How long does it take to test fasting blood sugar?

Do I need to fast before taking blood? How long is an appropriate fasting period? Can I drink water before the examination? Today we will answer them one by one for you.

Why do you need to fast for blood tests?

If a "sugar patient" eats something before blood collection, the biochemical components in the blood will change, and the measured results may be biased when compared with normal values, or even cause "misjudgment."

This is mainly because after food enters the human body, it will decompose into small molecular substances and enter the blood, and the serum concentration will increase accordingly, thus causing interference to the test results. For example, after drinking alcohol for several hours, blood lactate, blood uric acid and other test results will be higher than in the fasting state; after eating high-fat food, the test results of triglycerides can increase several times; eating high-sugar food can increase blood sugar within two hours. rise rapidly. Therefore, many laboratory tests require “diabetes patients” to fast before drawing blood.

Can I drink water before taking blood?

Under normal circumstances, it is recommended that "sugar patients" do not drink water or drink less water before blood drawing, but they can drink water when they are very thirsty. You can drink a small amount of water on the morning of the blood draw and the night before. You can drink a few sips of water each time (50-100 ml), as long as you don’t drink a lot of water (<200 ml), because drinking a lot of water will cause blood dilution and affect the test results. = Generally, it will not affect the test results. In addition, if you wait too long while queuing up for registration or examination at the hospital, you can also drink a small amount of water. This can not only quench your thirst, but also avoid the effects of blood concentration caused by lack of water. Test results.

How long is the appropriate time to fast before the examination?

When we usually talk about fasting, many "sugar friends" understand it as skipping breakfast. In fact, fasting before the test means maintaining a normal diet the day before the blood draw, eating a light dinner, not drinking alcohol, strong tea, coffee and other irritating drinks, and no fasting after 20:00 in the evening (no later than 22:00) Eat again, do not drink water or drink less water, skip breakfast, do not exercise after getting up the next day, and then calmly go to the hospital for examination.

The best fasting time for "sugar friends" examination is 12 to 14 hours, and at least 8 hours of fasting should be ensured. Because in this state, various substances in the body of "sugar lovers" are relatively stable and balanced, avoiding the impact of dietary factors and physiological activities during the day on the test results (or in other words, the impact is very small), which makes it easier for doctors to compare the test results with normal reference values. Make a comparison. Fasting time that is too long or too short may affect the test results. If a "diabetic" fasts for too long, collecting blood in a hungry state may reduce some measured values. For example, being hungry for too long may easily lead to hypoglycemia and severe complications. Patients may even experience fainting and shock. In addition, if you are hungry for too long, the sensitive blood sugar regulation mechanism will mobilize the glycogen stored in the body for the body to consume, so the blood sugar level will be higher than usual, which may also lead to misdiagnosis and mistreatment.

Which items require fasting and which items do not require fasting?

Since many laboratory tests require subjects to fast, many "diabetics" believe that all laboratory tests require fasting. In addition, many of our medical staff will tell patients to fast for all laboratory tests when they are confused. In fact, this is not the case. Some examination items are strict and the patient must fast; while some examination items are not strict or do not require fasting, so the patient can relax a little.

1. Items with strict fasting requirements (absolute fasting): fasting blood sugar, blood lipids, kidney function, liver function (especially enzymes), electrolytes, etc.

2. Items with less strict fasting requirements (you can eat some food, but not high-protein and high-fat foods): blood routine, erythrocyte sedimentation rate, coagulation function, tumor markers, autoantibodies, rheumatoid factor determination, myocardial markers, thyroid Function etc.

3. Items with special requirements: You must abstain from meat for three days before doing the endogenous creatinine clearance test, and you must not drink coffee and tea; avoid high-fat diet three days before the blood lipid test; postprandial items (glucose tolerance test, C - Peptide and insulin release test) You need to strictly follow the requirements and take blood at the right time after taking sugar (if there are too many people queuing up for blood drawing, please contact the staff in advance to ensure that blood can be collected on time).

4. Items that do not require fasting: emergency patients (severe coma or emergency cases) can collect blood at any time, such as blood sugar, electrolytes, blood gas analysis, amylase, myocardial markers, renal function, etc.; glycated hemoglobin is not affected by diet and does not require fasting; other viruses Medical testing does not require fasting blood, such as HIV and syphilis testing.

Of course, if you are unclear about which items require fasting and which do not require fasting, try your best to do the fasting test if conditions permit. In addition, in addition to laboratory examinations, X-ray gastrointestinal angiography, gastroscopy and gallbladder B-ultrasound examination also require fasting. Please consult doctors in relevant departments for these matters.