Keto & Fasting on Metformin or Insulin? A Doctor’s Guide to Safely Lowering Your Dose

This topic is the single most urgent and fear-laden issue in the entire comment landscape, mentioned over 20 times. Viewers find themselves in a dangerous paradox: they are inspired by the message that cutting carbs and fasting can reverse their condition, yet their prescribed medications—insulin, metformin, and others—are designed for a high-carb diet. Following the new advice without adjusting the old medication protocol creates a direct and immediate risk of hypoglycemia (dangerously low blood sugar), a condition that can be terrifying and, in some cases, life-threatening. The audience is caught between two conflicting sets of instructions, feeling both hopeful about reversal and terrified of the process.

The overwhelming concern is safety. Viewers are worried about causing a severe hypoglycemic episode—feeling dizzy, weak, shaky, and panicky—especially if they live alone. They are profoundly confused by the "insulin paradox": why they are prescribed more of the hormone that caused the problem in the first place. This leads to a feeling of being trapped in a medical catch-22, where doctors won't reduce medication until numbers improve, but the medication itself (particularly insulin) contributes to weight gain and seems to hinder progress. This cycle leaves them feeling frustrated, helpless, and ready to give up.

The most critical insight emerging from the expert advice and audience pleas is non-negotiable: You must partner with your doctor to systematically reduce medication as you reduce carbohydrates. These two actions must happen in tandem. The medications are a tool designed to manage the high sugar load from a standard diet. As you remove the sugar load, the tool becomes too powerful and must be dialed back carefully and methodically under medical supervision.

Only one creator in the analyzed sources provides direct, explicit guidance on the safety protocols for fasting while on medication. While the topic is frequently raised in the comments of other videos, those creators do not address the "how-to" of medication management in the provided transcripts.

• Dr. Jason Fung: In his video, Dr. Fung directly and responsibly addresses this critical issue. He states plainly that while fasting itself doesn't cause low blood sugar in a person without medication, it is a different story for those on diabetes drugs. His approach is clear:
  • ◦ Clarity: He explains that as you fast, your body naturally uses up its stored glucose. If you are also taking medication designed to lower glucose, your levels can "actually go too low".
  • ◦ Practicality: He gives a direct instruction: "it's really important to talk to your doctor anytime you change your diet to make sure that you don't need to make adjustments to your medications".
  • ◦ Unique Perspective: He reframes the need to reduce medication not as a problem, but as a victory. He states, "when you're reducing your medications for blood glucose that means your diabetes is actually getting better so that's a good thing not a bad thing". This empowers viewers to see medication reduction as a key sign of success on their journey to reversal.

Schedule an appointment with your prescribing doctor. Do not change your diet or medication dose yet. Your first action is to open a dialogue with the goal: "I want to use diet to reduce my need for this medication, and I need your help to do it safely."

• Mistake: Stopping medication "cold turkey" or drastically reducing it on your own out of frustration.
  Fix: Never stop or alter your dose without your doctor's explicit instruction. The risk of severe hypo- or hyperglycemia is too high. This is a partnership, not a solo mission.
• Mistake: Jumping into an aggressive fasting protocol (like OMAD or a 36-hour fast) while still on a full dose of medication.
  Fix: Start with gentle carb reduction first. Introduce time-restricted eating later, beginning with a modest 12-hour fast, and only with your doctor's awareness and a plan for adjusting meds.
• Mistake: Not testing your blood sugar enough because you "feel fine."
  Fix: When changing your diet on these medications, you must test more often than usual, not less. This is the only way to catch a potential low before it becomes symptomatic and dangerous.

• • "I am confused…if I am insulin resistant which means I make too much insulin, why am I prescribed SUs which are known to increase insulin. Isn’t that backwards?"
• • "I'm a type two diabetic and on Lantic solistar insulin. If I'm insulin resistant, why am I still taking insulin? Does this diet still work in my case?"
• • "How do type 1/ type 2 diabetics safely transition from being insulin dependent to being healthy, using your methods, as you rightly say changing your diet, which is all well and good, but would you still continue with your doctor's medications."
• • "Just started fasting, why is my body reacting differently to food? Before... my blood glucose would raise minimally... Ever since I started doing the 36 hour fast, every time I would break the fast my blood glucose would spike like crazy up to 200mg/dl and I would have to take more insulin than my prescribed amount"

Changing your diet with keto and fasting while on diabetes medication is like removing fuel from a fire while still aiming a firehose at it. At some point, you no longer need the firehose. However, turning it off requires a skilled hand and careful timing. The path to reversal is absolutely possible, but it is not a DIY project. It demands a new role for you—as an active, educated partner in your own health—and a collaborative relationship with your doctor. Safety through supervision is the first and most important step.