Finger prick blood glucose readings and sensor glucose readings won't always match and in fact are likely to be different. That's because sensor glucose readings come from the interstitial fluid (ISF), a thin layer of fluid that surrounds the cells of the tissues below your skin, not from your blood.
There are plenty of factors that may affect the reading: cleanliness of your hands, test strips, food intake, checking time, stress, medications may all be culprits.
Most of the time glucose travels from your blood vessels into the fluid. So, your blood glucose (BG) meter readings and sensor glucose (SG) readings – let's call them BGs and SGs – will be close but will rarely match exactly. This difference is normal and should be expected.
Although you want to get the best results for each skin prick, when you're new to blood sugar testing it can be confusing to watch those results change throughout the day. “It's helpful to understand that blood sugar changes minute by minute,” says certified diabetes educator Karen A.
Dirty glucose meters, unwashed hands, or damaged test strips can all lead to false test results.
Some researchers believe the natural overnight release of what are called counter-regulatory hormones -- like growth hormones, cortisol, glucagon and epinephrine -- makes your insulin resistance stronger. This will make your blood sugar go up.
Squeezing your finger
When you do that, you are getting some interstitial fluid rather than blood. A study shows that this “may lead to unreliable readings." Gently warming the hands ahead of time can help so you don't have squeeze so hard.
Target blood sugar levels differ for everyone, but generally speaking: if you monitor yourself at home – a normal target is 4-7mmol/l before eating and under 8.5-9mmol/l two hours after a meal. if you're tested every few months – a normal target is below 48mmol/mol (or 6.5% on the older measurement scale)
Skipping breakfast—going without that morning meal can increase blood sugar after both lunch and dinner. Time of day—blood sugar can be harder to control the later it gets. Dawn phenomenon—people have a surge in hormones early in the morning whether they have diabetes or not.
Blood sugar levels may rise due to hormones being released in response to stress. Although this has adaptive significance in a healthy patient, in the long run, it can cause insulin resistance and lead to diabetes.
It does not matter which finger is used for glucose measurements. External pressure may lead to unreliable readings. Many insulin-treated patients have to perform SMBG for a lifetime—some of them every day.
Prick your finger with the lancing device at the sides of the finger as there are less nerve ending here than at the tips or the 'pads'. Recommended finger: the World Health Organisation recommends the middle or ring fingers are used for blood glucose tests (second and third fingers).
Blood sugar testing at home
In most cases, doctors ask people to measure fasting blood sugar immediately upon waking and before they have anything to eat or drink. It may also be appropriate to test blood sugar before eating or 2 hours after a meal, which is when blood sugar returns to normal levels.
Check your blood sugar level with your meter at the same time that blood is drawn for lab tests, being sure to use a fingerstick sample, not blood from the blood draw. Then compare your meter's reading with the lab results. Results that are within 15% of the lab reading are considered accurate.
Fingerstick testing is still the most accurate reflection of sugar levels in the blood stream. It's a good idea to discuss meter selection with your health care provider or diabetes educator.
In general: Less than 100 mg/dL (5.6 mmol/L ) is normal. 100 to 125 mg/dL (5.6 to 6.9 mmol/L ) is diagnosed as prediabetes. 126 mg/dL (7.0 mmol/L ) or higher on two separate tests is diagnosed as diabetes.
Drinking plenty of water helps your kidneys flush out excess sugar. One study found that people who drink more water lower their risk for developing high blood sugar levels. And remember, water is the best. Sugary drinks elevate blood sugar by raising it even more.
Doctors suggest that a normal fasting blood sugar range is between 70–100 mg/dL (3.9–5.6 mmol/L). If your fasting blood sugar is consistently over 126 mg/dL (7 mmol/L), your doctor will diagnose diabetes. You can reduce your risk of high fasting blood sugar by eating your dinner earlier the night before.
If your level is between 7.8 – 11.0 mmol/L, this indicates that you have prediabetes. Random blood glucose test. If your healthcare team suspects you may be at high risk for diabetes, they may draw your blood to be tested when you visit them, regardless of whether you have been fasting or have eaten recently.
For most people without diabetes, normal blood sugar levels are: between 4 and to 6 mmol/L before meals. less than 8 mmol/L two hours after eating.
The rationale for wiping away the first drop of blood is that the alcohol in the prep pad, and consequently on the fingertip, may alter values. However, this rationale is controversial and techniques vary among nurses and facilities. Additionally, not all patients are able to produce a second drop of blood.
Adult patients
Puncture the skin with one quick, continuous and deliberate stroke, to achieve a good flow of blood and to prevent the need to repeat the puncture. Wipe away the first drop of blood because it may be contaminated with tissue fluid or debris (sloughing skin).
The fingers can become stiff and difficult to move. If diabetes has been poorly controlled for years, it can feel like you have pebbles in your fingertips. Hard, thick, and swollen-looking skin can spread, appearing on the forearms and upper arms. It can also develop on the upper back, shoulders, and neck.