Laboratory tests requiring a specific time of day

Medication

On the morning of the test, avoid taking any natural health products or vitamins.

Follow your doctor’s instructions about taking your medication.

In case of drug concentration tests, you should usually not take the medication in question before the test is taken.

Thyroid tests: thyrotropic hormone and T4-V: In thyroxine treatment, the sample is taken before the thyroxine tablets.

Iron test fS-Fe: Stop taking any oral iron medication two days before sampling.

You can check the interfering effect of medication on the measured substance in the Duodecim Terveyskirjasto health information service (in Finnish).

Time of day

Certain laboratory tests should be performed at a specific time of day due to the circadian variation in results.

As a rule, laboratory tests should be carried out in accordance with the normal circadian rhythm. If this is not possible, sampling is recommended according to the person’s daily rhythm, which means that sampling is carried out within a couple hours of waking up.

We recommend that samples are taken between 8 a.m. and 6 p.m.

Laboratory panels requiring a specific time of day

• Thyroid gland panel

• The sample is recommended to be taken between 7 a.m. and 2 p.m.

• Thyroid monitoring panel

• The sample is recommended to be taken between 7 a.m. and 2 p.m.

• Lactose intolerance and coeliac disease panel

• A reliable diagnosis of coeliac disease requires the customer to have a gluten-rich diet for at least 6 weeks before sampling.

• Health test panel

• The sample is recommended to be taken between 8 a.m. and 12 noon.

General tests requiring a specific time of day

• Cortisol (S-Korsol)

• Between 7 a.m. and 9 a.m.

• Iron (fP-Fe, fS-Fe)

• Between 7 a.m. and 9 a.m.

• Testosterone (S-Testo)

• Before 12 noon

• Testosterone, free (S-TestoVL)

• Between 7 a.m. and 12 noon

• Thyrotropin (S-TSH)

• Between 7 a.m. and 2 p.m.

Other tests requiring a specific time of day

• Adrenocorticotropin (P-ACTH)

• Between 8 a.m. and 10 a.m.

• Aldosterone (P-Aldos, fP-Aldos)

• Between 7 a.m. and 10 a.m.

• Androstendione (S-Adioni)

• Between 8 a.m. and 12 noon

• Dehydroepiandrosterone (S-DHEA)

• Between 9 a.m. and 12 noon

• Dehydroepiandrosterone, sulfate (S-DHEAS)

• Between 9 a.m. and 12 noon

• Hydroxyprogesterone (17-) (S-17HPROG)

• Between 8 a.m. and 9 a.m.

• Cortisol, saliva (Sa-Korsol)

• Between 11 p.m. and 12 midnight

• Prolactin (S-PRL)

• Between 10 a.m. and 2 p.m.

• Renin, concentration (fP-Reninm)

• Between 7 a.m. and 10 a.m.

• Thyroxine, free (S -T4V)

• In the morning before medication

• Triiodothyronine, free (S -T3V)

• In the morning before medication