Metformin is a common oral medication used to treat type 2 diabetes. It helps lower blood sugar levels by improving the way the body responds to insulin. Metformin is available by prescription as both generic and brand name drugs like Glucophage, Glucophage XR, Fortamet, and Glumetza.
Like most medications, metformin has an expiration date printed on the medication bottle or box. The expiration date helps ensure the effectiveness and safety of the drug during the time it is supposed to be used. However, metformin may still be effective past its expiration date in some cases.
What is metformin?
Metformin belongs to a class of medications called biguanides. It works by decreasing the amount of glucose (sugar) released by the liver and increasing the body’s response to insulin. Insulin is a hormone that allows glucose to enter cells and be used for energy.
In people with type 2 diabetes, the body either does not produce enough insulin or becomes resistant to insulin’s effects. This causes high blood sugar levels in the body. Metformin helps improve blood sugar control in combination with diet, exercise, and other diabetes medications.
The most common uses and dosages of metformin include:
– Treatment of type 2 diabetes in adults and children over 10 years old. The starting dose for adults is typically 500-1000 mg taken twice daily or 850 mg taken once daily. The dose may be increased in 500 mg increments up to 2000 mg per day.
– Treatment of polycystic ovary syndrome (PCOS) in women. The typical starting dose is 500 mg taken twice daily up to 1500 mg per day.
– Prevention of type 2 diabetes in people at high risk (prediabetes). The dose is usually 850 mg taken twice daily.
Metformin is available as immediate-release tablets, extended-release tablets, and oral solution. The extended-release forms help maintain more consistent metformin levels over time.
How long is metformin effective after the expiration date?
After the expiration date passes, a medication may not have the full effectiveness and potency that is expected from the active drug. However, expired medications do not usually become harmful immediately after the expiration date. Instead, drug products slowly break down over time after their listed expiration date.
With metformin, several factors determine whether it may still work past its expiration date:
1. Storage conditions
How metformin was stored after being dispensed from the pharmacy can affect its duration of stability. If it was stored according to the manufacturer’s recommendations, it is more likely to last.
Metformin should be stored at room temperature away from excess heat, moisture, and direct light. Extreme storage conditions like high temperatures and humidity can accelerate drug degradation.
2. Formulation type
Extended-release or long-acting metformin products, like metformin ER tablets and suspensions, tend to be more stable than immediate-release tablets and last longer past their expiration date.
The special polymer coatings used in extended-release metformin regulate the rate of drug release over time. This can help the medication remain effective if some degradation has occurred.
3. Expiration date
The actual expiration date listed on metformin products can provide an indication of when it may start to lose potency. As a general guide:
– 1-2 years past expiration: The medication has likely retained most of its effectiveness. However, there is some loss of drug stability and strength.
– 3-5 years past expiration: Questionable effectiveness. The drug has undergone more significant degradation but may still have some activity.
– 5+ years past expiration: The drug may have little to no activity left. Effectiveness cannot be relied upon.
Testing shows that immediate-release metformin retains around 90% of its potency up to 5 years past expiration when properly stored. The extended-release forms may retain potency even longer, up to 7-8 years when kept under ideal conditions.
Does degradation affect safety?
While expired metformin may lose some effectiveness over time, it does not appear to become toxic or dangerous to take.
Outdated drugs do not suddenly become harmful on their expiration date. When drugs degrade, they slowly break down into inactive components. Metformin simply turns into derivatives that likely have reduced glucose-lowering effects compared to the original active medication.
No cases of toxicity have been reported from taking degraded metformin. Therefore, taking metformin past its expiration date is not considered dangerous. However, the medication may not work as well to control blood sugar levels.
Can expired metformin make you sick?
Metformin is not known to make people sick when it expires and naturally degrades over time.
Some common side effects of metformin can include:
– Digestive problems like diarrhea, nausea, vomiting, gas, stomach pain
– Metallic taste in the mouth
– Loss of appetite
– Headache
These metformin side effects are usually more prominent when first starting the medication. The body typically adjusts to the side effects over days to weeks of continued use.
There have not been reports of expired or degraded metformin causing unusual side effects. The medication does not appear to break down into toxic substances.
However, people who are sensitive to metformin when they initially start taking it may also be more prone to side effects from degraded metformin. The reduced potency may also interfere with effectiveness.
Can metformin expire?
Yes, metformin does have an expiration date and can expire. Most metformin products have a listed shelf life of about 2-5 years from the time of manufacture.
The expiration date is an estimate by the manufacturer of when the medication reaches a point of substantial degradation. After this date, there is no guarantee the product meets the requirements for identity, strength, quality, and purity.
While expired metformin may still retain some potency, it is no longer considered stable or completely reliable per the standards. The medication has likely started degrading and is nearing the end of its shelf life.
For this reason, pharmacists will typically not dispense metformin or any drug past 1 year after its expiration date as a safety measure.
How can you tell if metformin has expired?
To determine if a metformin product is expired, check the expiration date printed on the medication bottle, box, or blister pack. The expiration date is usually printed with the month and year of expiry, such as “Exp 03/2024.”
Signs that metformin may be expired or degrading:
– The medication is past the labeled expiration date
– The color and appearance of the pills look slightly degraded
– The pills smell different than normal
– The effectiveness seems diminished or lasts for a shorter time
If your metformin prescription seems less effective and you notice any signs of degradation, check the expiration date. Expired metformin may need to be replaced with a new prescription.
Is it bad to take expired metformin?
Taking expired metformin is not recommended but is generally not considered dangerous, based on available data.
The main risks and concerns with taking expired metformin include:
– Reduced effectiveness: Outdated metformin may not work as intended to lower blood sugar due to degradation of the active ingredients. Loss of potency can affect blood sugar control.
– Potential side effects: Expired metformin could potentially cause more gastrointestinal side effects like diarrhea or nausea if the medication has substantially degraded.
– Dosing accuracy: The actual dose of metformin in each pill may be reduced in expired medication, making it harder to achieve the intended therapeutic dose.
To avoid issues with expired metformin, it is advisable to not use metformin past its labeled expiration date. Make sure to get metformin prescriptions refilled before running out of non-expired medication.
However, taking recently expired metformin in an emergency situation is unlikely to cause harm. Just be aware the medication may not work as well and monitor your blood sugar closely.
Does metformin stop working after expiration?
Metformin does not necessarily stop working right after its expiration date, but it does begin losing potency over time. The medication slowly degrades when it expires.
Here’s how metformin expiration affects the drug’s effectiveness:
– First year after expiry: Around 5-10% loss of drug activity. Metformin likely still works well.
– Second year after expiry: Up to 20% degradation. Slightly reduced strength and duration of action.
– Third year after expiry: Around 30% degradation. Noticeably weaker therapeutic effect.
– Fifth year after expiry: Up to 50% loss of efficacy. Poor blood sugar control.
While these percentages are estimates, studies show the drug’s glucose-lowering powers do progressively drop off after expiration in correlation with the degree of degradation.
Expired metformin may still have some effect, but after about 3-5 years past expiration, its strength becomes significantly impaired to rely on. Monitoring blood sugar is important if taking expired metformin.
How long does metformin take to leave your system?
Metformin takes between 6 to 8 hours on average to get eliminated from the body. This means metformin has a reasonably short half-life of 4 to 8 hours.
However, metformin’s effects on lowering blood sugar can persist for 12 to 24 hours due to its mechanism of action.
Factors that affect how fast metformin is eliminated include:
– Dose – Higher doses take longer to clear from the body
– Formulation – Extended-release metformin stays in the body longer
– Kidney function – Metformin is cleared slower in kidney impairment
– Age – Faster clearance is seen in younger people
– Hydration – Dehydration can delay metformin excretion
Since the kidneys filter out and remove metformin from circulation, any kidney issues can substantially increase the time metformin stays working in the body. For this reason, metformin doses need adjustment in patients with chronic kidney disease.
In most cases, metformin’s effects wear off within a day as it is eliminated. This timeframe is important when stopping metformin before procedures or when switching between long-acting and regular formulations.
Does metformin expire if not refrigerated?
Metformin does not require refrigeration and can be kept at normal room temperature. Storage conditions play an important role in the stability and shelf life of medications.
For metformin, not needing to be refrigerated prevents unnecessary degradation. According to the manufacturer, metformin tablets and oral solutions can be stored between 68°F and 77°F (20°C and 25°C).
Avoiding excess heat and humidity helps prevent metformin from expiring faster than its listed expiration date. Storing in a cool, dry area keeps metformin active longer. On the other hand, high temperatures and moisture can accelerate drug breakdown.
Refrigeration is not recommended and might actually lead to faster drug expiration. Cooler temperatures can cause moisture condensation inside containers, accelerating metformin degradation.
As long as room temperature conditions are maintained, metformin expiration is not accelerated compared to being refrigerated. Proper storage out of heat and direct light will help metformin remain stable up until its labeled expiry date.
Can you freeze metformin?
Freezing is not recommended for storing metformin. The manufacturer states metformin should be kept at controlled room temperature between 68-77°F (20-25°C) away from excessive moisture.
Freezing metformin could potentially cause subtle changes to the medication over time:
– Freezing may damage the tablets through fracturing or the development of cracks. This can change the drug release.
– Moisture condensation can occur when thawing after removing from the freezer. Increased moisture damages tablets.
– Active ingredients may become unstable when frozen. Metformin degradation is accelerated.
For these reasons, freezing is generally not advised for any extended-release tablets or capsules. The altered drug release could make metformin less effective or tolerable when thawed.
Immediate-release metformin tablets may physically withstand freezing better than extended-release forms. But freezing still risks increased moisture exposure and instability of active ingredients.
Keep metformin stored in its original container at room temperature around 70°F (21°C). Avoid direct sunlight and humidity. This helps prevent freezing or excessive heat from degrading metformin more rapidly.
Does metformin really expire?
Yes, metformin does expire and has a set expiration date listed by the manufacturer and approved by the FDA. Like all drugs, metformin has a stable shelf life period where its effectiveness and chemical integrity are reliably maintained.
However, “expiration” is a gradual process rather than suddenly becoming ineffective or dangerous on the exact expiration date. When properly stored, metformin seems to slowly lose potency over time after its listed expiry date.
Up to 5 years past its expiration date, immediate-release metformin may still retain around 90% strength if kept under ideal conditions. Extended-release metformin may last even longer.
While expired metformin is not considered harmful to take, its diminishing effectiveness eventually makes it unreliable for treating diabetes. Expiry dates on medications should be heeded to ensure you get the advertised therapeutic benefits.
Checking expiration dates and not using degraded metformin helps prevent ineffective blood sugar management. However, taking recently expired metformin is unlikely to pose safety concerns based on the gradual stability decline.
Does metformin expire after 28 days?
No, metformin does not expire after only 28 days. Most metformin products have an expiration date of 2-5 years from the original manufacturing date if stored properly.
The typical shelf life of metformin is:
– Immediate-release tablets: 2-3 years
– Extended-release tablets: 3-5 years
– Metformin oral solutions: 3 years
After being dispensed from the pharmacy, metformin can be used up until its printed expiration date on the medication packaging.
A 28-day expiry applies to opened metformin bottles. Once a bottle is opened, the shelf life is reduced to 28 days for immediate-release metformin liquids and tablets. Extended release forms may last about 60 days after opening.
The shortened expiry after opening helps prevent possible contamination and accelerated degradation. To maximize shelf life, metformin bottles should be discarded on day 28 after opening.
For unopened metformin products, the expiry ranges from 2-5 years. Always check manufacturer packaging for the applicable expiration date based on the formulation. Properly stored metformin does not expire in just 28 days.
Does heat affect metformin?
Yes, exposure to excessive heat can affect metformin’s potency and cause it to degrade and expire faster. Metformin should be stored at controlled room temperature between 68-77°F (20-25°C).
Heat can accelerate the breakdown of metformin’s active ingredients. Temperatures above 30°C (86°F) are considered excessive and can shorten metformin’s shelf life.
Leaving metformin tablets in hot environments like inside hot vehicles or near heat sources can increase degradation. High humidity also exacerbates heat damage.
Signs of heat degradation include:
– Tablets appear discolored, melted, or cracked
– Medication smells different or has altered odor
– Effectiveness seems diminished
Heat can also damage extended-release formulations. The special polymer coatings regulating metformin release may breakdown when exposed to high temperatures for a prolonged period.
To keep metformin stable for as long as possible, avoid storage in hot places. Do not leave metformin tablets loose in a hot car. Keep metformin away from heat sources and direct sunlight.
Proper room temperature storage will prevent excess heat from accelerating metformin expiration before the labelled expiry date.
Can you still take metformin after expiration?
Metformin can still be taken and may work to some degree after it is expired. However, it is not recommended to take metformin past the manufacturer’s labeled expiration date.
Up to about 5 years after expiration, metformin may retain around 90% potency if stored properly. But there is diminished stability guarantee after the listed expiry date.
The risks of taking expired metformin include:
– Loss of effectiveness at lowering blood sugar due to degraded active ingredients
– Potential increase in side effects like diarrhea or nausea
– Inaccurate dosing since each pill may have reduced medication
While not necessarily toxic, using degraded expired metformin can make blood sugar management more difficult. The medication may not provide its full glycemic control effects.
Before taking expired metformin, talk to your pharmacist or doctor to see if it can still be used safely. They may recommend getting a new prescription with non-expired medication for the best therapeutic results.
Monitor blood sugar closely if relying on recently expired metformin in an emergency until the prescription can be refilled. But avoid using metformin that is more than 3-5 years past expiration.
What is the shelf life of metformin?
The shelf life or expiry period of metformin depends on the formulation:
– Immediate-release metformin tablets: 2-3 years
– Extended-release metformin tablets: 3-5 years
– Metformin oral solutions: Around 3 years
– Metformin powder for suspension: 3 years
These shelf lives apply to unopened metformin stored properly at controlled room temperature. Avoiding excess heat, moisture, and direct light will help metformin remain stable up to its listed expiration date.
Once opened, immediate-release metformin liquids and tablets expire after 28 days. Extended-release formulations may last 60 days after opening.
The manufacturer performs ongoing stability testing to determine shelf life. This ensures the medication maintains identity, strength, quality, and purity up until expiry.
While metformin may work past its labeled shelf life, effectiveness declines due to progressive drug degradation. following the manufacturer’s expiration dates helps optimize metformin’s glycemic control.
Conclusion
Metformin starts degrading slowly after its listed expiration date, leading to diminished efficacy over time. However, metformin does not appear to become toxic after it expires. Taking recently expired metformin is unlikely to cause harm based on current evidence and may provide some blood sugar-lowering effect.
To ensure ideal effectiveness, metformin should be discarded once it reaches its printed expiration date. Check that you have enough non-expired medication before running out of your current prescription. Properly storing metformin can help maximize shelf life up to the labelled expiry period.
While not ideal, taking expired metformin in an emergency situation is fairly low risk. Just closely monitor your blood sugar for reduced glycemic control. Avoid using metformin more than 3-5 years past expiration as potency substantially declines. Consult your doctor or pharmacist if you have concerns about taking expired metformin.
