Do you have to take metformin?
by oobuc5
(somerset)
Question from oobuc5:
Do you have to take metformin? What happens if you do not take it?
I also find that when my blood sugar goes down to 4 or 5 mmol/L, I feel very sleepy, but I feel better around 6 or 7 mmol/L. I also worry about sugar information on bread and other foods.
Quick Answer
No, not everyone with type 2 diabetes needs metformin forever. But if it has been prescribed for you, I would not recommend stopping it without first speaking with your doctor. Your good readings may actually be partly because the medicine is working.
Answer by Dr. Albana Greca, MD, MMedSc
Hello,
I understand why this is confusing. You see a glucose reading of 4 or 5 mmol/L, which may look perfectly acceptable on paper, yet you feel sleepy and uncomfortable. At the same time, you may wonder whether you still need metformin when your readings seem good.
Do You Still Need Metformin?
That depends on the whole picture: your HbA1c, fasting and after-meal glucose, kidney function, weight, other medicines, side effects, and how long you have had diabetes.
Some people with early type 2 diabetes can maintain good control through food choices, physical activity, and weight loss when needed. Others continue to need metformin, and many do best with both lifestyle changes and medication.
The important point is that a normal blood sugar reading does not necessarily mean the medicine is no longer needed. It may mean the treatment is doing its job. If you are considering reducing or stopping it, take your glucose records to your doctor and discuss whether your current dose is still appropriate. You can also read more about metformin (Glucophage) and its side effects.
What Happens If You Stop It?
If metformin is helping control your diabetes, stopping it may allow your glucose and HbA1c to rise again. This may happen gradually, so you may not notice a difference immediately.
On the other hand, if your glucose is running lower than expected, you are having troublesome side effects, or your diabetes has improved considerably, your doctor may decide to reduce the dose, change the timing, use extended-release metformin, or consider another approach. Our overview of diabetes medicines, benefits, and side effects may also help you understand the options.
Why Do You Feel Sleepy at 4–5 mmol/L?
This is an important part of your question. For many adults with diabetes, glucose between about 4 and 7 mmol/L before meals may fall within their target range. However, your personal target should be decided with your healthcare team.
If your body has been accustomed to higher glucose levels for some time, a drop toward normal can sometimes make you feel as though your sugar is too low even when the meter shows 4–5 mmol/L. This is sometimes called relative hypoglycemia.
Metformin by itself does not usually cause true hypoglycemia. The risk is greater if you also use insulin or certain diabetes tablets, miss meals, drink alcohol, exercise more than usual, or become unwell.
If you feel sleepy, shaky, sweaty, dizzy, weak, hungry, confused, or faint, check your glucose and write down the reading, time, food, medication, and symptoms. A repeated pattern is much more useful to your doctor than a single number. See also how to tell when blood sugar may be too high or too low.
What Should You Look for on Bread Labels?
When you have diabetes, do not focus only on the word “sugar.” Bread is mainly a carbohydrate food, and starch is broken down into glucose during digestion.
I would look first at the total carbohydrate per slice, portion size, fiber, and ingredients. A wholegrain bread may produce a gentler glucose response for some people, but portion size still matters.
If bread from a bakery has no nutrition label, you can ask whether nutritional information is available. You can also learn a great deal from your own glucose response by checking before and around 1–2 hours after eating. Our guide to carbohydrates and the glycemic index explains this in more detail.
When to Get Medical Help
Speak with your doctor if these sleepy or “low” feelings keep happening. Seek urgent help for severe confusion, fainting, seizure, inability to swallow safely, repeated glucose below 4 mmol/L, very high glucose with vomiting or dehydration, chest pain, trouble breathing, or severe weakness.
Doctor’s Note
Please do not chase a particular glucose number simply because it looks “perfect.” What matters is safe, stable glucose control that you tolerate well. If you repeatedly feel unwell at 4–5 mmol/L, show your readings and symptoms to your doctor so your targets and treatment can be reviewed together.
Most Asked Questions
Can I stop metformin if my blood sugar is normal?
Possibly, but only after discussing it with your doctor. Your readings may be normal partly because metformin is working.
Does metformin cause low blood sugar?
Metformin alone rarely causes hypoglycemia. The risk changes if other glucose-lowering medicines, missed meals, alcohol, exercise, or illness are involved.
Is 4–5 mmol/L too low?
Not necessarily. It may be within target for many people, but symptoms matter too. A reading below 4 mmol/L is generally considered low and should be treated appropriately.
Related Questions
- Can other medicines affect diabetes and metformin?
- Can cephalexin affect blood sugar?
- Why isn’t my blood sugar going down?
Related Resources
- Glucophage side effects
- Diabetes medications: benefits and side effects
- Diabetes, carbohydrates, and glycemic index
- Blood sugar log sheet
Educational safety note: This information is for general education and does not replace medical advice from your own healthcare professional. Do not stop or change metformin or another diabetes medicine without discussing it with your healthcare provider.
Last reviewed: July 2026.
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