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HOMA Calculator

1. Where can I get a quick guide to the HOMA model?

The "Use and Abuse of HOMA modeling" paper [Wallace TM, Levy JC, Matthews DR. Diabetes Care (2004); 27(6): 1487-95] addresses most HOMA issues. Additional HOMA related papers are listed in publications.

2. What input values will the HOMA Calculator accept?

As HOMA is a steady state model, only clinically realistic values that would be seen in a fasting subject should be used. These are:

3. Why does the Excel version give errors for some input values?

Outside the accepted range (see Q2) calculation is often impossible. The Excel version gives an answer wherever possible but answers outside the accepted input range should be treated with caution.

4. I'm getting an error 'Run Time Error "13", Type Mismatch'?

This problem is resolved in version 2.2 and above. Please download the latest version.

5. I am having problems downloading the HOMA Calculator

There are known IE problems associated with some web browsers. You can overcome these by following the instructions given below:

6. I have downloaded and installed the HOMA Calculator but it will not work.

You must ensure that you have administrator rights on your computer. Please query this with your IT department. Typically you may see the following messages

7. Why does the HOMA Calculator return 'Unable to calculate' for certain input values?

The HOMA calculator is not running a simple equation to produce its answers. It is instead running very complex mathematical model of the human body. In order to produce the answers it chooses a starting point based upon the inputs value provided. It then iterates the model until it converges on the correct answer. Sometimes the model will not converge. Changing the inputs very very slightly will often change the starting parameters used for the model. This can lead to the model then being able to converge correctly and provide a working answer.

Our suggestion is to change the input values slightly below the actual value and then slightly above the actual value and check that the results returned are comparable.

8. When I try to open the HOMA calculator Excel spreadsheet and enter data I get an error message.

The installation program for the HOMA Calculator installs a library in your Windows system. If this file is moved after installation then the Excel spreadsheet will stop working. Re-instalation of the the program should solve the problem. It is also worth pointing out that the software must be installed on each machine you are going to use the Excel workbook on. Although you cannot move the HOMACore.dll you may copy, move or rename the Excel workbook that is used to perform the calculations.

9. Please can you provide the formulae used to calculate HOMA2 values?

The HOMA Calculator embodies the iterative structural model that simulates the physiological processes that influence circulating glucose and insulin levels in order to derive estimates of beta cell function (HOMA_%B) and insulin sensitivity (HOMA_%S). A full description of the first version of the model (HOMA1), and the updated and enhanced version of the model (HOMA2) are provided in the manuscripts listed on our HOMA publications web page.

The widely-used formulae available for HOMA1 provide only linear approximations of HOMA_%B and HOMA_IR, the inverse of HOMA_%S. These are:

HOMA1_IR = (FPI x FPG)/22.5
HOMA1_%B = (20 x FPI)/(FPG - 3.5)

The results obtained may differ considerably from HOMA1 computer-calculated values, especially for more extreme glucose and insulin values. For this reason, no attempt has been made to provide linear approximations of HOMA2 calculated values of HOMA_%B, HOMA_IR and HOMA_%S. The software needed to calculate HOMA2 values is available on this website for a variety of computing platforms, subject to the conditions specified on the downloads page.

Those wishing to incorporate HOMA2 estimations into other software packages should request information on the HOMA Calculator API, which provides Windows and Macintosh libraries for performing the calculations. This API is compatible with a large range of systems, including SAS.

10. Is there a normal range for HOMA values?

There is no absolute value for HOMA indices.¬† These will depend on the specific assays used for glucose, insulin and C-peptide. ¬†Because of this, there are no defined thresholds for ‘normal’ vs. ‘abnormal’ values. Please see the following document for further details.