Laboratory preparation

How do I prepare for my laboratory tests?

Some laboratory results can only be used if you have prepared properly. The essentials for the morning of your blood test are right here; the details follow further down.

Fasting

Many blood tests have to meet certain conditions to be meaningful. For analyses such as blood lipids, sugar, acid–base balance or dark-field microscopy, you must come ‘fasting’.

What does fasting mean?

• Solid food may only be eaten until midnight the day before.
• After that, drink according to your thirst. You should not arrive ‘dehydrated’, but do not overdo it either.
• Only water is allowed, at body temperature.
• No coffee and no black or green tea, as both contain caffeine. Sweetened drinks and sweeteners are not allowed either, especially before the glucose tolerance test and the insulin test.

Medication and supplements

• Only take essential medicines before the blood test; take the others afterwards. You can bring them with you for this.
• If you are unsure which medicines you may take in the morning, please ask us.
• Supplements should be stopped at least 3 days before the laboratory appointment, especially those containing biotin.

Biotin

Taking a supplement that contains biotin is a critical piece of information, because it directly affects the accuracy of your results.

Biotin (vitamin B7) is widely used in laboratory ‘sandwich’ and ‘competitive’ assays to measure blood markers. When there is excess biotin in your bloodstream, it chemically interferes with the measurement. The exact direction of the error depends on the laboratory equipment used.

Thyroid

For thyroid values to be measured correctly, the supplement biotin must be stopped 3 days before the blood test, because biotin is also used in measuring the hormones.

Bone markers

Biotin also distorts the markers of bone turnover. For the standard assays:

• CTX (bone breakdown): High-dose biotin typically causes a falsely low result. Your true rate of bone breakdown may therefore be higher than measured.
• P1NP (bone building): Biotin can cause a falsely low result here as well. Your actual bone-building activity may therefore be higher than measured.

For this reason, please also stop taking biotin 3 days before the blood test when bone markers are to be measured.

Preparing for a hormone blood test

Correct preparation is crucial for a meaningful hormone measurement.

Hormone creams, gels or solutions (e.g. with oestradiol, progesterone or testosterone) must not be applied to the crook of the elbow or the forearms, as this can lead to falsely raised laboratory values.

Please therefore note:

• On the day of the blood test, do not apply hormone preparations to your arms or near the puncture site
• Ideally, the last application should be at least 24 hours before the blood test
• Alternatively: apply to parts of the body that are not used for taking blood (e.g. the thighs)
• If possible, the blood should be taken before the next application

Even if the skin is cleaned carefully, residues can remain and distort the measurement.

If you are unsure, please speak to us before the blood test.

Further notes

Sport

• Avoid morning exercises and all strenuous activity.
• And do not cycle to the practice.

This applies in particular to blood sugar, liver, blood lipid and muscle values, uric acid and urea, lactate and EPOC (acid–base analysis), hormones and stimulation tests such as the glucose tolerance test (OGTT).

Smoking

Tobacco or other nicotine products should also not be used after midnight.

Urine sample

If a urine sample is also planned, please come with some urine in your bladder.

Illness

If you have a cold or another acute illness unrelated to the condition being investigated, it is advisable to postpone the blood test until the symptoms have completely gone.

Saliva sampling

For some tests, you collect saliva samples yourself. We give you Salivettes for this: small tubes containing a cotton roll. Follow these steps from our partner laboratory’s instructions.

Saliva is collected on an empty stomach: do not eat or drink anything before or while you collect the samples. Have breakfast only once you have collected all of them.

Please also note:

• The saliva samples must not contain any blood, for example from bleeding gums or a wound in the mouth.
• Do not use mouthwash or any similar rinse.
• Take the saliva samples before brushing your teeth.
• Do not smoke while you are collecting saliva.

1. Before you start, rinse your mouth with water and spit all of the water out again. Only begin collecting once your saliva flow has returned to normal.
2. Open the cap of the Salivette and take the cotton roll out of the insert.
3. Place the cotton roll in one cheek for 2 minutes, chew on it gently and soak it thoroughly with saliva.
4. Put the cotton roll back into the insert and close the Salivette carefully.
5. Label the Salivette with your name and the date and time of sampling.
6. Repeat steps 2 to 5 for each further saliva sample.

Storage and transport

• Keep the saliva samples in the refrigerator until they are sent.
• Put the Salivettes into the addressed envelope and send them to the laboratory, or hand them in at the practice.

laborteam instructions as a PDF (in German)

The OsteoTest

What the test measures

The OsteoTest determines whether bone metabolism is mainly building up or breaking down bone. To do this, the calcium isotope composition is measured in the blood samples.

There are still few long-term data on this analysis. For this reason, classic markers such as CTX or procollagen (P1NP) usually have to be used as well.

During treatment, the OsteoTest is used to check whether a measure improves bone metabolism.

Procedure

The blood must be taken in the morning, fasting. In addition, any sporting activity before the test is prohibited.

Important: After the blood test you must complete an online form (in German). Without this information, the results will not be released.

Where it says ‘Barcode’, enter the number (letters and digits) shown on the tube. Please pay attention to upper and lower case. We will give you this tube when your blood is taken.

To the online form

The result is available after about one week.

What do my values mean?

Don't panic about the red numbers! Laboratory results have to be looked at individually. Don't let the colours mislead you.

To the page ‘What do my values mean?’ (in German)