Knowing your family health history and sharing it with your doctor can help you avoid a life-threatening illness. One great example: Letting your doc know that your parent or sibling has diabetes will prompt her to screen you for early signs of the disease. If you test positive for prediabetes and make the recommended lifestyle, diet and exercise changes, you can cut your risk of developing full-blown diabetes by 58 percent.

Whether it’s breast or colon cancer, heart disease or vision loss, getting an accurate picture of which diseases have afflicted your family can help you head off potential problems before they start.

When gathering info, start with your parents and siblings. Explain that you’re collecting information from first- and second-degree relatives. Let them know that these details will benefit immediate and extended family, including grandparents, aunts, uncles and cousins.

A great way to track and store this info is with the U.S. Surgeon General’s My Family Health Portrait forms at http://www.hhs.gov/familyhistory/portrait/print/index.html.

To give you a better sense of how family history affects your own health, here are eight common inherited health conditions, the odds of developing them and the benefits of catching them at their most treatable stages.

Diabetes

Family link: Having one parent with diabetes raises your risk two to three times higher than the average. If both parents have type 2 diabetes, your risk is 5.6 times higher, say researchers from the University of Wisconsin. 

What you can do: Get a diabetes screening check earlier than age 45, the recommended age most adults should be tested. Your doctor will decide at what age to start and how often you’ll need to re-test based on other factors as well, including your weight, blood pressure and ethnic or racial background.

Heart Disease

Family link: If your mother or father had early heart disease, including heart attack in men before 55, women before 65, your heart disease risk is two to nine times higher than average. A brother or sister’s heart disease can raise your risk four times higher than a parent’s, according to a 2007 Harvard Medical School study published in the journal Circulation.

What you can do: Keep your blood pressure, cholesterol and triglyceride numbers healthy — talk with your doctor about when to start screenings and whether you need medications (such as cholesterol-lowering statins). Ask for advice on exercise and healthy eating. 

Breast Cancer

Family link: Having a mother, grandmother or daughter with breast cancer doubles a woman’s risk; having two first-degree relatives with it raises the risk five-fold. Women who have the BRCA-1 or BRCA-2 genetic mutation have an 80 percent chance of developing breast cancer. Men who carry these mutations are also at increased risk for breast cancer.

What you can do:The American Cancer Society (ACS) recommends women at high risk for breast cancer have a mammogram and a breast MRI every year beginning at age 30. (Talk with your doctor to determine the best age for you; some cancer centers say to begin 10 years earlier than the age at which your youngest relative was diagnosed with breast cancer). The ACS suggests all women have clinical breast exams by a healthcare practitioner starting in their 30s and say a monthly self-exam is an option that can help you become familiar with your breasts and notice changes more quickly. Men with a family history of breast cancer should discuss it with their doctor and find out the best screening plan for them. 

Colon Cancer

Family link: A family history increases your risk two to four times higher than average. Having three or more family members with colon cancer over at least two generations, with at least one before age 50, can be a sign of hereditary conpolyposis colorectal cancer (HNPCC). This set of gene mutations raises the risk for colon cancer by as much as 80 percent and also increases the risk for cancers of the stomach, small intestine, pancreas, uterus and ovaries.These mutations interfere with your body’s ability to repair damaged DNA.

What you can do: Schedule regular colonoscopies by age 20 to 25, or five to ten years before the earliest diagnosis in family, whichever comes first. Repeat every five years or as recommended by your doctor. If you have HNPCC or another genetic mutation that raises colon cancer risk, you may need an annual colonoscopy.

Ovarian Cancer

Family link: Ovarian cancer in a first-degree relative raises your own risk four-fold; ovarian cancer in second-degree relative increases your risk by 50 percent or more. A history of breast cancer ups your risk for ovarian cancer 40 to 80 percent and higher if you have a BRCA mutation.

What you can do: Experts recommend ovarian-cancer screening tests (trans-vaginal ultrasound plus a blood test called CA-125) only for women with a BRCA mutation or Lynch syndrome. These checks may help find this cancer but also produce many false-positive results according to the National Cancer Institute. 

Osteoporosis

Family link: If either of your parents fractured a hip, your odds of doing the same are 2.27 times higher than normal. 

What you can do: Ask about having a bone density test before age 65. Extra calcium and vitamin D, as well exercises that build muscle and endurance, can all help improve your bone density. 

Prostate Cancer

Family link: A man with one or more brothers who’ve had prostate cancer has three times the average risk of developing this cancer. The risk is doubled for a man whose father or any second-degree male relatives (uncles, cousins) had this cancer, report researchers from Belgium’s Hasselt University in a 2011 study.

What you can do: The ACS recommends men with a family history of prostate cancer in one first-degree relative before age 65 (father, brother or son) discuss prostate-cancer screening with their doctor at age 45. Have this talk at age 40 if more than one family member had prostate cancer. 

Vision Loss

Family link: One of the most common causes of vision loss is glaucoma. In this condition the optic nerve that delivers signals from your eyes to your brain is damaged, often by high fluid pressure in the eye. People with a family history of glaucoma are at four to nine times higher risk for developing the disease. And a family history of age-related macular degeneration (AMD) could raise your risk 10 to 27 times. With AMD, the area at the center of the retina becomes so blurry that clear, sharp central vision is lost.

What you can do: Ask your doc when you should get a complete eye check that includes dilating your pupils so that your doctor can examine your optic nerve and retina. 

Sari Harrar is an award-winning health, medicine and science journalist whose work appears in Dr. Oz The Good Life magazine, Good Housekeeping, O--Oprah Magazine, Organic Gardening and other publications.