Frequently Asked Questions
1. I have downloaded and installed the HOMA2 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
- -2147024770 automation error
- Code: 429 active X component can’t create object
- Setup fatal error: unable to generate installation log file
2. 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.
3. What input values will the HOMA2 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:
- Plasma glucose 3.5 to 25.0 mmol/L
- Plasma insulin 20 to 400 pmol/L
- Plasma specific insulin 20 to 300 pmol/L
- Plasma C-peptide 0.2 to 3.5 nmol/L
4. 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.
5. I'm getting an error 'Run Time Error "13", Type Mismatch'?
This problem is resolved in version 2.2 and above.
6. I am having problems downloading the HOMA2 Calculator
There are known IE problems associated with some web browsers. You can overcome these by following the instructions given below:
- Go to our website http://www.dtu.ox.ac.uk/homacalculator/download.php
- Right click and let go on the 'Windows' link under the ‘Download the HOMA2 Calculator’ heading
- Select 'Save target as...' from the menu that pops up
- Select a location for the file - use desktop for now to keep things simple – and save
- Close Internet Explorer and all other applications
- There should be an Icon on the desktop called ' HOMA2CalculatorWindowsSetup.exe'
- Double click this icon
7. Why does the HOMA2 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 HOMA2 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 HOMA2 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 HOMA2 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.
11. Can the HOMA2 Calculator use serum rather than plasma insulin values?
There are few data comparing simultaneous measurements of serum and plasma inulin values. The paper by Henderson (Henderson JR, Serum-insulin or plasma-insulin? Lancet. 1970;2:545-7) and a later letter (Henderson JR, Serum-insulin or plasma-insulin? Lancet. 1971;2:1430-1) explore this issue across a variety of different insulin assays and suggest that plasma measured values tend to be greater, with the magnitude influenced by the heparin content of plasma samples. The HOMA Calculator is designed to work with glucose and insulin values measured simultaneously in plasma. If serum insulin values are used instead, this should be noted as a limitation in any publications unless the laboratory concerned are able to derive a serum-to-plasma conversion factor for the insulin assay they are using.
12. Can the HOMA2 Calculator use serum rather than plasma glucose values?
When blood samples are correctly collected, handled and analysed either can be used by the HOMA2 Calculator as there should be no meaningful differences between the values obtained from serum or plasma. The paper by Frank et al. (Frank EA, Shubha MC, and D’Souza CJM. Blood Glucose Determination: Plasma or Serum? Journal of Clinical Laboratory Analysis 2012;26:317–320) suggests serum values to be 1.15% lower than plasma. It also highlights the well-recognised sample collection and handling problems that can result in substantially lower serum as well as lower plasma glucose values.
13. I am getting an error using HOMA2 in EXCEL on an M1 Mac
We have had a few reports of issues with the HOMA2 calculator for Excel on M1 Macs and we are working on updating it.
The Excel version uses a library, but the library has not been updated for the new Macs when running Excel natively.
Follow these instructions to run Excel in "Compatibiity" mode:
1. Quit Microsoft Excel (make sure it’s not running)
2. Select the Application in the Applications folder, and press Command-I
3. In the Info window, look for the option “Open in Rosetta”
4. Close the Info window and relaunch Excel
5. When you are no longer using the HOMA library you probably want to repeat these instructions and turn the option OFF, as it will have some impact on performance of Excel.
14. Who is the HOMA2 calculator Intended for?
The HOMA2 Calculator is intended for use by health care professionals to assist in the assessment of beta cell function and insulin sensitivity. It may be of assistance in the management of dysglycaemia or Type 2 diabetes but is not a replacement for formal medical assessment and not intended for use by patients unless in consultation with their trained medical adviser.