One Genuine Risk of Starting a Low Carbohydrate Diet


If you’ve been reading my stuff for any length of time, you know that I think a low carbohydrate diet is not only safe, but beneficial.  It will not make your muscle mass waste away.  It will not weaken your bones. It will not cause your kidneys to, as we say here on the intertubes, asplode.

There is, however, one warning I must give about the transition to a low carb diet, and it’s a very serious warning, so please pay attention.

Many people come to carbohydrate restriction after years of not only obesity, but of ill health.  Indeed, many have been caught in an ugly downward spiral, eating less and less fat, more and more “healthy” whole grains, fruits, and the like, only to see their health, and especially their glucose control, deteriorate.  Consequently, many people are on numerous medications when they decide – often as a last ditch effort – to give a low carbohydrate diet a try.

The thing you must know and keep in mind is that carbohydrate restriction is such a dramatically effective intervention that many medications will need to be adjusted immediately.  This is particularly true of all blood sugar medications, and absolutely vital in the case of insulin and hypoglycemic drugs.  Dosages for these medications are usually predicated on the assumption that the patient will be eating a “normal balanced diet,” or even a low fat diet centered on “healthy” carbohydrates.  If you keep taking that sort of dosage while knocking the carbs out of your diet, you can become nastily, even dangerously, hypoglycemic.  Insulin shock can kill you.  You do not want to screw around.

Dr. Eric Westman
Dr. Eric Westman

Dr. Eric Westman, perhaps the most important researcher into low carbohydrate diets today, has worked extensively with diabetics, both in his research and in his practice. His protocol is quite simple: he takes diabetics off about half of their insulin or other hypoglycemic medications on Day One of eating 20 grams per day or fewer of carbohydrate. They are told to monitor their blood sugar very closely, and to adjust the medication as before. Just about everyone has to reduce medication over time, and most need no medication at all if obesity was the cause of the diabetes.

Your doctor may or may not be hip to carbohydrate restriction.  It’s my feeling that if your doctor is not, if he or she is still pushing a low fat/high carb diet for diabetics, you need a new doctor.  Furthermore, I must state clearly here that I am not a doctor, nor do I play one on television.  I cannot give you medical advice.  What I can tell you is that it is downright dangerous to keep taking a full dose of hypoglycemic medication while going low carb.

I can also tell you what I would do if I were a type 2 diabetic stuck with an uncooperative doctor: I would cut my medication dosage in half, and cut my carbs to Atkins Induction levels – 20 grams per day or fewer.  I would then check my blood sugar hourly (except while sleeping, of course – and if I got up to pee in the middle of the night I’d take it then, too.) for the first week or two, to make sure nothing was going horribly wrong.  However, I am something of a daredevil and self-experimenter, and my risks are my own to take.  Yours are the same; be careful, be informed.  In particular, read both Atkins Diabetes Revolution by Dr. Mary Vernon and Jackie Eberstein, RN, and Dr. Bernstein’s Diabetes Solution, by Dr. Richard Bernstein.

The take-home message here, though, is that you must not slash your carb intake while continuing to take your usual dose of hypoglycemic medication.  Must not, must not, must not.

To a lesser degree, you should be aware that blood pressure medication may well need to be adjusted.  Blood pressure predictably drops during the first couple of weeks of carbohydrate restriction.  You know how people like to say “You only lose water on that diet”?  It’s not true, but it is true that the super-fast five-to-ten pound loss people get in the first week is largely water.  That’s because dropping your insulin levels lets your body start eliminating sodium properly, and with it the excess water it’s been holding.  Losing that water lowers blood pressure, something the low carb detractors generally don’t mention.

For this reason, blood pressure medication may need to be reduced or eliminated on a low carbohydrate diet.  We don’t want you fainting when you stand up. Too, if you’ve been eating a low sodium diet for your blood pressure, be aware that, because of the beneficial effect on sodium excretion, salt restriction is generally not a good idea on a low carbohydrate diet.  (I personally have to make sure I get enough salt!)  If you have a blood pressure meter, use it.  At the very least, use the free machines showing up in so many pharmacies.  There is no substitute for awareness.

You’ll notice that both of these dangers are actually a result of improving health, and the consequent risk of an overdose of medication.  That’s a good thing in the long run, but the hazard is real, and it’s important that you be aware of it, especially as you adjust to this way of eating.

Again, information is your very good friend.  Read The New Atkins For A New You, by Dr. Eric Westman, Jeff Volek, and Stephen Phinney, and also Volek and Phinney’s The Art and Science of Low Carbohydrate Living (both excellent books to give your doctor, as well.)

Take care of yourself, be aware and informed, and self-monitor vigilantly in the first few weeks.

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  1. I am 80 years old and have been on Metformin for 4 years. My A1c is 6.4 and my blood glucose ranges fro 110 to 124. I have been told by my dr to stop drinking because it can result in lactic acidosis, and lactic acidosis can be indicated by a change in CO2, which in my case has been normal as indicated by my blood tests of the lat 5 years. I maintain a fairly low fat diet and eat low to average amounts of regular carbs. Any thoughts on my situation? I like my two drinks on a regular basis and some researchers ay the incidence of alctic acidosis is rare, 6 out of 100,000. My weight is 160 poinds and I am 5’9″ tall.

    • Dana Carpender

      I’m afraid I cannot speak to this issue, except to note that I like a couple of glasses of wine in the evening myself. What I would likely do in your shoes is go to PubMed and search “alcohol lactic acidosis”, “diabetes lactic acidosis,” “blood sugar lactic acidosis,” etc. I might also get a second opinion. (If you gather from this that I usually do my own research before consulting a doctor, you are correct.)

      Sorry not to be more help.

  2. I’ve formed a low carb system that is easy and works pretty good. If it’s 2 or 3 carbs per serving, no matter what it is, its on my diet. No other counting or portion control needed. And I always am SURE to keep the carbs as close to zero as possible for breakfast. I read somewhere that breakfast programs the day, so even if I slack off with fast foods in a hurry, I at least start the day as low as possible. I have these raspberries and strawberries in my backyard that do stall my weight loss, but I’m not about to share them with neighbors, dang it.

  3. Thank you so much for this article. This is an issue that is truly overlooked and can be devastating if not dealt with. We stress, over and over and over, to please seek the advice of your trusted medical professional prior to and during any weight loss program; low carb or not! Low carb weight loss works for so many of us. Overlooking common sense precautions, though, makes no sense at all. Thanks again for this great reminder.

  4. I became diabetic after a severe bout of pancreatitis and was put on Lantus insulin once a day. For a year I was a good little diabetic and followed the required low fat, high fiber diet and shot insulin once a day. After a year of that I decided to go low carb, lose weight and get OFF insulin. I took my blood sugar very frequently and, as it went down, reduced my daily dose by one or two (whatever the units are, (I started at 30 per day and ended at 0) Then I told my doctor I was no longer using the insulin – I have slacked off for awhile after losing 65 pounds and am about to try for the last 50 pounds I need to lose and will, once again monitor my sugar closely to make sure I don’t need to cut down on my oral medication. My A1c has been in the 6.1-6.2 range so everyone is happy with me at this point but I am hoping that by losing the rest of my weight I can get off the meds entirely. I will probably not be able to cut out the high blood pressure medication as that is caused by renal artery stenosis which will not be changed by this diet – at least I don’t think it will!

  5. I have a question–maybe I am uninformed…my thoughts are if you don’t have enough glucose in your system because of a low carb diet–won’t you go into a state of perpetual Ketoacidosis? wouldn’t this be the cause of the kidney damage, heart damage etc? Your body would be finding the next best source for sugar to feed itself. somewhere in that line is fat and as long as your water intake is good it can be metabolized…the left over is ketones…roaming around in the blood. What are your thoughts? Am I wrong in my thinking?

    • Ketosis, but not ketoacidosis. They are not the same thing. Ketoacidosis involves extremely high levels of ketones *and* blood sugar, plus a derangement of pH. Dietary ketosis — involving moderate levels of ketones — is a normal state that happens when your body is burning fat for fuel. You’re assuming that glucose is the “best” source of energy, but think about it: We have fat depots for a reason. We’re supposed to store fat when food supplies are rich, and live off those depots when it’s scarce, just like every other animal. Burning fat — and with fat, ketones — for fuel is how we utilize our stored fuel.

      Keep in mind that your body is perfectly capable of making what little glucose it actually needs — and it doesn’t need much — in the liver, a process called gluconeogenesis. Indeed, my liver is too good at gluconeogenesis; I have to watch my protein intake or I run slightly high morning blood sugar — and I rarely eat more than 20-25 grams of carbohydrate per day.

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