Preparing for your test

Prepare well. Get the clearest possible results.

Food, hydration, exercise, supplements and the time of your appointment can influence some biomarkers. This simple guide helps you arrive ready for your PER blood test.

See the checklist Find a blood-draw location
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Your personal instructions come first. Your booking confirmation is specific to your panel. Follow it if it differs from this general guide, and contact us before your appointment if anything is unclear.

8–12 hours
Water-only fast when instructed
48 hours
Avoid strenuous exercise
Stay hydrated
Drink plain water before attending
Keep medication safe
Never stop prescribed medicine without advice

Your preparation timeline

What to do before your appointment.

Use this as your general checklist alongside the instructions sent for your specific test.

  1. 48 hours before

    Keep your routine steady

    • Avoid strenuous exercise and unusually intense training.
    • Unless medically prescribed, pause supplements for 48 hours when your test instructions ask you to.
    • Do not stop prescribed supplements or medication without advice from the clinician responsible for them.

  2. The night before

    Begin fasting if required

    • Most comprehensive PER blood panels require an 8–12 hour water-only fast.
    • Do not fast for longer than instructed.
    • Choose a morning appointment where possible, especially when testosterone is being measured.

  3. Test morning

    Drink plain water

    • Stay well hydrated to support an easier blood draw.
    • During a fast, have water only: no tea, coffee, milk, juice, sweets or chewing gum.
    • Avoid smoking for at least 30 minutes before your appointment.

  4. At the clinic

    Share anything relevant

    • Bring your booking details and any identification requested.
    • Tell the collection team if you are prone to fainting or have difficult veins.
    • Make sure your PER practitioner has an up-to-date list of medication and supplements.

Fasting explained

Water only means water only.

Eating or drinking anything other than plain water can alter glucose, insulin, lipids, iron and some hormone measurements. Consistent preparation also makes follow-up results easier to compare.

During your fasting window

  • Do drink plain water. Good hydration can make sample collection easier.
  • Do not have food or calorific drinks. Avoid tea, coffee, milk, juice, alcohol, sweets and chewing gum.
  • Do not extend the fast. Longer fasting is not better and may make you feel unwell.
  • If fasting is unsafe for you, contact us. This is especially important if you have diabetes, are pregnant, have a history of fainting or must take medication with food.

Medication and supplements

Protect your health first.

  1. 01

    Prescribed medication

    Continue it as prescribed unless the clinician responsible for that medicine has specifically told you otherwise. If it must be taken with food, contact us before attempting a fast.

  2. 02

    Biotin and supplements

    Biotin, often found in hair, skin and nail products or multivitamins, can interfere with laboratory tests. We recommend stopping non-prescribed supplementation at least 48 hours beforehand; prescribed products require clinical advice.

  3. 03

    Tell us what you take

    Provide an accurate list of medication, hormones, vitamins, minerals and other supplements. These details can be important when your results are interpreted.

Test-specific timing

Some results depend on when you test.

Your PER team will confirm whether timing matters for your panel. Do not change medication, contraception or hormone therapy solely for a blood test unless advised by the appropriate clinician.

Not feeling well?

An acute illness, infection, recent surgery or major change in medication can influence results. Contact the PER team before attending so we can advise whether the appointment should go ahead.

Female hormones

Where cycle-day hormone assessment is relevant, testing is commonly recommended on days 2–5 after the start of the period, ideally day 3. Post-menopausal clients or those having a general check may be tested on another day. Hormonal contraception and hormone therapy can affect interpretation.

Male testosterone

A morning appointment is preferred when testosterone is being assessed because levels naturally vary through the day.

Urine or stool samples

If your panel includes a urine or at-home stool sample, follow the separate collection-kit instructions. Collection timing, storage and return requirements may differ from the blood test.

PER Multi-System Health Panel

For this test, we recommend an 8-hour water-only fast, no strenuous exercise for 48 hours, no smoking for at least 30 minutes and pausing non-prescribed supplements for at least 48 hours. Follow the final instructions supplied with your booking.

After your blood draw

Take a moment before you leave.

Most people can continue their day normally after a routine blood draw.

  • Apply firm pressure to the site for as long as the collector advises.
  • Eat and rehydrate after a fasting test.
  • Avoid heavy lifting with that arm if the site remains tender.
  • Mild bruising can occur; seek medical advice for persistent bleeding, worsening pain, marked swelling, redness or other concerning symptoms.

Unsure about any instruction? Contact the PER team before your appointment.

Ready for your appointment?

Find your blood draw location.

Choose from 53 professional blood-draw locations across the UK, or speak to us about a mobile collection where needed.

View blood draw locations Ask the PER team