At what time should I take metformin the day before an glucose tolerance exam to diagnose diabetes?

A year ago my sugar and insulin numbers where too high. My doctor prescribed metformin and told me my numbers should improve if I lost the weight (I was overweight at that time). I lost all the weight and I want to do the “glucose tolerance test” again to confirm or discard the possibility of having diabetes. At what time should I take the metformin the day before the test? How long does metformin stay in your body?? I do not want metformin to mask/change my glucose/insulin numbers.
THE TOLERANCE TEST I AM DOING IS FOR DIAGNOSING DIABETES, NOT TO MEASURE METFORMIN (MEDICATION) EFFECTIVENESS

[WaveRider]

Metformin will be in your system for 96.8 hours i.e. 4 days (5.5 x 17.6 hours). Stop taking it 4 days before only with doctors consent.

"The fact that metformin stays in system for 4 days, does that mean that metformin is still effective????"
As you'll see below, 90% is eliminated during the first 24 hrs, the remaining 10% takes up to 4 days to flush from your system. Talk to your pharmacist about its lifespan effectiveness after 24 hrs.

Following oral administration, approximately 90% of the absorbed drug is eliminated via the renal route within the first 24 hours, with a plasma elimination half-life of approximately 6.2 hours. In blood, the elimination half life is approximately 17.6 hours, suggesting that the erythrocyte mass may be a compartment of distribution.

[WaveRider]

Call your doctor. Since your doctor prescribed the Metformin he/she will provide you with instructions on how to prepare for your test.

Repost from
At what time should I take metformin the day before an glucose tolerance exam?
by cookieN, Feb 13, 2011 05:02PM

[cookieN]

The thing is that my doctor is measuring my glucose control with medication and medication effectiveness. What I want is to know what my real numbers are without the aid of the medication.

This, because I´ve noticed that the past week I´ve been getting glucose numbers around 70 two hours after meals (with medication). Since they are fine or low, could that mean I do not need the medication?

[WaveRider]

Metformin has an elimination half-life of approximately 17.6 hours. It is not metabolized, but secreted in the urine.

It takes approximately 5.5 x elimination half life's for a medicine to be cleared from your system, therefore it'll be in your system for that long.

So Metformin will be in your system for 96.8 hours i.e. 4 days (5.5 x 17.6 hours).

http://www.drugs.com/answers/how-long-does-glucophage-metformin-stay-in-system-269979.html

If censored the web site is drugs dhot com

You must first call your doctor and inform him/her of your intentions to halt Metformin to test you glucose "clean". Stopping without doing so is inadvisable.

I will comment on insulin testing in your other post.

[cookieN]

This is what I got from what I read.
a. Half life of metformin is 17.6 hours
b. Metformin is cleared from system in 4 days.

What I don´t understand is how many hours before should I take metformin for it not to effect/vary my blood tests results?
Should I stop taking it 17,6 hours before, or stop taking it 4 days before.

The fact that metformin stays in system for 4 days, does that mean that metformin is still effective????

[WaveRider]

Metformin will be in your system for 96.8 hours i.e. 4 days (5.5 x 17.6 hours). Stop taking it 4 days before only with doctors consent.

"The fact that metformin stays in system for 4 days, does that mean that metformin is still effective????"
As you'll see below, 90% is eliminated during the first 24 hrs, the remaining 10% takes up to 4 days to flush from your system. Talk to your pharmacist about its lifespan effectiveness after 24 hrs.

Following oral administration, approximately 90% of the absorbed drug is eliminated via the renal route within the first 24 hours, with a plasma elimination half-life of approximately 6.2 hours. In blood, the elimination half life is approximately 17.6 hours, suggesting that the erythrocyte mass may be a compartment of distribution.

[cookieN]

THANK YOU so much for your detailed response. It is very useful.

[WaveRider]

You're welcome. Glad to be of help.