All You Should Know About Fasting Before Your Blood Test

Blood test helps in the diagnosis of different ailments. Some blood tests require special preparation before drawing your blood sample while others do not. Before you get some blood tests, you may need to fast before test. If this is the case, the doctor may instruct you when you should take your last meal before the test. Your doctor may tell you to drink only water for a specific number of hours leading to your private blood test in London.

Getting some tests while fasting gives a more accurate result. Taking foods or drinks before tests that require fasting supplies your body proteins, fats, carbohydrate, and minerals which impact negatively on your test result.

Only some blood tests require fasting, and they include

• Renal function panel
• Liver function test
• Blood glucose test
• Cholesterol test
• Basic metabolic panel
• Lipoprotein panel
• Triglyceride level test
• Low-density lipoprotein (LDL) level test
• High-density lipoprotein (HDL) level test

If you need blood work done and your doctor does not tell you whether or not you should come for the test fasting, ensure you ask the doctor about it.

Some tests like fecal occult blood tests do not require fasting, but avoiding certain foods like broccoli, red meat, and some medications could give a false-positive result. Make sure you always ask your doctor for advice to prepare for your test.

How long should I fast before my blood test?

The duration of your fasting depends on the test you want to perform. Most tests require you to not eat or drink anything except water for at least eight hours before the test. Some others may need you to fast for about 12 hours before the test.

• Tips to follow

Schedule the appointment for your test early in the morning. Your sleeping hours can also serve as fasting time, but do not eat or take coffee when you wake up.

Can I take a coffee while fasting for a test?

Taking coffee either black or with sugar and milk will interfere with your test result because the soluble plant component and caffeine in the coffee affects your blood composition.

Caffeine is a diuretic, and it increases the frequency of urination. This causes dehydration making it more difficult for your health professional to find a vein for the collection of your blood sample, and this makes the blood collection process more stressful and difficult.

Can I take alcohol if I am fasting for a blood test?

Blood tests like triglyceride tests and liver function tests may require you not to take alcohol 24 hours before your test because trace amounts of alcohol may be found in your bloodstream days after consuming the alcohol. This may interfere with your test result. If you have issues with alcohol consumption, talk to your doctor about it.

You should also ask your doctor if you can smoke before your blood test and if smoking will interfere with your blood test result.

Can I drink water before my blood test?

You can drink water before your blood test except your doctor instructs you otherwise. Getting a blood test is different from some surgical procedures which require you not to take anything because you need to be on an empty stomach.

Plain water before a blood test is allowed, so try to leave out the lemon or any other fruit you squeeze into your water. Do not take carbonated or flavored beverages. Drinks like club soda and Seltzer are also off-limits.

• Tip to follow

Drinking lots of water hydrates you and makes your veins more visible and plumper. Ensure you remain hydrated at least two days before your test and endeavor to drink lots of water before the nurse draws your blood, as this makes the blood collection process easier.

What to do if my child needs to fast for a blood test?

Children may also need to fast before some tests, like adults. If your child needs to carry out a test that requires fasting, the pediatrician will inform you how long your child should fast.

Tips to follow

• Schedule the appointment for the test as early as possible in the morning
• Try to distract your child hours before the test. You could let the child play games with a phone or watch cartoons on the television.
• Keep a snack handy for the child to eat after the test.
• If your child eats before the test, it may be best to reschedule, so the test doesn’t give an inaccurate reading.

If I am pregnant, can I fast for a blood test?

If you are pregnant, you would need a lot of blood tests to help in the assessment of your health and that of the baby during and after the pregnancy. Some of the tests required during pregnancy call for fasting and your doctor will let you know when you need to fast for a blood test.

Fasting during pregnancy is safe if you are healthy, and your pregnancy is not a high-risk one. You may need to drink lots of water or stay indoors, especially if the weather is hot.

Some pregnant women experience heartburn during fasting. While waiting for the collection of your blood sample, and you feel any discomfort or symptom that gives you concern, inform your doctor.

If the doctor who ordered the test is not your obstetrician/gynecologist, inform the doctor about your pregnancy.

If you need a private blood testing in London that requires fasting, visit Blood London today or contact us on 020 71830244 to book an appointment for the test.

Frequently asked question

What would happen if you do not fast for a blood test?

If you fail to fast before a blood test that requires fasting, the result of your test would be inaccurate. If you forget about your test and go-ahead to either drink or eat anything, you may need to call your healthcare provider to find out if you can still get the test done.

Analysis of some tests may be possible with another notation asides fasting. If you had anything, either a cup of coffee or a complete breakfast, tell the medical professional drawing the blood. They may be able to perform the test but put into consideration the meal, to arrive at the right result. If fasting is a must for the test, you may have to reschedule.