To donate a kidney as a living donor, you must be at least 18 years old, be in good physical and mental health, and have adequate kidney function. Some transplant centers require donors to be at least 21. Beyond those basics, the evaluation process is thorough and can take several months, covering everything from blood work and imaging to psychological assessments and financial planning.
Age, BMI, and General Health
The minimum age is 18, though some hospitals set the bar at 21. There is no strict upper age limit, but older donors undergo more rigorous screening. Donors between 18 and 21 may face extra scrutiny because long-term health risks are harder to predict for younger people.
Body mass index matters. A BMI above 35 is generally considered an absolute disqualifier. A BMI between 30 and 35 falls into a gray area where your transplant center will weigh other factors before deciding. You need to be free of diabetes, including glucose intolerance, and your blood pressure should be under 140/90 without evidence of organ damage from hypertension.
Conditions That Disqualify You
Certain health conditions rule out donation entirely:
- Diabetes or glucose intolerance
- Significant heart disease
- Active or incompletely treated cancer
- Uncontrolled high blood pressure or hypertension that has already damaged organs
- Recurring kidney stones
- Significant protein in the urine, which signals kidney damage
Some conditions don’t automatically disqualify you but will get a closer look. These include a history of a single kidney stone, pre-diabetes in a young donor, a previous blood clot, a bleeding disorder, or a persistent infection. High blood pressure in younger donors or donors of non-Caucasian backgrounds is also flagged for additional evaluation because these groups face higher baseline risks of kidney disease over time.
Kidney Function Thresholds
Your kidneys’ filtering ability, measured as your glomerular filtration rate (GFR), is the single most important number in your evaluation. A GFR of 90 or above is considered acceptable for donation. If your GFR falls between 60 and 89, the transplant team will look at your full health profile and make an individualized decision. A GFR below 60 is a firm cutoff: you cannot donate.
GFR is typically measured through a 24-hour urine collection or specialized imaging with a tracer that shows how efficiently your kidneys clear waste. Your transplant center will use these results rather than relying on a simple blood creatinine level, which can be misleading on its own.
Blood Type Compatibility
Your blood type determines who you can donate to. The rules mirror blood transfusion compatibility:
- Type O donors can give to anyone (O, A, B, or AB)
- Type A donors can give to A or AB recipients
- Type B donors can give to B or AB recipients
- Type AB donors can only give to AB recipients
Recipients with type O blood can only receive from type O donors, making O kidneys the most in demand. Recipients with type AB can receive from any blood type.
If your blood type doesn’t match your intended recipient, you’re not necessarily out of options. A kidney paired exchange program lets two incompatible donor-recipient pairs swap, so each recipient gets a compatible kidney. The national system, run through the Organ Procurement and Transplantation Network, is open to all approved transplant programs that perform living donor kidney transplants.
The Medical Evaluation
Expect a comprehensive workup that typically includes blood tests, a 24-hour urine collection, an electrocardiogram to check heart rhythm, and a CT scan or MRI of your kidneys. The imaging maps the blood vessels feeding your kidneys and confirms both kidneys are structurally normal. Depending on your age and health history, additional cardiac testing or other specialty consultations may be added.
The evaluation process varies by center but often stretches over weeks to months. Multiple appointments are common. The transplant team is looking at the complete picture: not just whether your kidneys are healthy enough today, but whether removing one leaves you at an acceptable level of risk for the rest of your life.
Psychological and Social Evaluation
Every donor candidate undergoes a psychological assessment. The transplant team needs to confirm you’re mentally capable of making an informed decision and that no one is pressuring you into donating. Assessments typically cover your expectations about the process, your motivations, your relationship with the recipient, any history of psychiatric illness or substance use, and whether you have adequate social support for recovery.
The relationship between donor and recipient also gets attention. Strained or complicated dynamics can lead to negative emotional outcomes after surgery, so the team evaluates this throughout the process. If concerns come up, you may be offered counseling or additional psychological support rather than being immediately disqualified.
Recovery and Physical Demands
Kidney donation is major surgery, and the physical requirements extend beyond the operating room. Most donors stay in the hospital for one to two days. For the first four weeks, you cannot lift anything heavier than 20 pounds. Most donors return to work within two to four weeks, though this varies depending on the physical demands of your job.
You need to be in good enough health to tolerate general anesthesia and recover from a surgical procedure. If you have a physically demanding job or caregiving responsibilities, plan ahead for the recovery window.
Financial Considerations
The recipient’s insurance typically covers the donor’s medical evaluation, surgery, and immediate post-operative care. But it does not cover your lost wages, travel, childcare, or other non-medical costs. These out-of-pocket expenses can be a real barrier.
The National Living Donor Assistance Center (NLDAC) helps eligible donors with travel expenses, lost wages, and dependent care costs. Eligibility depends on your financial situation, and you apply through their program. It’s worth looking into early in the process, especially if taking time off work or traveling to the transplant center would be a hardship.
Long-Term Health Risks
Living with one kidney is safe for most donors, but the risks are not zero. Compared to similarly healthy people who didn’t donate, kidney donors have a higher long-term risk of developing end-stage kidney disease. One large study found the overall incidence was about 302 cases per million among donors, and the relative risk compared to matched non-donors was significantly elevated. Donors also face modestly increased risks of high blood pressure and cardiovascular issues over time.
These risks are still low in absolute terms, and most donors live long, healthy lives. But the transplant team factors your age, family history, ethnicity, and baseline health into their assessment precisely because these risks compound over decades. This is also why younger donors and those with even borderline risk factors receive extra scrutiny.