Insulin to Carb Ratios: How to Calculate Insulin Doses

Medically Reviewed By: Dr. Ashwini Sarode, M.B.B.S, Consultant Diabetologist January 3, 2022

Last updated on September 14th, 2023

If a person is living with insulin-dependent diabetes, carbs are counted precisely, and still struggling with postprandial (post-meal) high or low blood glucose levels, then his or her “insulin-to-carb ratio” might require modification. An insulin-to-carb ratio is a number that indicates the amount of rapid-acting insulin a person requires to cover a particular quantity of carb. This permits accurate dosing of insulin for meals or correction of high levels of blood glucose. In this article, what this insulin to carb ratio is, how to find this ratio, as well as the factors affecting it, are discussed.

Carbohydrate counting is a significant skill for understanding when a person is diabetic. Carb counting assists in getting the glucose level within the controlled limits. In addition, it offers flexibility to a person about what to eat and when to eat. This may help him or her feel more in control and self-assured while managing the condition.

What is an Insulin to Carb Ratio?

The insulin-to-carb ratio means the grams of carbohydrates one unit of rapid-acting insulin covers to make sure that blood glucose lies within the desired limit. The carb ratio is often set by a healthcare provider when diabetes is diagnosed but needs updating regularly. A carb ratio of 1:10 signifies that that one unit of rapid-acting insulin would pack 10 grams of carbohydrates. A higher ratio means that a person would require less insulin to cover the carbs.

insulin to carb ratio

For example:

If the carb ratio is 1:10 and a person consumes 30 grams of carbohydrates, then 3 units of rapid-acting insulin would be required to cover the meal (30 divided by 10). But, if the carb ratio is 1:15, then only 2 units of rapid-acting insulin would be required (30 divided by 15). A higher carb ratio implies less insulin. If the time of insulin is peaked with the meal, a precise carb count together with a precise carb ratio would imply that the blood glucose level must stay within the desired range as well as under 180 mg/dl (10 mmol/L).

If the insulin timing for the meal is off, however, the carb count and carb ratio are correct, then a person may notice his or her glucose level going somewhat out of range. And it must be back in limit within 90 minutes (being the average time insulin peaks). Also, it is vital to note that a person must subtract the fiber content present in a meal from the total carb count before calculating the insulin dose for the reason that fiber doesn’t break down fully in a person’s gut. And, hence fails to elevate the blood glucose levels. Dosing fiber might give rise to low blood glucose.

Also Read: Sliding Scale Insulin Therapy For Diabetes

Use an insulin to carb ratio if a person:

  • Is unsure that the child would consume all the carbs present in the meal
  • Is not hungry
  • Does not like particular food products served with a meal
  • Is having a meal packed with carbs
  • Is having a low-carb meal
  • Requires or wishes to have a larger snack

How to calculate Insulin to Carb Ratio(s)

If a person suspects that his or her carb ratio is off (often running high or low following meals might be an indication of that), it’s time to collect information in the form of blood glucose readings and perform some analysis. If good results are desired, then a good amount of data is a must. Just like other things associated with diabetes, it demands work but it’s worth it. The following four steps are must for a minimum of 4-5 days for collecting data to assess whether the carb ratio is appropriate. If there are no trends noticed after 4-5 days, then more data must be collected.

  • Concentrate upon one meal at a time (for instance, breakfast). Try to enjoy the meal at the same time of the day and consume similar foods and amounts for the data collection period (for this reason, breakfast is a good place to begin with as it’s simpler to consume the same thing for breakfast every day).
  • Ensure that the carb count is precise and continue with the similar carb ratio for the data collection period.
  • Try not to do anything that influences the level of blood glucose considerably right before or after the meal.
  • Be on top of the blood glucose evaluations or Continuous Glucose Monitor (CGM).
  • Evaluate the blood glucose prior to the meal.
  • Evaluate the blood glucose after the meal (90-120 minutes after injection).
  • After three to four days, a sufficient amount of data is needed to begin evaluating whether the carb ratio for this time of day is precise.

When a healthcare provider does the evaluation, the person concentrates upon whether the blood glucose was in the desired limit prior to the meal and whether the blood glucose return to a desired limit within one to two hours of the insulin injection.

Also Read: HbA1c Range Calculator

Let’s look at two diverse situations, assuming a meal of 30 carbs (that’s counted as precisely the moment it is possible) and an initial carb ratio of 1:10.

Blood glucose in-range prior to the meal, but high 90-120 minutes after

If the blood glucose is not back in range or coming down rapidly 90-120 minutes after a meal, a person’s carb ratio is too high. A person might consider trying to experiment with ratios under 1:10, possibly 1:9 or 1:8 is the correct ratio for the person. Think of, the lower the carb ratio, the more insulin a person requires per gram of carbs.

Blood glucose in-range prior to the meal, but low 90-120 minutes after

If the blood glucose is lower than the target range 90-120 minutes after the meal, the carb ratio is too low. A person might consider trying to experiment with ratios greater than 1:10, perhaps a person might require to go to 1:11 or 1:12. In addition, a person requires to consider if the timing for when a person uses the insulin is off. If a person has low blood glucose within half an hour to one hour of the injection, the food may not have been adequately digested yet and would hit the bloodstream later. A person might evaluate this by evaluating the blood glucose often and experimenting with using the insulin a little later.

Also Read:  What is Polydipsia?

Things that Affect Insulin to Carb Ratios

Bodies alter over time and so does the eating as well as exercise patterns. And as the body and daily routine modifications, a person may find that the carb ratio(s) requires adjustment.

Below are 5 things that might affect the insulin to carb ratios:

Time of day

A person may have observed that “carb ratio(s)” should be written as many individuals have more than one carb ratio. For instance, many are more insulin resistant in the morning hence they may require a reduced carb ratio for breakfast than they perform for lunch or dinner. Theoretically, a person might consume as many carb ratios as per liking, however, a majority of diabetes devices (apps, pumps, smartpens) have a restricted number.

Time of month (for females)

The shifting hormone levels of the menstruation cycle might have a considerable impact on the levels of blood glucose as well as insulin requirements. This might indicate that a person might require diverse carb ratios (and almost certainly basal insulin) for periods where a person is additionally insulin-resistant owing to hormonal alterations.

Type of meal: the impact of fat and protein

Carbs may be what’s getting converted into sugar in the bloodstream, however, it’s not the only macronutrient that might affect blood glucose. If a person might consume huge amounts of protein, he or she is presumably required to inject insulin to not notice an increase in blood glucose. If a person adds huge amounts of fat to a meal, he or she is most likely noticing a delayed liberation of the sugar into the bloodstream, which for a majority of individuals signifies that they require to use two insulin doses instead of just one (one with the meal as well as one sometime later).


If a person is more or less active than usual, he or she must consider that when a person calculates the insulin doses. If the person uses bolus insulin half an hour to one hour prior to a workout, he or she often requires lowering the dose by 25-75%. This is a large range and he or she requires to find the correct drop for him or her. If a person does resistance training or interval training, he or she may not require a reduction, he or she may even require an increase as these forms of workouts might increase the levels of blood glucose.


If a person’s body weight alters considerably, he or she would most certainly notice that the insulin requires alteration too.  The body fat percentage is enhanced in a significant manner, then the person may experience that more insulin would be required to cover up the meals. If a person gains a considerable amount of muscle mass, instead, he or she may notice that less insulin would be needed to cover the meals.

Tools for finding and remembering the carb ratios

The use of carb ratios is pretty simple if a person utilizes an insulin pump for diabetes management. Many pumps have a build-in bolus calculator (by which recommended dose can be calculated) and the medical team must have set it up for the person and trained about the way to use it. If that’s the case, a person requires concentration upon whether the ratios are precise. If a person manages diabetes using manual injections, then a “carb calculator” can be used for memorizing or writing down the ratio(s). The advantage of a good calculator is it keeps a track of active insulin (insulin that persists three to five hours in the body) and assists in tracking the injections and ratio(s).

To use an insulin-to-carb ratio, a person requires to:

  • Plan in advance and consume all of the meal.
  • Consume the rapid-acting insulin 15 minutes prior to eating.
  • The only time it is appropriate to use the rapid-acting insulin post-meal is for very young children who might not consume everything. If a child is using his or her insulin after they consume, they should use it the moment they complete eating, within half an hour of their first bite of food.
  • Using insulin after consumption would bring about high blood glucose just some hours later.
  • Using insulin prior to eating and then not eating all of the intended carbs would give rise to a low level of blood glucose when the rapid-acting insulin peaks.
  • If a person would be utilizing an insulin-to-carb ratio for computing the rapid-acting insulin doses, he or she would require being precise at counting the carbs and doing the calculation for dose computations.

So, if you want to keep your insulin-to-carb ratio within desired range, Breathe Well-being, a research-based diabetes reversal platform is the best for you. The company provides a constant patient care, reversal companions helping in diabetes awareness, customized nutrition therapy, fitness programs, face-to-face sessions with expertise coaches discussing carb counts, insulin dosages, medicines, etc. If a person aims towards attaining complete freedom from diabetes, he or she should go for diabetes reversal. And when, the concern of diabetes reversal comes, Breathe Well-being is just the best fit for any diabetic. For more information, quickly visit the website and grab the offers and deals. Happy living!!

Also Read: Janumet Tablets For High Blood Sugar


How do I calculate how much insulin to inject?

Divide the total carbs by the insulin to carb ratio. The result comes the amount of insulin units required.

How many insulin units do I require per carb?

The insulin-to-carb ratio signifies that a person would use 1 unit of insulin for a certain amount of carb. For instance, if the insulin-to-carb ratio is 1 unit of insulin for each 10 grams of carb (written 1:10), a person would use one unit of insulin for every 10 grams of carb he or she eats.

Which insulin is not adjusted for carb consumption?

Basal insulin (long-acting form of insulin) handles the sugar produced by your liver. If a person misses out any meal or consume a carb-free meal, basal insulin alone would be capable of keeping the blood sugar levels stable.



Last Updated on by Dr. Damanjit Duggal 


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