthcare professional has advised otherwise.

If you are repeating a test, following similar preparation and collection timing each time may make the results easier to compare.

Where we speak with you before your appointment, we will ask about your health and your reasons for testing, and can discuss whether any preparation is relevant to you.

Before you consider fasting — please read

Do not fast if it may be unsafe for you. This includes if you have diabetes, take insulin or medicines that lower blood sugar, are pregnant or breastfeeding, are prone to low blood sugar, are frail or unwell, have poor nutritional intake or a history of an eating disorder, or if the test is for a child or young person.

If any of these apply, please do not fast. Contact support@easytests.co.uk before your appointment and we will advise you.

Never stop, delay or change prescribed medicines unless a healthcare professional has specifically told you to.

Do’s and don’ts

🟢 DO
• Check your test or profile preparation and timing.
• Follow advice from the healthcare professional requesting your test.
• If fasting, fast for 8–10 hours and drink plain water only.
• Keep repeat-test preparation and timing consistent.
• Seek advice before fasting if you have diabetes, are pregnant or breastfeeding, or are concerned about fasting safely.

🔴 DON’T
• Don’t assume every blood test requires fasting.
• While fasting, avoid tea, coffee, juice, flavoured drinks, gum, smoking and strenuous exercise.
• Don’t stop prescribed medication unless professionally advised.
• Don’t ignore test-specific timing guidance, including morning collection where recommended for hormones.

At your appointment

Before you arrive

Please arrive 10 minutes before your appointment.

You will receive a consent form by email to complete in advance. Some clinics also allow you to complete it when you arrive.

Bring photo ID and details of any prescribed medication.

If you feel anxious

If you are worried about needles or have previously felt faint during a blood test, tell the person taking your sample. They can help you feel more comfortable and, if needed, take the sample while you are lying down.

Test-specific requirements

Some tests may require health measurements, a urine sample, a pre-medical lifestyle questionnaire review or additional information. Follow the instructions provided for your chosen test. Please ask any questions during your appointment, confirm your preferred contact method and tell us about any worries so we can support you.

If you attend a partner collection site

Some appointments take place at partner collection Randox Health centres rather than at our Crewe clinic. If staff at a collection site give you preparation advice that differs from ours, please contact us before your appointment rather than acting on it.

Which results can be affected by food

If these markers matter to your reasons for testing, attending after a period without food — plain water only — gives results that are easier to interpret and easier to compare if you test again later.

Glucose (blood sugar) - Rises after eating. A fasting glucose result is the one used for standard metabolic interpretation.
Insulin - Rises with food. Baseline interpretation assumes a fasted sample.
C-peptide - Released alongside insulin, so it follows the same pattern.
Leptin - Levels shift with recent food intake.
Adiponectin and resistin - Used in metabolic assessment, where consistent conditions matter.
Homocysteine - Affected by recent meals; a longer period without food is usually preferred.
Gastrin and gut hormones - Require a fasted sample. Acid-suppressing medicines can also affect results — do not stop them without clinical advice.
Triglycerides - Rise after a meal. Total cholesterol, LDL and HDL are far less affected.

Which results are NOT affected by food

You do not need to go without food for any of the following:

HbA1c - Reflects average blood sugar over about three months. Can be taken at any time.
Cholesterol, LDL, HDL - A routine lipid profile does not need to be fasted for standard cardiovascular assessment.
Apolipoproteins and Lp(a) - No routine fasting requirement.
Full blood count - No routine fasting requirement.
Kidney function and electrolytes - No routine fasting requirement.
Liver function tests - No routine fasting requirement.
CRP, ESR and inflammation markers - No routine fasting requirement.
Ferritin, B12, folate, vitamin D - No routine fasting requirement.
Thyroid tests (TSH, FT4, FT3) - No fasting needed. High-dose biotin supplements can interfere with some assays.
Tumour markers (CA125, CEA and similar) - No fasting needed. PSA has separate preparation — see section 6.
Antibody and immunology tests - No routine fasting requirement.

Which results are affected by the time of day

Several hormones follow a natural daily rhythm. A result taken late in the day can look low simply because of when the sample was collected, rather than because anything is wrong. Where these markers matter to you, a morning appointment — ideally between 8am and 11am — gives the most interpretable result.

Testosterone - Morning, ideally 8am to 11am. Levels are highest in the morning and fall through the day. A low afternoon result may not reflect your true level.
Cortisol - Around 9am for a routine measurement, unless a specific timed test has been requested.
Prolactin - At least an hour after waking and before eating. Stress, strenuous exercise and breast stimulation beforehand can raise it.
SHBG and free androgen index - Morning, where used alongside testosterone.
FSH, LH, oestradiol, progesterone - Timing within the menstrual cycle can matter more than time of day, depending on what is being assessed.
DHEA sulphate, androstenedione - Morning is preferred for consistency.
Parathyroid hormone (PTH) - Mid-morning is preferred for consistency.

If you are monitoring treatment over time — for example testosterone therapy — the most important thing is consistency. Try to book at a similar time of day each time, so results can be compared properly.

Other Tests Preparation....

Any test including a urine sample - Please arrive able to provide a sample and avoid emptying your bladder immediately before your appointment. Do not deliberately drink excessive amounts of water.
Urine albumin:creatinine ratio (ACR) - A first-morning sample is preferred. Avoid drinking large amounts of fluid beforehand, as a very dilute sample may be unsuitable.
Creatine kinase (CK), LDH, muscle markers - Avoid heavy or unaccustomed exercise beforehand where possible, as exertion raises these.
Thyroid and prolactin tests - High-dose biotin supplements can interfere with some assays. Mention any supplements you take.
H. pylori stool antigen - Acid-suppressing medicines can affect the result. Do not stop prescribed medication without clinical advice.
Coeliac screening - Do not cut gluten out of your diet before testing unless a clinician has told you to, as this can make the test unreliable.

Receiving your results

Most results are sent by email within three working days, although turnaround times vary by test. Some tests require longer for laboratory analysis and clinical interpretation, and certain DNA tests may take up to three months.

Please check the expected turnaround time for your chosen test before booking.

If a result is above or below a critical threshold and requires urgent attention, our healthcare support worker will contact you by phone or email.

If you need a private GP or specialist referral following your result, please contact us so we can explain the available support.

If you are unwell

If you are unwell or have symptoms needing urgent attention, contact your GP, call 111 or attend A&E. Do not wait for test results.

Preparing for your PSA test

For 48 hours before your test, please avoid ejaculation, anal sex, cycling and strenuous exercise, as these activities may temporarily increase your PSA level.

If you currently have a urine infection, or have recently recovered from one, please contact us before booking. Testing will usually need to wait for 4–6 weeks after the infection has cleared.

Please also tell us if you have recently had a prostate examination, biopsy, procedure or urinary catheter.

You may eat and drink normally unless you are having another test that requires fasting.