Fasting before a blood test

Which tests require fasting

Most blood tests require no fasting at all. Hb, for example, needs no preparation, and before HbA1c, long-term blood sugar, you do not need to prepare either, even though it concerns sugar.

Fasting glucose is the clearest exception. The analysis is then called fP-Glukos, where the f stands for fastande, fasting. At Enkel, fasting also applies to insulin, and the order always shows when fasting is required.

Blood fats usually need no fasting

Practice has shifted here. Since 2021, the Equalis expert group for clinical chemistry recommends that lipid status, meaning cholesterol, LDL, HDL and triglycerides, can be taken without fasting. If the sample shows triglycerides at 4.0 mmol/L or more, a new sample taken fasting is recommended. Karolinska University Laboratory's instruction for LDL cholesterol states that a fasting sample is recommended but not mandatory.

Patient information can still describe lipid tests as fasting tests, and 1177 writes that the sample is usually taken fasting when more blood fats than cholesterol are measured. Lipid measurements alone can often be taken without fasting. Enkel Health’s current cardiovascular profiles also include fasting glucose and therefore require a 10-hour fast and morning sampling. Follow the exact preparation for your order.

How many hours

Fasting before a blood test usually means ten hours without food. 1177 describes it as not eating or drinking for a set time before the sample, most often ten hours. Karolinska University Laboratory's patient instruction states at least ten hours without food.

In practice: eat a normal dinner, skip breakfast and walk in during the morning. Since there is no appointment to keep, you can pick a morning when ten hours have passed.

Water, coffee and medicines

Water is fine during the fast. Karolinska University Laboratory also allows coffee and tea, as long as they are free of sweetener, cream and milk. If your order says something stricter, the order applies.

If you use medicines, particularly glucose-lowering treatment or medicines requiring food, ask your prescriber how to prepare for fasting. Do not change prescribed treatment without advice. Sit down for a while before the draw; Karolinska specifies at least 15 minutes of seated rest.

If you did not fast

A sample taken after food is read differently. Triglycerides run somewhat higher after a meal on average, and calculated LDL cholesterol on average 0.1 to 0.2 mmol/L lower, according to the material behind the Equalis recommendation. For glucose, the report separates fasting values from other values, and the analysis is named fP-Glukos when taken fasting.

If you forgot the fast, the simplest fix is to eat as usual and walk in another morning instead.

This article is general health information, not medical advice and not an assessment of your values. If you have symptoms or concerns, contact your healthcare provider.