This post was initially released on October 25, 2020. It has been updated.
Intermittent fasting in diabetics has many benefits. It reduces blood sugar, lowers weight, triglycerides, total cholesterol, and decreases the need for medications. However, people with Type 2 diabetes or adult-onset diabetes who would like to do intermittent fasting should avoid complications.
Possible Complications of Intermittent Fasting When taking Diabetes Medications
Dehydration and Electrolyte Problems
As the body responds better to insulin during intermittent fasting, excess water gets flushed out together with salts like sodium and magnesium in the urine. This is good because it lowers blood pressure and weight and decreases any swelling in the legs.
However, if the fluid loss is more than the fluid intake, then dehydration can happen. That can manifest as dizziness, insomnia, passing out, falls, headaches, weakness, and lightheadedness. Adequate water and added salt intake will prevent dehydration.
Hypoglycemia
People with diabetes have elevated blood sugars that can cause complications like heart attacks, stroke, gangrene, kidney failure, and blindness down the road. That is why medications to lower blood sugar are prescribed. However, the medicines do not address insulin resistance, which is why complications still happen.
Intermittent fasting allows the body to be sensitive to insulin again and lowers blood sugar. Consequently, hypoglycemia can happen when certain medicines are taken while fasting.
Hypoglycemia means low blood sugar. The symptoms are irritability, confusion, sweating, and decreased level of consciousness.
In extreme, it can present as stroke-like symptoms, and it has to be ruled out when someone presents with stroke-like symptoms in the emergency room. Low blood sugar can even lead to coma and death if not recognized and treated.
There is a condition called Hypoglycemia Unawareness. In this situation, the person has very low blood sugar but does not have any symptoms until their consciousness deteriorates. That is why constant monitoring of blood sugar is essential. People with diabetes should have a glucometer.
Who Should Not Fast?
- Pregnant Diabetics
- Persons with dementia
- Children
- Anyone with a history of eating disorders
- People who had organ transplants on immunosuppressants.
Diabetes medications: What to stop and what to continue
Metformin
Metformin is effective in diabetes and inexpensive. It lowers the blood sugar production by the liver, which contributes to the high blood sugar in diabetes. It also decreases the intestinal absorption of sugars, increases glucose use by the body, and increases insulin sensitivity.
Metformin has a low risk of hypoglycemia and can be continued with intermittent fasting. Glucophage, Glucophage XR, Glumetza, Fortamet are brand names of metformin.
Sulfonylureas
Sulfonylureas like glyburide, glipizide, and glimepiride stimulate the pancreas to produce more insulin. The higher insulin levels lower the blood sugar. But sulfonylureas have a side effect. Studies have shown that people who take sulfonylureas tend to have worse outcomes if they develop a heart attack.
Read: Intermittent Fasting vs. Sulfonylureas: Heart Attack Outcomes
Long-acting sulfonylureas like glyburide (DiaBeta™, Micronase™, Glynase™, Glynase PresTab™), glipizide (Glucotrol™, GlipiZIDE XL™, Glucotrol XL™), and glimepiride (Amaryl™) can cause hypoglycemia during intermittent fasting. The doses should be reduced or withheld if taken the night before or the day of the fasting.
Meglitinides
Meglitinides are newer short-term acting sulfonylureas. Nateglinide (Starlix™) and repaglinide (Prandin™) should be withheld during meals without carbohydrates.
Insulins
Injected or inhaled insulin lowers blood sugar by storing what we eat into fat and muscles. However, if a person is inactive, the calories get primarily stored in fat.
All types of injected insulin, whether short or long-acting, can lead to weight gain and worsen obesity. Moreover, injected insulin in Type 2 diabetes worsens the preexisting hyperinsulinemia, which is why insulin is the last recourse in patients with Type 2 diabetes.
There is a high risk of hypoglycemia using long-acting insulins like NPH (Humulin™, Novolin™), Levemir (Detemir™), and Glargine (Basaglar™).
Insulin taken after meals like insulin lispro (Humalog™, Admelog™, Humalog KwikPen™, Lyumjev™), aspart insulin (Novolog™, Fiasp™, NovoLog FlexPen™, NovoLog PenFill™), and insulin glulisine (Apidra™, Apidra SoloStar™)also have a high risk for hypoglycemia, and blood sugar readings should be checked closely and proactively.
In prior studies of intermittent fasting on patients taking insulin, the doses were decreased by 50% and sometimes 75%. However, there were still some who had hypoglycemia, which is why constant monitoring and supervision are essential.
SGLT2 Inhibitors
SGLT2s like dapagliflozin (Farxiga™) and empagliflozin (Jardiance™), and canagliflozin (Invokana™) lowers the blood sugar by making the kidneys eliminate more sugar in the urine.
SGLT-2 inhibitors do not usually cause hypoglycemia. But since they eliminate sugar and water thru the urine, there may be a danger of dehydration and kidney injury, especially if intermittent fasting is also practiced. It is better to skip this medicine during fasting days or drink more water.
Additionally, people taking water pills that increase urine output, like furosemide (Lasix™) and hydrochlorothiazide for high blood pressure or heart failure, may need to reduce their dosage if on intermittent fasting to prevent dehydration and kidney injury.
DPP4 Inhibitors
DPP4s or Dipeptidyl peptidase inhibitors like saxagliptin (Onglyza™) and sitagliptin increase insulin secretion. They also prevent glucagon from increasing blood sugar after a meal. Side effects are sore throat, stuffy nose, upset stomach, and diarrhea. DPP4s can be continued.
TZDs or thiazolidinediones like pioglitazone (Actos™) and rosiglitazone (Avandia™) lower blood sugar by depositing them into subcutaneous fat. They have a low risk of hypoglycemia and can be continued.
Glucagon-Like Peptide-1 (GLP-1) Receptor Analogues
GLP-1 drugs lower blood glucose if carbohydrates are included in the meal. Dose adjustment for once-weekly injections cannot be adjusted. A daily injection of liraglutide (Victoza™) can be continued because the risk of hypoglycemia is low. Lixisenatide (Lyxumia™ or Adlyxin™) is used to control postprandial hyperglycemia and thus can be withheld during IF days.
Alpha Glucosidase Inhibitors and Bile Acid Sequestrant
Acarbose (Glucobay™, Precose™, and Prandase™) and Miglitol (Glyset™) delays carbohydrate digestion. The result is lower glucose levels. They can be skipped on meals without carbohydrates, not because of hypoglycemia, but they are not needed in those situations and save money.
Colesevelam (Welchol™ and Cholestagel™) sequesters bile and lowers blood glucose and cholesterol absorption. They can be skipped during intermittent fasting; however, they should be continued if they are taken to lower cholesterol.
Summary
Drugs can cause hypoglycemia while intermittent fasting:
- Insulin
- Sulfonylureas – glyburide, glipizide, and glimepiride
- Meglitinides – nateglinide (Starlix™), and repaglinide (Prandin™)
Medications with low risk of Hypoglycemia while fasting
- Metformin when taken alone
- DPP4s – saxagliptin (Onglyza™) and sitagliptin(Januvia™)
- TZDs – pioglitazone (Actos™) and rosiglitazone (Avandia™)
- Liraglutide (Victoza™)
Not needed when intermittent fasting
- SGLT2s like dapagliflozin (Farxiga™) and empagliflozin (Jardiance™), and canagliflozin (Invokana™)
- Lixisenatide – not needed during fasting days
- Acarbose (Glucobay™, Precose™, and Prandase™) and Miglitol (Glyset™)
- Colesevelam (Welchol™ and Cholestagel™). Continue if used to lower cholesterol
What about combination medicines?
Some diabetes medications are combinations of the above, like Metaglip, a combination of glipizide and metformin. In a drug combination, if one drug can cause hypoglycemia like glipizide in this case, then it should be skipped because it can cause hypoglycemia even though metformin is OK to take alone.
Be aware that other medicines can cause drug-induced low blood sugar, including:
- Beta-blockers (such as atenolol or propranolol overdose)
- Cibenzoline and quinidine (heart arrhythmia drugs)
- Indomethacin (a pain reliever)
- Medicines that fight infections (such as gatifloxacin, levofloxacin, pentamidine, quinine, trimethoprim-sulfamethoxazole)
If you plan on doing physical activity while fasting, be aware that it can also lower blood sugar. Ensure that you have a sugary drink if you plan to be physical activity outside while fasting.
Steps before for intermittent fasting
- Talk to your physician about your plans to do intermittent fasting. Some physicians may not agree with the method and dissuade you from doing so.
- Check and record your weight and waist circumference for baseline.
- Know your last glycosylated hemoglobin or HbA1c to know how your blood sugar has been controlled the past three months
- Be familiar with your list of medicines and all the doses.
- Check your blood sugar in the morning before breakfast and after every meal.
- Check the blood sugar every 2 hours if on insulin and every 4 hours for someone taking sulfonylureas.
- Personal continuous glucose monitoring systems like Dexcom® have hypoglycemia alerts. In contrast, Abbott Freestyle Libre System® has no hypoglycemia alert. These systems allow frequent testing without additional expense or discomfort.
Medication adjustments may need to be continued the longer you fast. That is why the blood sugars should be recorded. This will help your physicians adjust your diabetes medicines. As weight loss happens, the risk of hypoglycemia increases; therefore, medication adjustments should be made as required.
Recording your blood pressure and heart rate is also a good idea since the decrease in weight will lower your blood pressure. It is possible to be a diet-controlled hypertensive.
Don’t forget to increase fluid intake since water from food is also cut down. Feelings of fatigue and weakness can be from dehydration, and SGLT2 inhibitors, diuretics, and other anti-hypertensive drugs may need to be withheld.
Always talk to your doctor when starting an intermittent fasting program.
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Reference:
Grajower MM, Horne BD. Clinical Management of Intermittent Fasting in Patients with Diabetes Mellitus. Nutrients. 2019;11(4):873. Published 2019 Apr 18. doi:10.3390/nu11040873
Image credit: By Clinical Cases, Ilmari Karonen – Drawn in Inkscape by Ilmari Karonen based on w:Image: Incretins and DPP 4 inhibitors.jpg from http://casesblog.blogspot.com/2006/11/dpp-4-inhibitors-for-treatment-of.html (uploaded by author), CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=1540751
© 2018 – 2022 Asclepiades Medicine, L.L.C. All Rights Reserved
DrJesseSantiano.com does not provide medical advice, diagnosis, or treatment