The following criteria generally applies to most studies. Each item can have several variables and can change from study to study.


While many studies require both males and females, some studies will be gender specific i.e. males used for a male enhancement drug and females used for a birth control drug. Also, depending on where the clinic is at the time of screening, they may only need a certain gender. Some studies require an even split.


Every study will be targeted towards a specific age group. Example: 18 to 55 is common. May be you’ll see 25 to 45 or 65 to 80 or even 6 to 18.

The main age cut-offs are:

  1. 45 for most studies
  2. 55 for many studies
  3. 65 for some studies
  4. After 65, healthy Phase I studies will be limited but they do occur! These are usually the hardest to fill so compensation tends to be higher and referral bonuses are often offered.
  5. Studies for those 17 and under require parental permission

Body Mass Index (BMI)

Your height and weight are used to determine your BMI. Many studies recruit participants with a BMI between 18 to 30, but this figure can vary widely. BMI is your body fat. Click here to use a BMI calculator.

Ideal Body Weight

Many studies require you to be within a certain percentage. 15% is common. Click here to use a Ideal Body Weight Calculator. A study will use either the BMI or IBW but usually not both.

Multiply the ideal body weight by 15%. Then subtract your body weight from the ideal body weight. As long as your weight is equal to or less than 15% or what ever percentage the clinic is looking for, then you should be okay. Note that this is not a standard test and many clinics may use a different method.

Alcohol Use

Most studies require participants who do not consume alcohol in excess. Many studies will have “cut-off periods” of 24 to 72 hours before screening and check in and do not allow the consumption of alcohol during the study period. This includes the actual study as well as between multiple periods and out patient visits.

Do not show up at a clinic with a SCRAM ankle bracelet. Nothing says “I don’t have issues with alcohol” like showing up to a clinic with a Secure Continuous Remote Alcohol Monitoring device on your ankle. I have heard clinics banning volunteers who do this so don’t do it!

Tobacco Use

Most studies require participants who do not use tobacco products including chewing tobacco and cigarettes. Some studies do allow light users, but typically will ban the use of tobacco products during the length of the study. Note that some studies have “cut-off periods” of varying length. Many clinics are now doing blood tests for cotinine which is a byproduct of nicotine so it is best to be honest about whether or not you have smoked recently. Cut-off periods may range from a few days to a year or more. If you are exposed to heavy second hand smoke, you might test positive for cotinine and would be excluded.

Illicit Drug Use

All healthy volunteer studies require participants who do not use illicit drugs including but not limited to: crack, marijuana, cocaine, heroin and ecstasy. If you have put drugs behind you, be aware that most drugs can be traced in your system up to 90 days after cessation.

Many Clinical Research Facilities are implementing “Zero Tolerance” policies which allow them to bar you from participating in future studies if any illicit drugs are found in your system at any time during the study. This includes during the screening process, during the study and after the study until you have been “cleared” from the study.

Allergy History

It is necessary for the clinic to know if you are allergic to any drugs, foods or anything else. Having an allergy doesn’t necessarily exclude you from a study, but it is for your safety and health that you report any allergies you may have. Most studies have a study specific diet and cannot be altered due to food allergies. As for drug allergies, it is important that you don’t do studies with drugs that may cause an allergic reaction.

Prescription And Or Over-The-Counter Drug Use

Many studies require participants to not be taking prescription drugs or OTC drugs. Most studies will have “cut-off periods” of around 30 days. It is best to be honest if you have taken anything during the “cut-off period.” Anything found in your system that cannot be accounted for will most likely excluded you from the study. This also includes herbal and nutrition supplements as well as energy drinks which can throw off your labs.

Recent And Past Medical History

Most Clinical Research Facilities will ask information regarding your recent history. This can include any hospitalizations due to sickness or physical conditions, surgeries, mental conditions or medical procedures. Most surgeries will not disqualify you but it’s important for the clinic to know your history. This is generally collected at your first screening and updated as needed if you participate in additional studies.


Some studies require a certain ethnic population. Pretty unseal for Phase I but they occur.

Family History

Some studies will require subjects with no family history of certain conditions.

Recent Blood Or Plasma Donations

Depending on how often you donate blood or plasma, you may be asked to wait a period of time before participating in a study. You will not be allowed to donate blood or plasma during a study and usually for a period of 30 days after you complete a study. Participating in a clinical research study counts as blood donation.

Recent Involvement In A Clinical Research Study

Many volunteers find that they’ve enjoyed the experience of participating in a study so much that they want to join another study. Most studies have a “wash-out” of at least 30 days. That means that once you’ve completed your last dose in a study, you must wait at least 30 days before participating in another study at any clinic. Some studies will require a longer “wash-out” period. Many clinics are now using verification systems to check if you have been in another study recently.

More detailed explanation of washouts

International Travel

Many studies will have restrictions against people who have traveled outside the US or country that the study is being conducted in. This is due to unknown health conditions in foreign countries and especially if you had to have any vaccinations or immunizations.

Female Restrictions

Some studies will require surgically sterile or post menopausal participants. Also, females cannot be pregnant during a clinical research and should not conceive a child for a period of 3 months post study. 1st in man studies will generally require non-childbearing females or may not require females at all due to the unknown effects on pregnancy.

Your Availability

You must be available for all visits including staying at overnight for one or more consecutive or non-consecutive stays. You must be available for any and all out-patient visits. Dates are predetermined and are not negotiable. If you think you will not be able to make a visit, it is wise not to apply for that study. Failure to be on time and present for your visits can result in financial penalties. It is wise to also have a day or two on the tail end free. On rare occasions, studies may be delayed by a day or even postponed.

Part 1 – General Qualifications

Part 2 – In-Depth Look at Qualifications

Part 3 – Additional Requirements